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FEATURES 20 MSPS Correlated Double Sampler (CDS) 4 dB 6 dB 6-Bit Pixel Gain Amplifier (PxGA(R)) 2 dB to 36 dB 10-Bit Variable Gain Amplifier (VGA) Low Noise Clamp Circuits Analog Preblanking Function 10-Bit (9841) or 12-Bit (9842) 20 MSPS A/D Converter Auxiliary Inputs with VGA and Input Clamp 3-Wire Serial Digital Interface 3 V Single Supply Operation Low Power: 65 mW @ 2.7 V Supply 48-Lead LQFP Package APPLICATIONS Digital Still Cameras Digital Video Camcorders
Complete 20 MSPS CCD Signal Processors AD9841A/AD9842A
PRODUCT DESCRIPTION
The AD9841A and AD9842A are complete analog signal processors for CCD applications. Both products feature a 20 MHz single-channel architecture designed to sample and condition the outputs of interlaced and progressive scan area CCD arrays. The AD9841A/AD9842A's signal chain consists of an input clamp, correlated double sampler (CDS), Pixel Gain Amplifier (PxGA), digitally controlled variable gain amplifier (VGA), black level clamp, and A/D converter. The AD9841A offers 10-bit ADC resolution, while the AD9842A contains a true 12-bit ADC. Additional input modes are provided for processing analog video signals. The internal registers are programmed through a 3-wire serial digital interface. Programmable features include gain adjustment, black level adjustment, input configuration, and power-down modes. The AD9841A and AD9842A operate from a single 3 V power supply, typically dissipate 78 mW, and are packaged in a 48lead LQFP.
FUNCTIONAL BLOCK DIAGRAM
PBLK AVDD AVSS HD VD CLPOB
4dB
6dB
COLOR STEERING 2dB-36dB 2:1 MUX
DRVDD CLP DRVSS
CCDIN
CDS
PxGA
10/12 VGA ADC DOUT
CLP 6 CLPDM 10 AUX1IN 2:1 MUX AUX2IN CLP CONTROL REGISTERS DVDD BUF 8 OFFSET DAC BANDGAP REFERENCE VRT VRB
INTERNAL BIAS
CML
AD9841A/AD9842A
SL
DIGITAL INTERFACE
INTERNAL TIMING
DVSS
SCK
SDATA
SHP
SHD
DATACLK
PxGA is a registered trademark of Analog Devices, Inc.
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Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 781/329-4700 World Wide Web Site: http://www.analog.com Fax: 781/326-8703 (c) Analog Devices, Inc., 2001
AD9841A/AD9842A-SPECIFICATIONS
GENERAL SPECIFICATIONS (T
Parameter TEMPERATURE RANGE Operating Storage POWER SUPPLY VOLTAGE Analog, Digital, Digital Driver POWER CONSUMPTION Normal Operation Power-Down Modes Fast Recovery Mode Standby Total Power-Down MAXIMUM CLOCK RATE A/D CONVERTER (AD9841A) Resolution Differential Nonlinearity (DNL) No Missing Codes Full-Scale Input Voltage Data Output Coding A/D CONVERTER (AD9842A) Resolution Differential Nonlinearity (DNL) No Missing Codes Full-Scale Input Voltage Data Output Coding VOLTAGE REFERENCE Reference Top Voltage (VRT) Reference Bottom Voltage (VRB)
Specifications subject to change without notice.
MIN
to TMAX, AVDD = DVDD = 3.0 V, fDATACLK = 20 MHz, unless otherwise noted.)
Min -20 -65 2.7 Typ Max +85 +150 3.6 Unit C C V
(Specified Under Each Mode of Operation) 30 5 1 20 10 0.4 10 2.0 Straight Binary 12 0.5 12 2.0 Straight Binary 2.0 1.0 1.0 1.0 mW mW mW MHz Bits LSB Bits Guaranteed V
Bits LSB Bits Guaranteed V
V V
DIGITAL SPECIFICATIONS (DRVDD = 2.7 V, C = 20 pF unless otherwise noted.)
L
Parameter LOGIC INPUTS High Level Input Voltage Low Level Input Voltage High Level Input Current Low Level Input Current Input Capacitance LOGIC OUTPUTS High Level Output Voltage, IOH = 2 mA Low Level Output Voltage, IOL = 2 mA
Specifications subject to change without notice.
Symbol VIH VIL IIH IIL CIN VOH VOL
Min 2.1
Typ
Max
Unit V V A A pF V V
0.6 10 10 10 2.2 0.5
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AD9841A/AD9842A AD9841A CCD-MODE SPECIFICATIONS wise noted.)
Parameter POWER CONSUMPTION
MAXIMUM CLOCK RATE CDS Gain Allowable CCD Reset Transient 1 Max Input Range Before Saturation 1 Max CCD Black Pixel Amplitude 1 PIXEL GAIN AMPLIFIER (PxGA) Max Input Range Max Output Range Gain Control Resolution Gain Monotonicity Gain Range (Two's Complement Coding) Min Gain (PxGA Gain Code 32) Max Gain (PxGA Gain Code 31) VARIABLE GAIN AMPLIFIER (VGA) Max Input Range Max Output Range Gain Control Resolution Gain Monotonicity Gain Range Low Gain (VGA Gain Code 91) Max Gain (VGA Gain Code 1023) BLACK LEVEL CLAMP Clamp Level Resolution Clamp Level Min Clamp Level Max Clamp Level SYSTEM PERFORMANCE Gain Accuracy, VGA Code 91 to 1023 2 PxGA Gain Accuracy Min Gain (PxGA Register Code 32) Max Gain (PxGA Code 31) Peak Nonlinearity, 500 mV Input Signal Peak Nonlinearity, 800 mV Input Signal Total Output Noise Power Supply Rejection (PSR) POWER-UP RECOVERY TIME Fast Recovery Mode Reference Standby Mode Total Shutdown Mode Power-Off Condition
NOTES 1 Input Signal Characteristics defined as follows:
(TMIN to TMAX, AVDD = DVDD = 3.0 V, fDATACLK = fSHP = fSHD = 20 MHz, unless otherMax Unit
mW MHz
Min
Typ
78
Notes
See TPC 1 for Power Curves
20 0 500 1.0 200 1.0 1.6 64 Guaranteed -2 10 1.6 2.0 . 1024 Guaranteed 2 36 256 0 63.75 -0.5 -1 11 0 12 0.1 0.4 0.2 40 0.1 1 3 15 +0.5 +1 13
dB mV V p-p mV V p-p V p-p Steps
See Input Waveform in Footnote 1 PxGA Gain at 4 dB
PxGA Gain at 4 dB At Any PxGA Gain
See Figure 28 for PxGA Gain Curve dB dB V p-p V p-p Steps See Figure 29 for VGA Gain Curve dB dB Steps Measured at ADC Output LSB LSB Specifications Include Entire Signal Chain Use Equations on Page 19 to Calculate Gain dB dB % % LSB rms dB ms ms ms ms VGA Gain Fixed at 2 dB (Code 91) VGA Gain Fixed at 2 dB (Code 91) 12 dB Gain Applied 8 dB Gain Applied AC Grounded Input, 6 dB Gain Applied Measured with Step Change on Supply Normal Clock Signals Applied
500mV TYP RESET TRANSIENT 200mV MAX OPTICAL BLACK PIXEL
2
1V MAX INPUT SIGNAL RANGE
PxGA gain fixed at 4 dB.
