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CAT4106 6W Quad Channel DC/DC LED Driver with Diagnostics
FEATURES
Four LED Channels with tight current matching Integrated DC/DC Boost converter Up to 6 W LED Total Output Power Up to 92% Efficiency Low Dropout LED Channels (500 mV at 175 mA) High Frequency PWM interface (up to 2 kHz) Adjustable Short/Open LED Detection Programmable LED Channel current Adjustable LED Channel voltage Thermal shutdown protection RoHS-compliant 16-lead TQFN 4 x 4 mm and TSSOP packages
DESCRIPTION
The CAT4106 is an integrated multi-channel LED driver and high power DC/DC converter suitable for powering backlighting applications up to a total of 6 watts. Up to four matched LED strings can be accurately programmed with uniform drive current set by a single external resistor. Each output channel is suitable for LED string voltages of up to 36 V. The driver automatically adjusts the output voltage to drive the highest forward voltage string with the minimum headroom voltage maximizing the efficiency. High resolution dimming control is achieved by the EN/PWM logic pin which supports multiple frequencies. This ensures precise PWM dimming control while the device remains fully biased. In addition, when held at logic low, the device to enter a full shutdown "zero" current mode. External programming resistors set the minimum and maximum voltage limits for the acceptable "window of operation" for LED strings. Any channel which fails to regulate within the window (Open or Short LED) is detected and flagged on the FAULT logic output (active low, open-drain). The device is available in a 16-lead TQFN 4 mm x 4 mm and TSSOP with exposed pad packages. For Ordering Information details, see page 16.
LED2 LED3 LED4 RSET VFMAX VFMIN CTRL VIN
APPLICATIONS
LCD Backlight Lighting Automotive and General Purpose Lighting
ORDERING INFORMATION
Part Number CAT4106YP-T2
Notes: (1) (2)
Package TSSOP-16 (2)
Quantity per Reel 2,000 2,000
Package Marking CDAL 4106Y
CAT4106HV4-GT2 TQFN-16 (1)
NiPdAu Plated Finish (RoHS-compliant) Matte-Tin Plated Finish (RoHS-compliant).
PIN CONFIGURATION
TSSOP 16-Lead (Top View)
LED1 GND FAULT PGND FB SW EN/PWM NC
1 2 3 4 5 6 7 8 16 15 14 13 12 11 10 9
TYPICAL APPLICATION CIRCUIT
VL 3 V to 24 V C2 L 47 H D C3 10 F/50 V VIN SW VFMAX VFMIN R4 R6
TAB is GND
4.7F VIN 3 V to 5.5 V C1
TQFN 16-Lead (Top View)
RSET
1 F OFF... ON... DIM EN/PWM RSET R2 20 k CTRL R3 R1 20 k FB
CAT4106
LED1 LED2 LED3 LED4 PGND FAULT
R5
R7
16 LED1 GND FAULT PGND 1 2 3 4 5
FB
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
LED2
15
LED3
14
TAB is GND
LED4
13 12 VFMAX 11 VFMIN 10 CTRL 9 VIN
VIN R8 LED Fault Detection (open drain pull-down)
GND
6
SW
7
EN/PW
8
NC
1
Doc. No. MD-5037, Rev. A
CAT4106
ABSOLUTE MAXIMUM RATINGS (1)
Parameters VIN, RSET, EN/PWM, CTRL, FB, FAULT VFMIN, VFMAX LED1, LED2, LED3, LED4 SW (internally clamped to 40 V) Storage Temperature Range Junction Temperature Range Lead Temperature Ratings -0.3V to 6 -0.3V to 6 -0.3V to 25 50 -65 to +160 -40 to +150 300 Units V V V V C C C
RECOMMENDED OPERATING CONDITIONS
Parameter VIN Inductor Drive Voltage LED String Forward Voltage per channel Ambient Temperature Range ILED per LED pin Typical application circuit with external components is shown on page 1. Range 3.0 to 5.5 3.0 to 24 up to 36 -40 to +85 10 to 175 Units V V V C mA
RECOMMENDED EN/PWM TIMING
Symbol TLEDSETUP TLO THI TPWRDWN TLEDSET Name
For 3.0 VIN 5.5V, over full ambient temperature range -40 to +85C. Conditions Min 10 0.2 0.2 8 ILED = 100 mA 0.2 Typ 40 Max 100 2000 Units s s s ms s LED setup time from shutdown EN/PWM low time EN/PWM high time EN/PWM low time to shutdown delay LED current settling time
TLEDSETUP EN/PWM SHUTDOWN 100% BRIGHTNESS
THI
TLO
TPWRDWN
DIMMING
POWERDOWN
SHUTDOWN
LED CURRENT
DEVICE QUIESCENT CURRENT
Figure 3. CAT4106 EN/PWM Timing
Notes: (1) Stresses above those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions outside of those listed in the operational sections of this specification is not implied. Exposure to any absolute maximum rating for extended periods may affect device performance and reliability.