Specifications subject to change without notice.
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AD9841A/AD9842A-SPECIFICATIONS
AD9842A CCD-MODE SPECIFICATIONS
Parameter POWER CONSUMPTION
MAXIMUM CLOCK RATE CDS Gain Allowable CCD Reset Transient 1 Max Input Range Before Saturation 1 Max CCD Black Pixel Amplitude 1 PIXEL GAIN AMPLIFIER (PxGA) Max Input Range Max Output Range Gain Control Resolution Gain Monotonicity Gain Range (Two's Complement Coding) Min Gain (PxGA Gain Code 32) Max Gain (PxGA Gain Code 31) VARIABLE GAIN AMPLIFIER (VGA) Max Input Range Max Output Range Gain Control Resolution Gain Monotonicity Gain Range Low Gain (VGA Gain Code 91) Max Gain (VGA Gain Code 1023) BLACK LEVEL CLAMP Clamp Level Resolution Clamp Level Min Clamp Level Max Clamp Level SYSTEM PERFORMANCE Gain Accuracy, (VGA Code 91 to 1023) 2 PxGA Gain Accuracy Min Gain (PxGA Register Code 32) Max Gain (PxGA Code 31) Peak Nonlinearity, 500 mV Input Signal Total Output Noise Power Supply Rejection (PSR) POWER-UP RECOVERY TIME Fast Recovery Mode Reference Standby Mode Total Shutdown Mode Power-Off Condition
NOTES 1 Input Signal Characteristics defined as follows:
(TMIN to TMAX, AVDD = DVDD = 3.0 V, fDATACLK = fSHP = fSHD = 20 MHz, unless otherwise noted)
Max Unit
mW MHz
Min
Typ
78
Notes
See TPC 1 for Power Curves
20 0 500 1.0 200 1.0 1.6 64 Guaranteed -2 10 1.6 2.0 1024 Guaranteed 2 36 256 0 255 -0.5 -1 11 0 12 0.1 0.6 40 0.1 1 3 15 +0.5 +1 13
dB mV V p-p mV V p-p V p-p Steps
See Input Waveform in Footnote 1 PxGA Gain at 4 dB
See Figure 28 for PxGA Gain Curve dB dB V p-p V p-p Steps See Figure 29 for VGA Gain Curve dB dB Steps Measured at ADC Output LSB LSB Specifications Include Entire Signal Chain Use Equations on Page 19 to Calculate Gain dB dB % LSB rms dB ms ms ms ms VGA Gain Fixed at 2 dB (Code 91) VGA Gain Fixed at 2 dB (Code 91) 12 dB Gain Applied AC Grounded Input, 6 dB Gain Applied Measured with step change on supply Normal Clock Signals Applied
500mV TYP RESET TRANSIENT 200mV MAX OPTICAL BLACK PIXEL 1V MAX INPUT SIGNAL RANGE
2
PxGA gain fixed at 4 dB.
Specifications subject to change without notice.
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AD9841A/AD9842A AUX1-MODE SPECIFICATIONS
Parameter POWER CONSUMPTION MAXIMUM CLOCK RATE INPUT BUFFER Gain Max Input Range VGA Max Output Range Gain Control Resolution Gain (Selected Using VGA Gain Register) Min Gain Max Gain
Specifications subject to change without notice.
(TMIN to TMAX, AVDD = DVDD = 3.0 V, fDATACLK = 20 MHz, unless otherwise noted.)
Min Typ 60 20 0 1.0 2.0 1023 0 36 Max Unit mW MHz dB V p-p V p-p Steps dB dB
AUX2-MODE SPECIFICATIONS
Parameter POWER CONSUMPTION MAXIMUM CLOCK RATE INPUT BUFFER VGA Max Output Range Gain Control Resolution Gain (Selected Using VGA Gain Register) Min Gain Max Gain ACTIVE CLAMP (AD9841A) Clamp Level Resolution Clamp Level (Measured at ADC Output) Min Clamp Level Max Clamp Level ACTIVE CLAMP (AD9842A) Clamp Level Resolution Clamp Level (Measured at ADC Output) Min Clamp Level Max Clamp Level
Specifications subject to change without notice.
(TMIN to TMAX, AVDD = DVDD = 3.0 V, fDATACLK = 20 MHz, unless otherwise noted.)
Min Typ 60 20 (Same as AUX1-MODE) 2.0 512 0 18 256 0 63.75 256 0 255 V p-p Steps dB dB Steps LSB LSB Steps LSB LSB Max Unit mW MHz
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AD9841A/AD9842A TIMING SPECIFICATIONS Serial Timing in Figures 21-24.)
Parameter SAMPLE CLOCKS DATACLK, SHP, SHD Clock Period DATACLK Hi/Low Pulsewidth SHP Pulsewidth SHD Pulsewidth CLPDM Pulsewidth CLPOB Pulsewidth1 SHP Rising Edge to SHD Falling Edge SHP Rising Edge to SHD Rising Edge Internal Clock Delay Inhibited Clock Period DATA OUTPUTS Output Delay Output Hold Time Pipeline Delay SERIAL INTERFACE Maximum SCK Frequency SL to SCK Setup Time SCK to SL Hold Time SDATA Valid to SCK Rising Edge Setup SCK Falling Edge to SDATA Valid Hold SCK Falling Edge to SDATA Valid Read tCONV tADC tSHP tSHD tCDM tCOB tS1 tS2 tID tINH tOD tH
(CL = 20 pF, fSAMP = 20 MHz, CCD-Mode Timing in Figures 5 and 6, AUX-Mode Timing in Figure 7.
Symbol Min 48 20 7 7 4 2 0 20 10 14.5 7.6 9 16 Typ 50 25 12.5 12.5 10 20 12.5 25 3.0 Max Unit ns ns ns ns Pixels Pixels ns ns ns ns ns ns Cycles MHz ns ns ns ns ns
7.0
fSCLK tLS tLH tDS tDH tDV
10 10 10 10 10 10
NOTES 1 Minimum CLPOB pulsewidth is for functional operation only. Wider typical pulses are recommended to achieve low noise clamp performance. Specifications subject to change without notice.
ABSOLUTE MAXIMUM RATINGS With Respect To Min Max AVSS DVSS DRVSS DRVSS DVSS DVSS DVSS AVSS AVSS -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 -0.3 +3.9 +3.9 +3.9 DRVDD + 0.3 DVDD + 0.3 DVDD + 0.3 DVDD + 0.3 AVDD + 0.3 AVDD + 0.3 150 300
ORDERING GUIDE
Model
Unit V V V V V V V V V C C
Temperature Range
Package Description Thin Plastic Quad Flatpack (LQFP) Thin Plastic Quad Flatpack (LQFP)
Package Option ST-48
Parameter AVDD1, AVDD2 DVDD1, DVDD2 DRVDD Digital Outputs SHP, SHD, DATACLK CLPOB, CLPDM, PBLK SCK, SL, SDATA VRT, VRB, CMLEVEL BYP1-4, CCDIN Junction Temperature Lead Temperature (10 sec)
AD9841AJST -20C to +85C
AD9842AJST -20C to +85C
ST-48
THERMAL CHARACTERISTICS
Thermal Resistance 48-Lead LQFP Package JA = 92C
CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD9841A/AD9842A features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high-energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality.
WARNING!
ESD SENSITIVE DEVICE
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AD9841A/AD9842A
PIN CONFIGURATIONS
THREE-STATE DVSS DVDD2 VRB
THREE-STATE
SDATA SL NC STBY NC
SDATA SL
DVDD2 VRB
DVSS
NC STBY NC
VRT CML
SCK
48 47 46 45 44 43 42 41 40 39 38 37
48 47 46 45 44 43 42 41 40 39 38 37
NC 1 NC 2 (LSB) D0 3 D1 4 D2 5 D3 6 D4 7 D5 8 D6 9 D7 10 D8 11 (MSB) D9 12
PIN 1 IDENTIFIER
36 35
AUX1IN
(LSB) D0 1 D1 2 D2 3 D3 4 D4 5 D5 6 D6 7 D7 8 D8 9 D9 10 D10 11 (MSB) D11 12
CML
36 AUX1IN 35 AVSS 34 AUX2IN 33 AVDD2 32 BYP4 31 NC 30 CCDIN 29 BYP2 28 BYP1 27 AVDD1 26 AVSS 25 AVSS
SCK
AD9841A
TOP VIEW (Not to Scale)
AVSS 34 AUX2IN 33 AVDD2 32 BYP4
31
PIN 1 IDENTIFIER
NC 30 CCDIN
29
AD9842A
TOP VIEW (Not to Scale)
BYP2 28 BYP1 27 AVDD1
26
AVSS 25 AVSS
13 14 15 16 17 18 19 20 21 22 23 24
HD PBLK CLPOB SHP SHD
DRVSS DVSS DATACLK
DRVDD
CLPDM VD
DVDD1
SHP SHD
DVSS DATACLK
DRVDD
PIN FUNCTION DESCRIPTIONS Pin Number 1, 2 3-12 1-12 13 14 15, 41 16 17 18 19 20 21 22 23 24 25, 26, 35 27 28 29 30 31 32 33 34 36 37 38 39 40 42 43 44 45 46 47 48 Name NC D0-D9 D0-D11 DRVDD DRVSS DVSS DATACLK DVDD1 HD PBLK CLPOB SHP SHD CLPDM VD AVSS AVDD1 BYP1 BYP2 CCDIN NC BYP4 AVDD2 AUX2IN AUX1IN CML VRT VRB DVDD2 THREE-STATE NC STBY NC SL SDATA SCK Type NC DO DO P P P DI P DI DI DI DI DI DI DI P P AO AO AI NC AO P AI AI AO AO AO P DI NC DI NC DI DI DI Description Internally Not Connected (AD9841A ONLY) Digital Data Outputs (AD9841A ONLY) Digital Data Outputs (AD9842A ONLY) Digital Output Driver Supply Digital Output Driver Ground Digital Ground Digital Data Output Latch Clock Digital Supply Horizontal Drive. Used with VD for Color Steering Control Preblanking Clock Input Black Level Clamp Clock Input CDS Sampling Clock for CCD's Reference Level CDS Sampling Clock for CCD's Data Level Input Clamp Clock Input Vertical Drive. Used with HD for Color Steering Control Analog Ground Analog Supply Internal Bias Level Decoupling Internal Bias Level Decoupling Analog Input for CCD Signal Internally Not Connected Internal Bias Level Decoupling Analog Supply Analog Input Analog Input Internal Bias Level Decoupling A/D Converter Top Reference Voltage Decoupling A/D Converter Bottom Reference Voltage Decoupling Digital Supply Digital Output Disable. Active High May be tied high or low. Do not leave floating. Standby Mode, Active High. Same as Serial Interface Internally Not Connected. May be Tied High or Low Serial Digital Interface Load Pulse Serial Digital Interface Data Serial Digital Interface Clock
TYPE: AI = Analog Input, AO = Analog Output, DI = Digital Input, DO = Digital Output, P = Power.
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CLPDM VD
HD PBLK CLPOB
DRVSS
DVDD1
NC = NO CONNECT
NC = NO CONNECT 13 14 15 16 17 18 19 20 21 22 23 24
VRT
AD9841A/AD9842A
DEFINITIONS OF SPECIFICATIONS
DIFFERENTIAL NONLINEARITY (DNL)
An ideal ADC exhibits code transitions that are exactly 1 LSB apart. DNL is the deviation from this ideal value. Thus every code must have a finite width. No missing codes guaranteed to 12-bit resolution indicates that all 4096 codes, respectively, must be present over all operating conditions.
PEAK NONLINEARITY
in LSB, and represents the rms noise level of the total signal chain at the specified gain setting. The output noise can be converted to an equivalent voltage, using the relationship 1 LSB = (ADC Full Scale/2N codes) when N is the bit resolution of the ADC. For the AD9842A, 1 LSB is 500 V, and for the AD9841A, 1 LSB is 2 mV.
POWER SUPPLY REJECTION (PSR)
Peak nonlinearity, a full signal chain specification, refers to the peak deviation of the output of the AD984x from a true straight line. The point used as "zero scale" occurs 1/2 LSB before the first code transition. "Positive full scale" is defined as a Level 1, 1/2 LSB beyond the last code transition. The deviation is measured from the middle of each particular output code to the true straight line. The error is then expressed as a percentage of the 2 V ADC full-scale signal. The input signal is always appropriately gained up to fill the ADC's full-scale range.
TOTAL OUTPUT NOISE
The PSR is measured with a step change applied to the supply pins. This represents a very high frequency disturbance on the AD984xA's power supply. The PSR specification is calculated from the change in the data outputs for a given step change in the supply voltage.
INTERNAL DELAY FOR SHP/SHD
The rms output noise is measured using histogram techniques. The standard deviation of the ADC output codes is calculated
EQUIVALENT INPUT CIRCUITS
DVDD
The internal delay (also called aperture delay) is the time delay that occurs from when a sampling edge is applied to the AD984xA until the actual sample of the input signal is held. Both SHP and SHD sample the input signal during the transition from low to high, so the internal delay is measured from each clock's rising edge to the instant the actual internal sample is taken.