Doc. No. MD-5037, Rev. A
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(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
ELECTRICAL OPERATING CHARACTERISTICS
VIN = 5 V, VL (inductor drive voltage) = 12 V, TAMB = 25C (over recommended operating conditions unless specified otherwise) Symbol IQ ISD VIH VIL REN VUVLO TSD THYS VRSET ILED/IRSET VDO ILED ILED-OFF VVFMAX VVFMIN VCTRL ICTRL I FAULT VFB IFB FSW Description VIN Operating Current VIN input shutdown Current EN/PWM Logic High Threshold Logic Low Threshold Internal Pull-Down Resistor Undervoltage lockout (UVLO) Thermal Shutdown Threshold Thermal Hysteresis RSET regulation voltage RSET to LED Current gain ratio LED Channel Dropout Voltage LED Channel Matching LED Channel leakage O/C Detect voltage threshold S/C Detect voltage threshold CTRL pin voltage accuracy CTRL pin maximum load Pull-down Drive Current Open Drain Leakage Current FB Pin control voltage FB pin input leakage current SW Pin Switching Frequency Switch Pin Current Limit Switch Pin On-resistance Maximum Duty Cycle Minimum Duty Cycle Switch Leakage Current Over Voltage Protection Detect Offset to Lowest LED output is Active (0.1 V bias) FAULT is Inactive FAULT Normal switching mode regulation 10 A < IRSET < 2 mA. 30 mA LED current ILED = 175 mA 0.5 V < VLED < 5 V Channel is Off 1.15 1.15 - 0.1 25 1 285 1.20 1.20 0 2 1 300 315 1 1.3 -5 1.17 Conditions Switching Not Switching Switching Not Switching VEN = 0V Min (ILED = 30 mA) (ILED = 30 mA) (ILED = 60 mA) (ILED = 60 mA) Typ 2.5 2.0 3.4 2.9 Max 3.5 3.0 4.4 3.9 1 1.3 300 Units mA A V V k V C C 1.23 V V +5 1 1.25 1.25 + 0.1 % A V V V A mA A mV A MHz A % % A V
Device Enable Level Disable/PWM Level VIN pin voltage
0.4 100
0.8 0.7 200 2.0 150 20 1.20 100 0.5 1
ISWMAX RSW DCMAX DCMIN ISWLEAK OVPSW
0.7 0.8 ISW = 500 mA Prior to Current Limiting Prior to Pulse-Skipping VSW = 20 V Enters Low Power mode
1.0 1.0 1.0 96 5 40
5
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
3
Doc. No. MD-5037, Rev. A
CAT4106
TYPICAL ELECTRICAL OPERATING CHARACTERISTICS
VIN = 5 V, VL = 12 V, TAMB = 25C, typical application circuit unless otherwise specified. Quiescent Current vs. RSET Current
8 QUIESCENT CURRENT [mA]
RSET Voltage vs. VIN Supply
1.30
switching
4 not switching 2
RSET VOLTAGE [V]
6
1.25
1.20
1.15
0 0.0 0.5 1.0 1.5 2.0 RSET CURRENT [mA]
1.10 3.0 3.5 4.0 4.5 5.0 5.5 VIN SUPPLY [V]
RSET Voltage vs. Temperature
1.30
ILED/IRSET Gain vs. LED Current
140
RSET VOLTAGE [V]
1.25
120
GAIN
1.20
100
1.15
80
1.10 -50 0 50 100 150 TEMPERATURE [C]
60 20 60 100 140 180 LED CURRENT [mA]
LED Channel Current vs. LED Pin Voltage
200 175 LED CURRENT [mA]
LED Channel Current vs. VIN Supply
200 175 LED CURRENT [mA] 150 125 100 75 50 25 0 3.0 3.5 4.0 4.5 5.0 5.5
150 125 100 75 50 25 0 0.0 0.2 0.4 0.6 0.8 1.0 LED PIN VOLTAGE [V]
VIN SUPPLY [V]
Doc. No. MD-5037, Rev. A
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(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
TYPICAL ELECTRICAL OPERATING CHARACTERISTICS
VIN = 5 V, VL = 12 V, TAMB = 25C, typical application circuit unless otherwise specified. LED Channel Voltage vs. VIN Supply
0.9
FAULT DRIVE RDSON []
FAULT Drive RDSON vs. VIN Supply
30 25 20 15 10 5
LED PIN VOLTAGE [V]
0.8 0.7 0.6 0.5 R2 = R3 = 24k 0.4 3.0 3.5 4.0 4.5 5.0 5.5 VIN SUPPLY [V]
3.0
3.5
4.0
4.5
5.0
5.5
VIN SUPPLY [V]
Switch Resistance vs. VIN Supply
2.0
Switching Frequency vs. VIN Supply
1.2 SWITCHING FREQUENCY [MHz]
SWITCH RESISTANCE []
1.5
1.1
1.0
1.0
0.5
0.9
0.0 3.0 3.5 4.0 4.5 5.0 5.5 VIN SUPPLY [V]
0.8 3.0 3.5 4.0 4.5 5.0 5.5 VIN SUPPLY [V]
Switching Current Limit vs. VIN Supply
1200
Powerdown Delay vs. VIN Supply
5 POWERDOWN DELAY [ms] 4 3 2 1 0 3.0 3.5 4.0 4.5 5.0 5.5 VIN SUPPLY [V]
SW CURRENT LIMIT [mA]
1100 1000 900 800 700 600 3.0 3.5 4.0 4.5 5.0 5.5 VIN SUPPLY[V]
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
5
Doc. No. MD-5037, Rev. A
CAT4106
TYPICAL ELECTRICAL OPERATING CHARACTERISTICS
VIN = 5 V, VL = 12 V, TAMB = 25C, typical application circuit unless otherwise specified. EN/PWM Threshold vs. VIN Supply
1.00 EN/PWM THRESHOLD [V]
TOTAL LED CURRENT [%]
PWM Duty Cycle vs. LED Current
100
0.95 0.90 0.85 0.80 0.75 0.70 3.0 3.5 4.0 4.5 5.0 5.5 VIN SUPPLY [V] VHI
VLO
100Hz 10 1kHz
1 1 10 DUTY CYCLE [%] 100
PWM Dimming 100 Hz
PWM Dimming 1 kHz
Power-Up 4 x 10 LEDs, 50 mA per Channel
MAX ILED PER CHANNEL [mA]
Maximum LED Current vs. VL Supply
200 VOUT = 20V 150 25V 100
50 30V 0 2 4 6 8 10 12 14 16 VL [V]
Doc. No. MD-5037, Rev. A
6
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
TYPICAL ELECTRICAL OPERATING CHARACTERISTICS
VIN = 5 V, VL = 12 V, 20mA per channel (80mA total output current), TAMB = 25C, typical application circuit unless otherwise specified. Efficiency vs. VIN (VIN = VL)
100 95 EFFICIENCY [%]
EFFICIENCY [%] 100 95 90 85 80 VOUT = 24V 75 70
Efficiency vs. VL (VIN = 5V)
90 85 80 75 70 4.5 4.7 4.9 5.1 5.3 5.5 INPUT VOLTAGE [V] VOUT = 19V
8
10
12
14
16
INDUCTOR VOLTAGE [V]
Efficiency vs. Output Current (9-LED string)
100 95 EFFICIENCY [%] 90 85 80 75 70 40 80 120 160 200 240 OUTPUT CURRENT [mA]
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7
Doc. No. MD-5037, Rev. A
CAT4106
PIN DESCRIPTION
Name LED1 GND FAULT PGND FB SW EN/PWM N.C VIN CTRL VFMIN VFMAX RSET LED3 LED3 LED4 TAB TQFN-16 TSSOP-16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 TAB Function LED1 cathode terminal Signal Ground reference Open/Short LED Fault detection output (active-low) Power Ground Reference (DC/DC Power Switch) Feedback reference (300 mV) for setting LED channel operating voltage Internal power FET switch drain connection Device Enable (active high) and PWM control input Not connected Supply voltage for the device LED channel operating voltage (lowest of all 4 channels) Comparator input for setting the LED string short-circuit voltage limit Comparator input for setting the LED string open-circuit voltage limit RSET resistor pin for setting the LED channel operating current LED3 cathode terminal LED3 cathode terminal LED4 cathode terminal Thermal pad (connect to GND and PGND)
PIN DESCRIPTIONS
VIN is the supply pin for the device. The supply input current needed for normal operation is approximately 2 mA plus 3 times IRSET pin current. During intervals of PWM dimming, or whenever the converter is not switching, the supply current will decrease by around 1 mA. The voltage applied at VIN should be kept between 3 V and 5.5 V. A small ceramic bypass capacitor of 0.1 F or greater is recommended to be in close proximity to the VIN pin. EN/PWM is the device Enable and PWM dimming control input for all LED channels. Guaranteed levels of logic high and logic low are set at 1.3 V and 0.4 V respectively. During normal PWM dimming, the entire device remains fully biased and only the LED channels are pulsed on/off. The device will only enter zero current shutdown mode after the EN/PWM is help low for at least 5 ms typically. This pin has an internal pull-down resistor of 200 k. RSET is the voltage regulated control pin for sensing the desired programming current level to be applied on all LED channels. During normal operation, the RSET pin is kept at 1.2 V and accurately monitors the current level in the externally applied R1 resistor. The current transfer ratio from RSET pin current to LED pin current is 100.