ACVDD
330
60
ACVSS
ACVSS
DVSS
Figure 1. Digital Inputs--SHP, SHD, DATACLK, CLPOB, CLPDM, HD, VD, PBLK, SCK, SL
DVDD DRVDD
Figure 3. CCDIN (Pin 30)
DATA
DVDD
DVDD
DATA IN
THREESTATE
DOUT
DATA OUT
330
RNW
DVSS DVSS
DVSS DRVSS
DVSS
Figure 2. Data Outputs--D0-D9 (D11)
Figure 4. SDATA (Pin 47)
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Typical Performance Characteristics- AD9841A/AD9842A
100
0.5
90
POWER DISSIPATION - mW
80
VDD = 3.3V
0.25
70
VDD = 3.0V VDD = 2.7V
0
60
-0.25
50
40 5 15 10 SAMPLE RATE - MHz 20
-0.5 0 500 1000 1500 2000 2500 3000 3500 4000
TPC 1. AD9841A/AD9842A Power vs. Sample Rate
TPC 4. AD9842A Typical DNL Performance
0.5
15
0.25
OUTPUT NOISE - LSB
0 200 400 600 800 1000
10
0
5
-0.25
-0.5
0 0 200 600 400 VGA GAIN CODE - LSB 800 1000
TPC 2. AD9841A Typical DNL Performance
TPC 5. AD9842A Output Noise vs. VGA Gain
4
3
OUTPUT NOISE - LSB
2
1
0 0 200 400 600 VGA GAIN CODE - LSB 800 1000
TPC 3. AD9841A Output Noise vs. VGA Gain
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AD9841A/AD9842A
CCD-MODE AND AUX MODE TIMING
CCD SIGNAL
tID
N
N+1
N+2
N+9
N+10
tID
SHP
tS1
SHD
tS2
tCP
tINH
DATACLK
tOD
OUTPUT DATA N-10 N-9
tH
N-8 N-1 N
NOTES: 1. RECOMMENDED PLACEMENT FOR DATACLK RISING EDGE IS BETWEEN THE SHD RISING EDGE AND NEXT SHP FALLING EDGE. 2. CCD SIGNAL IS SAMPLED AT SHP AND SHD RISING EDGES.
Figure 5. CCD-Mode Timing
EFFECTIVE PIXELS
OPTICAL BLACK PIXELS
HORIZONTAL BLANKING
DUMMY PIXELS
EFFECTIVE PIXELS
CCD SIGNAL
CLPOB
CLPDM
PBLK
OUTPUT DATA
EFFECTIVE PIXEL DATA
OB PIXEL DATA
DUMMY BLACK
EFFECTIVE DATA
NOTES: 1. CLPOB AND CLPDM WILL OVERWRITE PBLK. PBLK WILL NOT AFFECT CLAMP OPERATION IF OVERLAPPING CLPDM AND/OR CLPOB. 2. PBLK SIGNAL IS OPTIONAL. 3. DIGITAL OUTPUT DATA WILL BE ALL ZEROS DURING PBLK. OUTPUT DATA LATENCY IS 9 DATACLK CYCLES.
Figure 6. Typical CCD-Mode Line Clamp Timing
N VIDEO SIGNAL
N+9 N+1
tID tCP
N+8 N+2
DATACLK
tOD
OUTPUT DATA N-10 N-9
tH
N-8 N-1 N
Figure 7. AUX-Mode Timing
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AD9841A/AD9842A
PIXEL GAIN AMPLIFIER (PxGA) TIMING
VD 0101... HD LINE 0 2323... LINE 1
FRAME n
FRAME n+1
0101... LINE 2 LINE m-1 LINE m
0101... LINE 0
2323... LINE 1
0101... LINE 2 LINE m-1 LINE m
NOTE: 0 = GAIN0, 1 = GAIN1, 2 = GAIN2, 3 = GAIN3
Figure 8. PxGA Mode 1 (Mosaic Separate) Frame/Line Gain Register Sequence
5 PIXEL MIN VD
HD 3ns MIN 3ns MIN
SHP
PxGA GAIN
GAINX
GAIN0
GAIN1
GAIN0
GAINX
GAIN2
GAIN3
NOTES: 1. MINIMUM PULSEWIDTH FOR HD AND VD IS 5 PIXEL CYCLES. 2. BOTH VD AND HD ARE INTERNALLY UPDATED AT SHP RISING EDGES. MINIMUM SET-UP TIME IS 3ns. 3. EVERY HD RISING EDGE WITH A PREVIOUS VD RISING EDGE WILL RESET TO 0101. 4. EVERY HD RISING EDGE WITHOUT A PREVIOUS VD RISING EDGE WILL ALTERNATE BETWEEN 0101... AND 2323.
Figure 9. PxGA Mode 1 (Mosaic Separate) Detailed Timing
VD
EVEN FIELD
ODD FIELD
0101... HD LINE 0
2323... LINE 1
0101... LINE 2 LINE m-1 LINE m
0101... LINE 0
2323... LINE 1
0101... LINE 2 LINE m-1 LINE m
NOTE: 0 = GAIN0, 1 = GAIN1, 2 = GAIN2, 3 = GAIN3
Figure 10. PxGA Mode 2 (Interlace) Frame/Line Gain Register Sequence
VD
5 PIXEL MIN HD 3ns MIN 3ns MIN
SHP
PxGA GAIN
GAINX
GAIN0
GAIN1
GAIN0
GAINX
GAIN2
GAIN3
NOTES: 1. BOTH VD AND HD ARE INTERNALLY UPDATED AT SHP RISING EDGES. 2. EVERY HD RISING EDGE WITH A PREVIOUS VD RISING OR FALLING EDGE WILL RESET TO 0101. 3. EVERY HD RISING EDGE WITHOUT A PREVIOUS VD RISING EDGE WILL ALTERNATE BETWEEN 0101... AND 2323.
Figure 11. PxGA Mode 2 (Interlace) Detailed Timing
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AD9841A/AD9842A
VD LINE n LINE n+1
012012012... HD NOTE: 0 = GAIN0, 1 = GAIN1, 2 = GAIN2
...01201
012012012...
Figure 12. PxGA Mode 3 (3-Color) Frame/Line Gain Register Sequence
5 PIXEL MIN VD
5 PIXEL MIN HD 3ns MIN
SHP
PxGA GAIN
GAINX
GAIN0
GAIN1
GAIN2
GAIN0
GAINX
GAIN0
GAIN1
NOTES: 1. BOTH VD AND HD ARE INTERNALLY UPDATED AT SHP RISING EDGES. 2. EVERY HD RISING EDGE WITH A PREVIOUS VD RISING EDGE WILL RESET TO 012012.
Figure 13. PxGA Mode 3 (3-Color) Detailed Timing
VD
LINE n
LINE n+1
01230123012... HD NOTE: 0 = GAIN0, 1 = GAIN1, 2 = GAIN2, 3 = GAIN3
...01230
012301230123...