Doc. No. MD-5037, Rev. A
LED1 to LED4 provide the regulated current source for driving each of the LED strings with a tightly matched constant current. To ensure optimal performance, the bias voltage on the LED channels should be set at a nominal 0.6 V or higher. Each channel is capable of driving a current up to 175 mA. All channels immediately enter a high impedance mode whenever the EN/PWM is taken LOW. CTRL pin is a multiplexer output which selects the lowest operating voltage appearing on any of the four LED output drive channels. This control signal represents the cathode terminal voltage of the LED string with greatest forward voltage (VF). An external resistor network from CTRL to FB can be used to set the lowest operating voltage of each channel. External current loading of the CTRL pin is recommended to be less than 25 A. FB is the voltage feedback control pin for the internal high power DC/DC converter. This pin has a high impedance input and its voltage remains accurately regulated to 0.3 V during normal steady state operation
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(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
SW pin is the drain terminal of the high voltage CMOS power switch which has a typical on-resistance of 1 and is current limited to 1 A typically. An overvoltage protection circuit places the device in a soft-clamping low power mode if the voltage transients exceed 40 V. VFMIN pin uses a pair of external resistors (R6 & R7) to program the worst case, minimum LED string forward voltage (VFMIN) expected in the specific application. If, during power-up, any LED string enters full regulation before this programmed level is reached (VFMIN pin voltage < 1.2 V), the string will be considered to contain LEDs which are short-circuit and a fault condition will be flagged. The VFMIN input circuitry consists of a comparator referenced to 1.2 V. A typical value for resistor R7 is around 20 k. R6 can be calculated as follows:
VFMAX programmed voltage. The VFMAX input circuitry consists of a comparator referenced to 1.2 V. A typical value for resistor R5 is 20 k. R4 can be calculated as follows:
V R4 = R5 x FMAX - 1 1 .2 V
If this detection feature is not needed, the VFMAX pin must be tied to ground.
is an open-drain, active-low, logic signal which FAULT becomes active during an LED short-circuit or opencircuit condition. The pin must be connected to a pullup resistor of around 100 k tied to VIN. The drive pull-down resistance (when active) is typically less than 100 . The diagnostic sequence used to determine a fault condition is initiated when the device is first enabled. PGND pin is the source connection terminal of the high voltage CMOS power switch in the DC/DC converter. The inductor supply bypass capacitor should be connected in close proximity to the PGND pin. The return current from PGND should be connected to the PCB ground plane. GND is the ground reference pin for the device. All analog control voltages are referenced to this pin. In addition, all LED drive currents are conducted through the GND pin. TAB is the thermal pad connection of the package and should be connected to PCB ground plane.