Figure 14. PxGA Mode 4 (4-Color) Frame/Line Gain Register Sequence
5 PIXEL MIN VD
5 PIXEL MIN HD 3ns MIN
SHP
PxGA GAIN
GAINX
GAIN0
GAIN1
GAIN2
GAIN0
GAINX
GAIN0
GAIN1
NOTES: 1. BOTH VD AND HD ARE INTERNALLY UPDATED AT SHP RISING EDGES. 2. EVERY HD RISING EDGE WITH A PREVIOUS VD RISING EDGE WILL RESET TO 01230123.
Figure 15. PxGA Mode 4 (4-Color) Detailed Timing
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AD9841A/AD9842A
VD 0101... LINE 1 ODD FIELD EVEN FIELD 0101... HD LINE 0 0101... LINE 2 LINE m-1 LINE m 2323... LINE 0 2323... LINE 1 2323... LINE 2 LINE m-1 LINE m
NOTE: 0 = GAIN0, 1 = GAIN1, 2 = GAIN2, 3 = GAIN3
Figure 16. PxGA Mode 5 (VD Selected) Frame/Line Gain Register Sequence
VD
5 PIXEL MIN HD 3ns MIN 3ns MIN
SHP
PxGA GAIN
GAINX
GAIN0
GAIN1
GAIN0
GAINX
GAIN2
GAIN3
NOTES: 1. BOTH VD AND HD ARE INTERNALLY UPDATED AT SHP RISING EDGES. 2. EVERY HD RISING EDGE WITH A PREVIOUS VD FALLING EDGE WILL RESET TO 0101. 3. EVERY HD RISING EDGE WITH A PREVIOUS VD RISING EDGE WILL RESET TO 2323. 4. EVERY HD RISING EDGE WITHOUT A PREVIOUS VD RISING EDGE WILL REPEAT EITHER 0101... (EVEN) OR 2323 ... (ODD).
Figure 17. PxGA Mode 5 (VD Selected) Detailed Timing
VD 0101... HD LINE 0 1212... LINE 1
FRAME n 1212... LINE 1
FRAME n+1 0101... LINE 2 LINE m-1 LINE m
0101... LINE 2 LINE m-1 LINE m
0101... LINE 0
NOTE: 0 = GAIN0, 1 = GAIN1, 2 = GAIN2
Figure 18. PxGA Mode 6 (Mosaic Repeat) Frame/Line Gain Register Sequence
5 PIXEL MIN VD
HD 3ns MIN
3ns MIN
SHP
PxGA GAIN
GAINX
GAIN0
GAIN1
GAIN0
GAINX
GAIN1
GAIN2
NOTES: 1. MINIMUM PULSEWIDTH FOR HD AND VD IS 5 PIXEL CYCLES. 2. BOTH VD AND HD ARE INTERNALLY UPDATED AT SHP RISING EDGES. MINIMUM SET-UP TIME IS 3ns. 3. EVERY HD RISING EDGE WITH A PREVIOUS VD RISING EDGE WILL RESET TO 0101. 4. EVERY HD RISING EDGE WITHOUT A PREVIOUS VD RISING EDGE WILL ALTERNATE BETWEEN 0101... AND 1212.
Figure 19. PxGA Mode 6 (Mosaic Repeat) Detailed Timing
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AD9841A/AD9842A
VD
HD
3ns MIN
3ns MIN
SHP
PxGA GAIN
GAIN0
GAIN1
GAIN0
GAIN2
GAIN3
NOTES: 1. BOTH VD AND HD ARE INTERNALLY UPDATED AT SHP RISING EDGES. 2. VD = 0 AND HD = 0 SELECTS GAIN0. 3. VD = 0 AND HD = 1 SELECTS GAIN1. 4. VD = 1 AND HD = 0 SELECTS GAIN2. 5. VD = 1 AND HD = 1 SELECTS GAIN3.
Figure 20. PxGA Mode 7 (User-Specified) Detailed Timing
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AD9841A/AD9842A
SERIAL INTERFACE TIMING AND INTERNAL REGISTER DESCRIPTION Table I. AD9841A/AD9842A Internal Register Map
Register Name
Operation VGA Gain Clamp Level Control PxGA Gain0 PxGA Gain1 PxGA Gain2 PxGA Gain3
Address A0 A1 A2
0 1 0 1 0 1 0 1 0 0 1 1 0 0 1 1 0 0 0 0 1 1 1 1
D0
D1
D2
Data Bits D3 D4
D5
D6
0*
D7
1**
D8
0*
D9
0* MSB
D10
0* X X X X X X X
Channel Select Power-Down CCD/AUX1/2 Modes LSB LSB Color Steering Mode Selection LSB LSB LSB LSB PxGA On/Off
Software OB Clamp Reset On/Off
MSB Clock Polarity Select for SHP/SHD/CLP/DATA MSB MSB MSB MSB X X X X 0* X X X X
X 0* X X X X
X ThreeState X X X X
*Internal use only. Must be set to zero. **Must be set to one.
RNW SDATA 0 A0 A1 A2
TEST BIT 0 D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10
tDS
SCK
tDH
tLS
SL NOTES: 1. SDATA BITS ARE INTERNALLY LATCHED ON THE RISING EDGES OF SCK. 2. RNW = READ-NOT WRITE. SET LOW FOR WRITE OPERATION. 3. TEST BITS = INTERNAL USE ONLY. MUST BE SET LOW. 4. SYSTEM UPDATE OF LOADED REGISTERS OCCURS ON SL RISING EDGE.
tLH
Figure 21. Serial Write Operation
RNW SDATA 1 A0 A1 0
TEST BIT 0 D0 D1 D2 D3 D4 D5 D6 D7 D8 D9 D10
tDS
SCK
tDH
tDV
tLS
SL
tLH
NOTES: 1. RNW = READ-NOT WRITE. SET HIGH FOR READ OPERATION. 2. TEST BITS = INTERNAL USE ONLY. MUST BE SET LOW. 3. SERIAL DATA FROM THE SELECTED REGISTER IS VALID STARTING AFTER THE 5TH SCK FALLING EDGE, AND IS UPDATED ON SCK FALLING EDGES.
Figure 22. Serial Readback Operation
REV. 0
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AD9841A/AD9842A
RNW A0 A1 SDATA 0 0 0 A2 0 0 11 BITS OPERATION D0 ... 10 BITS ACG GAIN ... D9 8 BITS CLAMP LEVEL D0 ... D7 10 BITS CONTROL D0 ... D9 6 BITS PxGA GAIN0 D0 ... D5 6 BITS PxGA GAIN1 D0 ... D5 6 BITS PxGA GAIN2 D0 ... D5 6 BITS PxGA GAIN3 D0 ... D5
D10 D0
SCK 1 SL 2 3 4 5 6
... 16 17
... 26 27
... 34 35
... 44 45
... 50 51
... 56 57
... 62 63
... 68
...