V R6 = R7 x FMIN - 1 1 .2 V If this detection feature is not needed, the VFMIN pin must be tied to ground.
VFMAX pin uses a pair of external resistors (R4 & R5) to program the worst case, maximum LED string forward voltage (VFMAX) expected in the specific application. If any LED string fails to become regulated before the programmed voltage is reached, the string will be considered to contain LEDs which are open-circuit and a fault condition will be flagged. When an open-circuit is flagged, the individual channel that causes the open-circuit is internally flagged and subsequently ignored. In the event that all channels are detected as being Open-LED, the Output Voltage (top LED Anode) will stabilize at the
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
9
Doc. No. MD-5037, Rev. A
CAT4106
BLOCK DIAGRAM
VL L D C3 R4 R5 R6 R7
SW OVP Controller 1MHz PWM Controller
1A 1
VFMAX
VFMIN FAULT Ctrl/Fault Detector CTRL
LED Cluster N_Series M_Parallel
C Diagnostics
LEDn
300mV
R2
FB VIN Supply System EN/SD I1 PWM_DIM
200 k
LED1
LED1 LED2 LED3 LED4 I2 I3 I4 0 - 175 mA
EN/DIM
Shutdown Delay
Drive Control IRSETx100
R3
RSET
R1
GND
PGND
Figure 4. CAT4106 Simplified Functional Block Diagram
DEVICE OPERATION
In a typical application, the CAT4106 drives an LED array consisting of up to four separate strings. A single external resistor value is used to select the drive level in all output channels. Each channel provides a very well regulated and tightly matched bias current on all LED strings. An integrated DC/DC boost converter is used to generate the high voltage output required to power the LED strings. Up to a maximum of 6 W of LED power can be delivered when powered from a 12 V supply. To offer improved performance, the device also allows the user to set the operating voltage level on the output drive channels. A pair of external resistors is used to control the nominal channel voltage, during normal operation. The resulting output voltage (LED anodes) will be equal to the sum of the adjusted channel voltage plus the maximum forward voltage present on any string. The CAT4106 provides four tightly matched current sinks to accurately regulate LED current in each channel. Up to 175 mA per channel can be programmed by selecting a suitable value for the
Doc. No. MD-5037, Rev. A
external R1 resistor (connected between RSET and GND pins).
LED CURRENT SETTING The CAT4106 provides four tightly matched current sinks to accurately regulate LED current in each channel. The LED current is set by the external resistor R1 connected between the feedback pin (FB) and ground. The following formula gives the relationship between the resistor value and the LED current per channel. 1 .2 V R1 103 x LED current per channel LED current per channel (mA) 10 20 30 50 100 150 R1 () 12.4 k 6.19 k 4.12 k 2.49 k 1.24 k 820
Table 1. Resistor R1 and LED current
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(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
SETTING THE CHANNEL VOLTAGE Each LED channel typically requires less than 0.5 V of headroom for full load operation. The lowest channel operating voltage can be controlled and programmed via the external resistor network connected between, CTRL, FB and GND as shown in Figure 4.
Lowest LED pin voltage = VFB x R2 + R3 R3
The test condition in Figure 5 is with one LED pin shorted to the output (top LED anode). The test condition in Figure 6 is with one LED pin floating or disconnected. In both cases, the CAT4106 is set to drive 50 mA per channel.
SETTING VFMIN LEVEL (SHORT-LED) The VFMIN level represents the minimum level expected for the LED string voltage "window of operation". This voltage setting is based on the number of series LEDs being used and the expected minimum forward voltage VF during normal operation.