NOTES: 1. ANY NUMBER OF ADJACENT REGISTERS MAY BE LOADED SEQUENTIALLY, BEGINNING WITH THE LOWEST ADDRESS AND INCREMENTING ONE ADDRESS AT A TIME. 2. WHEN SEQUENTIALLY LOADING MULTIPLE REGISTERS, THE EXACT REGISTER LENGTH (SHOWN ABOVE) MUST BE USED FOR EACH REGISTER. 3. ALL LOADED REGISTERS WILL BE SIMULTANEOUSLY UPDATED WITH THE RISING EDGE OF SL.
Figure 23. Continuous Serial Write Operation to All Registers
RNW SDATA 0
A0 0
A1 0
A2 1 0 D0 D1
PxGA GAIN0 D2 D3 D4 D5 D0 D1
PxGA GAIN1 D2 D3 D4 D5
PxGA GAIN2 D0 ... D5
PxGA GAIN3 D0 ... D5
SCK 1 SL 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18
... 23 24
... 29
...
Figure 24. Continuous Serial Write Operation to All PxGA Gain Registers
Table II. Operation Register Contents (Default Value x000) D10 D9 0* 0* D8 0* D7 D6 Optical Black Clamp D5 0 Enable Clamping 1 Disable Clamping Reset D4 0 Normal 1 Reset All Registers to Default Power-Down Modes D3 D2 0 0 1 1 0 1 0 1 Normal Power Fast Recovery Standby Total Power-Down Channel Selection D1 D0 0 0 1 1 0 1 0 1 CCD Mode AUX1 Mode AUX2 Mode Test Only
1** 0*
*Must be set to zero. **Set to one.
Table III. VGA Gain Register Contents (Default Value x096) D10 X MSB D9 0 D8 0 D7 0 D6 1 D5 0 * * * 1 1 D4 1 D3 1 D2 1 D1 1 LSB D0 1 Gain (dB) 2.0 * * * 35.965 36.0
1 1
1 1
1 1
1 1
1 1
1 1
1 1
1 1
0 1
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AD9841A/AD9842A
Table IV. AD9841A Clamp Level Register Contents (Default Value x080) D10 X D9 X D8 X MSB D7 0 0 0 D6 0 0 0 D5 0 0 0 D4 0 0 0 * * * 1 1 1 1 1 1 1 0 D3 0 0 0 D2 0 0 0 D1 0 0 1 LSB D0 0 1 0 Clamp Level (LSB) 0 0.25 0.5 * * * 63.5
1
1
1
1
1
1
1
1
63.75
Table V. AD9842A Clamp Level Register Contents (Default Value x080) D10 X D9 X D8 X MSB D7 0 0 0 D6 0 0 0 D5 0 0 0 D4 0 0 0 * * * 1 1 1 1 1 1 1 0 D3 0 0 0 D2 0 0 0 D1 0 0 1 LSB D0 0 1 0 Clamp Level (LSB) 0 1 2 * * * 254
1
1
1
1
1
1
1
1
255
Table VI. Control Register Contents (Default Value x000) D10 Data Out D9 DATACLK D8 D7 D6 CLP/PBLK D5 SHP/SHD D4 PxGA D3** Color Steering Modes D2 D1 D0
X
0 Enable 1 Three-State
0*
0*
0 Rising Edge Trigger 0 Active Low 0 Active Low 1 Falling Edge Trigger 1 Active High 1 Active High
0 Disable 0 1 Enable 0 0 0 1 1 1 1
0 0 1 1 0 0 1 1
0 1 0 1 0 1 0 1
Steering Disabled Mosaic Separate Interlace 3-Color 4-Color VD Selected Mosaic Repeat User Specified
*Must be set to zero. **When D3 = 0 (PxGA disabled) the PxGA gain is fixed to 4 dB.
Table VII. PxGA Gain Registers for Gain0, Gain1, Gain2, Gain3 (Default Value x000) D10 D9 D8 D7 D6 MSB D5 D4 D3 D2 D1 LSB D0 Gain (dB)*
X
X
X
X
X
0
1
1
* * *
1
1
1
+10.0
* * *
0 1
0 1
0 1
* * *
0 1
0 1
0 1
+4.3 +4.0
* * *
1
0
0
0
0
0
-2.0
*Control Register Bit D3 must be set High (PxGA Enable) to use the PxGA Gain Registers.
REV. 0
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AD9841A/AD9842A
CIRCUIT DESCRIPTION AND OPERATION
The AD9841A and AD9842A signal processing chain is shown in Figure 25. Each processing step is essential in achieving a high-quality image from the raw CCD pixel data.
DC Restore
To reduce the large dc offset of the CCD output signal, a dcrestore circuit is used with an external 0.1 F series coupling capacitor. This restores the dc level of the CCD signal to approximately 1.5 V, to be compatible with the 3 V single supply of the AD984xA.
Correlated Double Sampler
effect of a gain change on the system black level, usually called the "gain step." Another advantage of removing this offset at the input stage is to maximize system headroom. Some area CCDs have large black level offset voltages, which, if not corrected at the input stage, can significantly reduce the available headroom in the internal circuitry when higher VGA gain settings are used. Horizontal timing is shown in Figure 6. It is recommended that the CLPDM pulse be used during valid CCD dark pixels. CLPDM may be used during the optical black pixels, either together with CLPOB or separately. The CLPDM pulse should be a minimum of 4 pixels wide.
PxGA
The CDS circuit samples each CCD pixel twice to extract the video information and reject low-frequency noise. The timing shown in Figure 5 illustrates how the two CDS clocks, SHP and SHD, are used to sample the reference level and data level of the CCD signal respectively. The CCD signal is sampled on the rising edges of SHP and SHD. Placement of these two clock signals is critical in achieving the best performance from the CCD. An internal SHP/SHD delay (tID) of 3 ns is caused by internal propagation delays.
Input Clamp
A line-rate input clamping circuit is used to remove the CCD's optical black offset. This offset exists in the CCD's shielded black reference pixels. Unlike some AFE architectures, the AD984xA removes this offset in the input stage to minimize the
The PxGA provides separate gain adjustment for the individual color pixels. A programmable gain amplifier with four separate values, the PxGA has the capability to "multiplex" its gain value on a pixel-to-pixel basis. This allows lower output color pixels to be gained up to match higher output color pixels. Also, the PxGA may be used to adjust the colors for white balance, reducing the amount of digital processing that is needed. The four different gain values are switched according to the "Color Steering" circuitry. Seven different color steering modes for different types of CCD color filter arrays are programmed in the AD984xA's Control Register. For example, Mosaic Separate steering mode accommodates the popular "Bayer" arrangement of Red, Green, and Blue filters (see Figure 26).