For most applications, a gain of 2x (R2 equals R3) is recommended. The CTRL output pin has optimal performance when loaded with around 15 A, which equates to an R3 resistor value of 20 k.
LED DETECTION The CAT4106 detects failure conditions related to the LED load, such as if one of the LED strings has been disconnected (Open-LED) or if one LED string has a lower LED pin voltage than expected (Short-LED). Either condition is flagged by turning on the opendrain output on the FAULT pin. The Open-LED detection is active in normal operation. The Short-LED detection is only active during power-up, just after the EN/PWM input goes from low to high. If in normal operation (LEDs are in regulation) a short-LED condition occurs, it will not be detected.
Example: Consider a string of 6 LEDs in series, with each LED having a VF range of 3.5 V 0.5 V. Since the minimum VF of each LED is 3.0 V the overall lowest expected string voltage would be 18 V. Any string voltage of less than 18 V is considered as a short-circuit fault in one or more of the series LEDs. The external resistor R6 value needed to set a VFMIN level of 18 V is calculated as follows:
18 V R6 = R7 x 1.2 V - 1
For R7 = 20 k, R6 = 280 k.
SETTING VFMAX LEVEL (OPEN-LED) The VFMAX level represents the maximum level expected for the LED string voltage "window of operation". This voltage setting is based on the number of series LEDs being used and the expected maximum VF during normal operation.
Figure 5. Cold Power-Up Short-LED Detection
Example: Consider a string of 6 LEDs in series, with each LED having a VF range of 3.5 V 0.5 V. Since the maximum VF of each LED is 4.0 V, the overall maximum expected string voltage would be 24 V. Any string voltage which appears greater than 24 V would be considered as containing an open-circuit in one or more of the series LEDs. The external resistor R4 value needed to set a VFMAX level of 24 V is calculated as follows:
24 V R4 = R5 x 1.2 V - 1
For R5 = 20 k, R4 = 380 k. In normal operation, the LED string which has the largest VF will be used to set the VCTRL/VFB voltage levels. If the largest string voltage tries to exceed VFMAX setting, it will no longer be allowed to control the voltage level of VCTRL/VFB (i.e it will be ignored) and subsequently the next largest LED string voltage will then be used in the control loop. All remaining functional LED channels will continue to operate as
Figure 6. Normal Operation Open-LED Detection
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
11
Doc. No. MD-5037, Rev. A
CAT4106
normal. If a disconnected LED string is reconnected, the FAULT flag remains on and the channel disabled until the device has been re-enabled with the EN pin going from low to high. If all LED channels are detected as being open-circuit, then the boost converter will limit the output voltage to the VFMAX setting. This eliminates the need for an external protection zener.
ENABLE AND PWM DIMMING CONTROL EN/PWM input signal provides two independent functions. The first function is to enable and disable the entire device. The second function is to apply PWM dimming on the output channels while the chip remains fully enabled. Applying logic high on the EN/PWM input will power up the device. The device will continue to remain powered up, even in the presence of PWM signals being applied. To disable the device into complete system shutdown mode, a logic low must be applied to the EN/PWM input for typically 5 ms. ONE OR TWO LED STRING APPLICATIONS The CAT4106 can be used to drive one or two strings of LEDs by connecting together some LED pins. Also for applications requiring LED current greater than 175 mA, LED channels can be tied together, assuming the supply is suitable to drive the load. Figure 7 shows a typical application for driving a single string of LEDs. The LED current is equal to four times the channel current.
VL C2 VIN C1 L D
C3 R4 VIN SW VFMAX VFMIN R6
CAT4106
OFF... ON... DIM... EN/PWM RSET R2 VCTRL FB R1 R3 GND PGND LED1 LED2 LED3 LED4 FAULT
R5
R7
VIN R8 LED Fault Detection (open drain pull-down)
The duty cycle applied at the EN/PWM is directly applied to all the output channels. Each time the input is taken low, all output channels will immediately be switched off and the channels will resume normal operation when the PWM is taken back high. The response time of the channels when switching ON or OFF is typically 0.2 s. During PWM dimming, the recommended minimum pulse width interval (either High or Low) is 0.2 s. The recommended maximum pulse width during PWM dimming is 2.5 ms, however this only applies to the Low pulse interval. Pulse durations extending past 2.5 ms may cause the device to enter full shutdown mode. The LED channel response time is much longer if the device has been in shutdown mode. For most applications, a maximum dimming resolution can be achieved with PWM clock frequencies in the range of 100 Hz to 2 kHz. Pulse width intervals of 1 s, allows up to 1000:1 dimming ratio at 1 kHz PWM frequency.
Figure 7. Application Circuit for One LED String
Figure 8 shows a typical application for driving two strings of LEDs. The LED current is equal to two times the channel current.
VL C2 VIN C1 L D
C3 R4 VIN SW VFMAX VFMIN R6
CAT4106
OFF... ON... DIM... EN/PWM RSET R2 VCTRL FB R1 R3 GND PGND LED1 LED2 LED3 LED4 FAULT
R5
R7
VIN R8 LED Fault Detection (open drain pull-down)
Figure 8. Application Circuit for Two LED Strings
Doc. No. MD-5037, Rev. A
12
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
APPLICATION INFORMATION
External Component Selection Capacitors The CAT4106 requires small ceramic capacitors of 1 F on the VIN pin (C1), 4.7 F on the inductor input (C2), and 10 F on the output (C3). Under normal condition, a 4.7 F input capacitor (C2) is sufficient. The voltage rating of each capacitor should be compatible with the maximum voltage applied. For the output, a 50 V rated capacitor (C3) is recommended in case the LED becomes disconnected (Open-LED condition). X5R and X7R capacitor types are ideal due to their stability across temperature range. Inductor A 47 H inductor is recommended for most applications. In cases where the efficiency is critical, inductances with lower series resistance are preferred. Inductors with current rating of 1 A or higher are recommended for most applications. Coilcraft CR73-470 inductor rated at 1.08 A is recommended for most applications. Schottky Diode The current rating of the Schottky diode (D) must exceed the peak current flowing through it. A 1A rated Schottky diode is recommended. The Schottky diode performance is rated in terms of its forward voltage at a given current. In order to achieve the best efficiency, this forward voltage should be as low as possible. The response time is also critical since the driver is operating at 1 MHz. NXP PMEG6010CEJ (60 V / 1 A rated) Schottky barrier rectifier is recommended for most applications. Recommended Layout The board layout should provide good thermal dissipation through the PCB. Multiple via can be used to connect the tab of the CAT4106 to a large ground plane underneath the package.
Input capacitor C1 should be placed as close to the driver IC as possible. The RSET resistor (R1) and channel voltage setting resistor (R3) should have a Kelvin connection to the GND pin of the CAT4106.
Figure 9. Recommended Layout for TQFN-16
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
13
Doc. No. MD-5037, Rev. A
CAT4106
PACKAGE OUTLINE DRAWINGS TQFN 16-Pad 4 x 4 mm (HV4)
(1) (2)
D
A DETAIL A
E
E2
PIN#1 ID D2
PIN#1 INDEX AREA TOP VIEW
A1 SIDE VIEW
BOTTOM VIEW
SYMBOL
MIN
NOM
MAX
b
e
A A1 A3 b D D2 E E2 e L
0.70 0.00 0.25 3.90 2.00 3.90 2.00 0.45
0.75 0.02 0.20 REF 0.30 4.00 - 4.00 - 0.65 BSC -
0.80 0.05 0.35 4.10 2.25 4.10 2.25 0.65
A1 A3 FRONT VIEW A L DETAIL A
For current Tape and Reel information, download the PDF file from: http://www.catsemi.com/documents/tapeandreel.pdf.