VD HD
COLOR STEERING 2
3
PxGA MODE SELECTION
GAIN0 4:1 MUX DC RESTORE 6 GAIN1 GAIN2 GAIN3 2dB TO 36dB 0.1 F CCDIN CDS
PxGA
PxGA GAIN REGISTERS INTERNAL VREF 2V FULL SCALE 10-/12-BIT ADC 10/12 DOUT
VGA
-2dB TO +10dB
INPUT OFFSET CLAMP CLPDM
10
8-BIT DAC
OPTICAL BLACK CLAMP DIGITAL FILTERING 8 CLAMP LEVEL REGISTER
CLPOB
VGA GAIN REGISTER
Figure 25. AD9841A/AD9842A CCD-Mode Block Diagram
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AD9841A/AD9842A
CCD: PROGRESSIVE BAYER R Gb R Gb Gr B Gr B R Gb R Gb Gr B Gr B LINE0 LINE1 LINE2 MOSAIC SEPARATE COLOR STEERING MODE GAIN0, GAIN1, GAIN0, GAIN1 ... GAIN2, GAIN3, GAIN2, GAIN3 ... GAIN0, GAIN1, GAIN0, GAIN1 ...
is needed to match a 1 V input signal with the ADC full-scale range of 2 V. When compared to 1 V full-scale systems (such as ADI's AD9803), the equivalent gain range is 0 dB to 34 dB. The VGA gain curve is divided into two separate regions. When the VGA Gain Register code is between 0 and 511, the curve follows a (1 + x)/(1 - x) shape, which is similar to a "linear-indB" characteristic. From code 512 to code 1023, the curve follows a "linear-in-dB" shape. The exact VGA gain can be calculated for any Gain Register value by using the following two equations: Code Range 0-511 512 -1023 Gain Equation (dB) Gain = 20 log10 ([658 + code]/[658 - code]) - 0.4 Gain = (0.0354)(code) - 0.4
Figure 26. CCD Color Filter Example: Progressive Scan
CCD: INTERLACED BAYER EVEN FIELD R R R R Gr Gr Gr Gr R R R R Gr Gr Gr Gr LINE0 LINE1 LINE2 VD SELECTED COLOR STEERING MODE GAIN0, GAIN1, GAIN0, GAIN1 ... GAIN0, GAIN1, GAIN0, GAIN1 ... GAIN0, GAIN1, GAIN0, GAIN1 ...
As shown in the CCD Mode Specifications, only the VGA gain range from 2 dB to 36 dB has tested and guaranteed accuracy. This corresponds to a VGA gain code range of 91 to 1023. The Gain Accuracy Specifications also include the PxGA gain of 4 dB, for a total gain range of 6 dB to 40 dB.
36
ODD FIELD Gb Gb Gb Gb B B B B Gb Gb Gb Gb B B B B LINE0 LINE1 LINE2 GAIN2, GAIN3, GAIN2, GAIN3 ...
30
GAIN2, GAIN3, GAIN2, GAIN3 ... VGA GAIN - dB GAIN2, GAIN3, GAIN2, GAIN3 ...
24
18
Figure 27. CCD Color Filter Example: Interlaced
The same Bayer pattern can also be interlaced, and the VD Selected mode should be used with this type of CCD (see Figure 27). The Color Steering performs the proper multiplexing of the R, G, and B gain values (loaded into the PxGA gain registers), and is synchronized by the user with vertical (VD) and horizontal (HD) sync pulses. For more detailed information, see the PxGA Timing section. The PxGA gain for each of the four channels is variable from -2 dB to +10 dB, controlled in 64 steps through the serial interface. The PxGA gain curve is shown in Figure 28.
10
12
6
0
0
127
255 383 511 639 767 VGA GAIN REGISTER CODE
895
1023
Figure 29. VGA Gain Curve (Gain from PxGA Not Included)
Optical Black Clamp
8
PxGA GAIN - dB
6
4
2
0
-2 32 (100000)
40
48
56
0
8
16
24
31 (011111)
PxGA GAIN REGISTER CODE
The optical black clamp loop is used to remove residual offsets in the signal chain, and to track low-frequency variations in the CCD's black level. During the optical black (shielded) pixel interval on each line, the ADC output is compared with a fixed black level reference, selected by the user in the Clamp Level Register. Any value between 0 LSB and 64 LSB (AD9841A) or 255 LSB (AD9842A) may be programmed, with 8-bit resolution. The resulting error signal is filtered to reduce noise, and the correction value is applied to the ADC input through a D/A converter. Normally, the optical black clamp loop is turned on once per horizontal line, but this loop can be updated more slowly to suit a particular application. If external digital clamping is used during the post processing, the AD984xA's optical black clamping may be disabled using Bit D5 in the Operation Register (see Serial Interface Timing and Internal Register Description section). When the loop is disabled, the Clamp Level Register may still be used to provide programmable offset adjustment. Horizontal timing is shown in Figure 6. The CLPOB pulse should be placed during the CCD's optical black pixels. It is recommended that the CLPOB pulse duration be at least 20 pixels wide to minimize clamp noise. Shorter pulsewidths may be used, but clamp noise may increase, and the ability to track low-frequency variations in the black level will be reduced.
Figure 28. PxGA Gain Curve
Variable Gain Amplifier
The VGA stage provides a gain range of 2 dB to 36 dB, programmable with 10-bit resolution through the serial digital interface. Combined with 4 dB from the PxGA stage, the total gain range for the AD984xA is 6 dB to 40 dB. The minimum gain of 6 dB REV. 0
-19-
AD9841A/AD9842A
A/D Converter
The AD9841A and AD9842A use high-performance ADC architectures, optimized for high speed and low power. Differential Nonlinearity (DNL) performance is typically better than 0.5 LSB, as shown in TPCs 2 and 4. Instead of the 1 V full-scale range used by the earlier AD9801 and AD9803 products from Analog Devices, the AD984xA ADCs use a 2 V input range. Better noise performance results from using a larger ADC full-scale range (see TPCs 3 and 5).
AUX1 Mode
Figure 29). The VGA gains up the signal level with respect to the 0.4 V bias level. Signal levels above the bias level will be further increased to a higher ADC code, while signal levels below the bias level will be further decreased to a lower ADC code.
AUX2 Mode
For applications that do not require CDS, the AD9841A/AD9842A can be configured to sample ac-coupled waveforms. Figure 30 shows the circuit configuration for using the AUX1 channel input (Pin 36). A single 0.1 F ac-coupling capacitor is needed between the input signal driver and the AUX1IN pin. An on-chip dc-bias circuit sets the average value of the input signal to approximately 0.4 V, which is referenced to the midscale code of the ADC. The VGA Gain register provides a gain range of 0 dB to 36 dB in this mode of operation (see VGA Gain Curve,
For sampling video-type waveforms, such as NTSC and PAL signals, the AUX2 channel provides black level clamping, gain adjustment, and A/D conversion. Figure 31 shows the circuit configuration for using the AUX2 channel input (Pin 34). A external 0.1 F blocking capacitor is used with the on-chip video clamp circuit, to level-shift the input signal to a desired reference level. The clamp circuit automatically senses the most negative portion of the input signal, and adjusts the voltage across the input capacitor. This forces the black level of the input signal to be equal to the value programmed into the Clamp Level register (see Serial Interface Register Description). The VGA provides gain adjustment from 0 dB to 18 dB. The same VGA Gain register is used, but only the 9 MSBs of the gain register are used (see Table VIII.)
0.8V
??V
0.4V 5k 0dB TO 36dB
0.1 F INPUT SIGNAL
AUX1IN VGA ADC MIDSCALE
0.4V
0.4V
10 VGA GAIN REGISTER
Figure 30. AUX1 Circuit Configuration
VGA GAIN REGISTER 9 BUFFER VIDEO SIGNAL AUX2IN VGA 0.1 F VIDEO CLAMP CIRCUIT LPF 8 CLAMP LEVEL REGISTER CLAMP LEVEL ADC 0dB TO 18dB
Figure 31. AUX2 Circuit Configuration
Table VIII. VGA Gain Register Used for AUX2-Mode
D10 X
MSB D9 0 1
D8 X 0
D7 X 0
D6 X 0
D5 X 0 * * * 1
D4 X 0
D3 X 0
D2 X 0
D1 X 0
LSB D0 X 0
Gain (dB) 0.0 0.0 * * * 18.0 REV. 0
1
1
1
1
1 -20-
1
1
1
1
AD9841A/AD9842A
APPLICATIONS INFORMATION
The AD9841A and AD9842A are complete Analog Front End (AFE) products for digital still camera and camcorder applications. As shown in Figure 32, the CCD image (pixel) data is buffered and sent to the AD984xA analog input through a series input capacitor. The AD984xA performs the dc restoration, CDS, gain adjustment, black level correction, and analog-to-
digital conversion. The AD984xA's digital output data is then processed by the image processing ASIC. The internal registers of the AD984xA--used to control gain, offset level, and other functions--are programmed by the ASIC or microprocessor through a 3-wire serial digital interface. A system timing generator provides the clock signals for both the CCD and the AFE.
CCD VOUT 0.1 F
AD984xA
ADCOUT CCDIN REGISTER DATA BUFFER CDS/CLAMP TIMING CCD TIMING TIMING GENERATOR
DIGITAL OUTPUTS SERIAL INTERFACE DIGITAL IMAGE PROCESSING ASIC
V-DRIVE
Figure 32. AD984xA System Applications Diagram
3V ANALOG SUPPLY 0.1 F 1.0 F SERIAL INTERFACE 3 1.0 F
NC THREE-STATE DVSS
0.1 F
SDATA SL
DVDD2 VRB
NC STBY
48 47 46 45 44 43 42 41 40 39 38 37
NC NC (LSB) D0 D1 D2 D3
VRT CML
SCK
1 2 3 4 5 6 PIN 1 IDENTIFIER
36 35 34 33 32
AUX1IN AVSS AUX2IN AVDD2 BYP4 NC CCDIN BYP2 BYP1
0.1 F 0.1 F 3V ANALOG SUPPLY
AD9841A
TOP VIEW (Not to Scale)
D4 7 D5
8
31 30 29 28 27
CCD SIGNAL 0.1 F 0.1 F 0.1 F 0.1 F
D6 9 D7
10
D8 11 (MSB) D9
12 13 14 15 16 17 18 19 20 21 22 23 24
AVDD1 AVSS 26 AVSS
25
3V ANALOG SUPPLY
DRVDD
DATACLK DVDD1
HD PBLK CLPOB SHP SHD
CLPDM VD
DRVSS DVSS
DATA OUTPUTS
10
3V DRIVER SUPPLY
NC = NO CONNECT
0.1 F 8 CLOCK INPUTS
0.1 F 3V ANALOG SUPPLY
Figure 33. AD9841A Recommended Circuit Configuration for CCD-Mode
REV. 0
-21-
AD9841A/AD9842A
3V ANALOG SUPPLY 0.1 F 1.0 F SERIAL INTERFACE 3 1.0 F
NC THREE-STATE DVSS
0.1 F
SDATA
DVDD2 VRB
NC STBY
48 47 46 45 44 43 42 41 40 39 38 37
D0 1 D1 2 D2 3 D3
4 5
VRT CML
SCK
SL
PIN 1 IDENTIFIER
36 35 34 33
AUX1IN AVSS AUX2IN AVDD2 BYP4 NC CCDIN BYP2 BYP1 AVDD1 AVSS AVSS 0.1 F 0.1 F 3V ANALOG SUPPLY 0.1 F 0.1 F CCD SIGNAL 0.1 F 0.1 F 3V ANALOG SUPPLY
D4
D5 6 D6 D7 D8 D9 D10 (MSB) D11 DATA OUTPUTS 12
8 9
AD9842A
TOP VIEW (Not to Scale)
32 31 30 29 28 27 26 25
7
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24
HD PBLK CLPOB SHP SHD
DRVDD
DATACLK DVDD1
CLPDM VD
DRVSS
DVSS
3V DRIVER SUPPLY
NC = NO CONNECT
0.1 F 8 CLOCK INPUTS
0.1 F 3V ANALOG SUPPLY
Figure 34. AD9842A Recommended Circuit Configuration for CCD-Mode
Internal Power-On Reset Circuitry
After power-on, the AD9842A will automatically reset all internal registers and perform internal calibration procedures. This takes approximately 1 ms to complete. During this time, normal clock signals and serial write operations may occur. However, serial register writes will be ignored until the internal reset operation is completed. Pin 43 (formerly RSTB on the AD9842A non-A) is no longer used for the reset operation. Toggling Pin 43 in the AD9842A will have no effect.
Grounding and Decoupling Recommendations
As shown in Figures 33 and 34, a single ground plane is recommended for the AD9841A/AD9842A. This ground plane should be as continuous as possible, particularly around Pins 25 through 39. This will ensure that all analog decoupling capacitors provide
the lowest possible impedance path between the power and bypass pins and their respective ground pins. All decoupling capacitors should be located as close as possible to the package pins. A single clean power supply is recommended for the AD9841A/AD9842A, but a separate digital driver supply may be used for DRVDD (Pin 13). DRVDD should always be decoupled to DRVSS (Pin 14), which should be connected to the analog ground plane. Advantages of using a separate digital driver supply include using a lower voltage (2.7 V) to match levels with a 2.7 V ASIC, reducing digital power dissipation, and reducing potential noise coupling. If the digital outputs (Pins 3-12) must drive a load larger than 20 pF, buffering is recommended to reduce digital code transition noise. Alternatively, placing series resistors close to the digital output pins may also help reduce noise.
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REV. 0
AD9841A/AD9842A
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
48-Lead LQFP (ST-48)
0.063 (1.60) MAX 0.030 (0.75) 0.018 (0.45)
1
0.354 (9.00) BSC SQ
48 37 36
TOP VIEW
(PINS DOWN)
0.276 (7.00) BSC SQ
25
COPLANARITY 0.003 (0.08) 0.008 (0.2) 0.004 (0.09)
0 MIN
12 13 24
0.019 (0.5) BSC 7 0
0.011 (0.27) 0.006 (0.17) 0.057 (1.45) 0.053 (1.35)
0.006 (0.15) SEATING 0.002 (0.05) PLANE
REV. 0
-23-
PRINTED IN U.S.A.
C02384-2.5-1/01 (rev. 0)

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