Notes: (1) All dimensions are in millimeters. Angles in degrees. (2) Complies with JEDEC standard MO-220
Doc. No. MD-5037, Rev. A
14
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
TSSOP 16-Lead Exposed Thermal Pad 4.4 mm (YP)
b c
(1) (2)
X
E1 E
Y
L1 PIN#1 IDENTIFICATION TOP VIEW D A2 A e 1 END VIEW
L EXPOSED THERMAL PAD ZONE BOTTOM VIEW
X 0.076
SIDE VIEW
A1
SYMBOL
MIN
NOM
MAX
A A1 A2 b c D E E1 e L L1 N P R S 1 X Y
0.05 0.85 0.19 0.13 4.90 6.30 4.30 0.65 BSC 1.00 REF 0.45 0.90 6.50 4.60 0.37 0 2.74 REF 2.74 REF
1.10 0.15 0.95 0.30 0.20 5.10 6.50 4.50
Y 0.076 P R
0.75 1.00 6.70 4.80 0.47 8
S LAND PATTERN
e
N
Notes: (1) All dimensions are in millimeters. Angles in degrees. (2) Complies with JEDEC standard MO-153 variations ABT
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
For current Tape and Reel information, download the PDF file from: http://www.catsemi.com/documents/tapeandreel.pdf.
15
Doc. No. MD-5037, Rev. A
CAT4106
EXAMPLE OF ORDERING INFORMATION (1)
Prefix CAT
Company ID
Device # 4106
Product Number
Suffix HV4
Package HV4: TQFN 16-Pad (3) YP: TSSOP 16-Lead Exposed Thermal Pad
-
G
Lead Finish G: NiPdAu Blank: Matte-Tin
T2
Tape & Reel T: Tape & Reel 2: 2,000/Reel
4106
For Product Top Mark Codes, click here: http://www.catsemi.com/techsupport/producttopmark.asp
Notes: (1) All packages are RoHS-compliant (Lead-free, Halogen-free). (2) The standard plated finish is NiPdAu. (3) TSSOP only available in Matte-Tin plated finish. (4) The device used in the above example is a CAT4106HV4-GT2 (TQFN, NiPdAu, Tape & Reel, 2,000/Reel). (5) For additional temperature options, please contact your nearest ON Semiconductor Sales office.
Doc. No. MD-5037, Rev. A
16
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice
CAT4106
REVISION HISTORY
Date 17-Feb-09 Revision A Description Initial Issue
ON Semiconductor and are registered trademarks of Semiconductor Components Industries, LLC (SCILLC). SCILLC reserves the right to make changes without further notice to any products herein. SCILLC makes no warranty, representation or guarantee regarding the suitability of its products for any particular purpose, nor does SCILLC assume any liability arising out of the application or use of any product or circuit, and specifically disclaims any and all liability, including without limitation special, consequential or incidental damages. "Typical" parameters which may be provided in SCILLC data sheets and/or specifications can and do vary in different applications and actual performance may vary over time. All operating parameters, including "Typicals" must be validated for each customer application by customer's technical experts. SCILLC does not convey any license under its patent rights nor the rights of others. SCILLC products are not designed, intended, or authorized for use as components in systems intended for surgical implant into the body, or other applications intended to support or sustain life, or for any other application in which the failure of the SCILLC product could create a situation where personal injury or death may occur. Should Buyer purchase or use SCILLC products for any such unintended or unauthorized application, Buyer shall indemnify and hold SCILLC and its officers, employees, subsidiaries, affiliates, and distributors harmless against all claims, costs, damages, and expenses, and reasonable attorney fees arising out of, directly or indirectly, any claim of personal injury or death associated with such unintended or unauthorized use, even if such claim alleges that SCILLC was negligent regarding the design or manufacture of the part. SCILLC is an Equal Opportunity/Affirmative Action Employer. This literature is subject to all applicable copyright laws and is not for resale in any manner.
PUBLICATION ORDERING INFORMATION
LITERATURE FULFILLMENT: Literature Distribution Center for ON Semiconductor P.O. Box 5163, Denver, Colorado 80217 USA Phone: 303-675-2175 or 800-344-3860 Toll Free USA/Canada Fax: 303-675-2176 or 800-344-3867 Toll Free USA/Canada Email: orderlit@onsemi.com N. American Technical Support: 800-282-9855 Toll Free USA/Canada Europe, Middle East and Africa Technical Support: Phone: 421 33 790 2910 Japan Customer Focus Center: Phone: 81-3-5773-3850 ON Semiconductor Website: www.onsemi.com Order Literature: http://www.onsemi.com/orderlit For additional information, please contact your local Sales Representative
Doc. No. MD-5037 Rev. A
17
(c) 2009 SCILLC. All rights reserved. Characteristics subject to change without notice

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