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4 & 6 CHANNEL CHARGE PUMPS FOR WHITE LED BIAS
FSP3302/FSP3303
FEATURES
Two LED Configurations Available: FSP3302: Up to 4 LEDs FSP3303: Up to 6 LEDs High Efficiency Proprietary Charge Pump Automatic 1x/1.5x Mode-Switching Ensures Maximum Efficiency Wide 2.7V to 5.2V Input Voltage Range 0.3% White LED Brightness Matching Digitally Programmed 1dB Brightness Steps Up to 44mA per LED Automatic Programming Finish Detection 1.2MHz Operation for Low Ripple Simple Serial Interface Thermal Shutdown Protection Tiny QFN16L and QFN16L Packages
GENERAL DESCRIPTION
The FSP3302/FSP3303 are high performance, white LED bias generators for systems consisting of multiple white LEDs. The FSP3302/FSP3303 are identical except for the number of LEDs they drive; FSP3302 supports up to four LEDs, while FSP3303 can supply up to six LEDs. These devices integrate proprietary constant-frequency charge pump circuitry that includes automatic mode-switching to maximize efficiency with accurate, matched current sources that drive the white LEDs. Current matching is better than 0.3%, resulting in highly uniform brightness across different LED channels. The FSP3302/FSP3303 feature adjustable LED bias currents, which are programmable through a simple serial interface. Charge pump operation at 1.2MHz allows the use of small capacitors and minimizes ripple. The devices also feature soft-start circuitry to limit inrush current during startup, and thermal shutdown protection. The FSP3302/FSP3303 are available in space saving QFN16L and QFN16L packages.
APPLICATIONS
Cell Phones Portable Devices
PIN CONFIGURATION
(Top View)
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FSP3302/FSP3303
PIN DESCRIPTION
Pin Number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 Pin Name D2 D3 D4 (D5) (D6) C1P C1N N/C OUT C2P C2N G N/C IN EN/PROG D1 LED Output 2 LED Output 3 LED Output 4 LED Output 5 (FSP3303 only) LED Output 6 (FSP3303 only) Flying Capacitor 1 Positive Terminal Flying Capacitor 1 Negative Terminal Not Connected Charge Pump Output. Bypass to G with a 1F ceramic capacitor. Flying Capacitor 2 Positive Terminal Flying Capacitor 2 Negative Terminal Ground Not Connected Input Supply. Bypass to G with a 1F ceramic capacitor. IC Enable and Current Programming Pin LED Output 1 Pin Description
ABSOLUTE MAXIMUM RATINGS(NOTE )
Parameter IN Supply, OUT, EN/PROG to G D1, D2, D3, D4, D5, D6, C1P, C1N, C2P, C2N to G C1N, C2N Voltage D1, D2, D3, D4, (D5), (D6) Current Junction to Ambient Thermal Resistance (JA) Operating Junction Temperature Storage Temperature Lead Temperature (Soldering, 10 sec) periods may affect device reliability. QFN16L QFN16L Value -0.3 to 6 -0.3 to VOUT + 0.3 -0.3 to VOUT + 1 58 66 66 -40 to 150 -55 to 150 300 Unit V V V mA C/W C C C
Note : Exceeding these limits may damage the device. Exposure to absolute maximum rating conditions for long
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ELECTRICAL CHARACTERISTICS
(Circuit of the below Figure 1, VIN = 3.5V, TA = 25C unless otherwise specified.) Parameter Input Supply Range Supply Current Shutdown Supply Current Full Scale Output Current Output Current Matching Output Current Line Regulation Charge Pump Switching Frequency Soft-Start Time Thermal Shutdown Temperature EN/PROG Logic Low Threshold Logic High Threshold Programming Low Time Programming Low Time to Reinitialize DAC after Finish Programming Minimum High Time Programming High Time Finish High Time Off Timeout Input Current VIL VIH tLOW tLOW1 tHIGHMIN tHIGH tFINISH tOFF 500 300 500 1 1.4 0.3 5 50 75 75 75 0.5 V V s s ns s s s A fQP tSS Hysteresis = 20C 1000 IDMAX VIN = 3V to 5.5V, 4 LED channels active Between any two channels 38 44 0.3 0.4 1200 330 160 1700 Symbol VIN IQ Test Conditions Min. 2.7 Typ. Max. 5.2 3.5 1 49 Unit V mA A mA % %/V kHz s C
TYPICAL APPLICATION CIRCUIT
Figure 1
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FUNCTIONAL BLOCK DIAGRAM
C1P C1N 1x /1.5x CHARGE PUMP C2P C2N
IN REFERENCE THERMAL SHUTDOWN
OUT
D1
DISCHARGE
OSCILLATOR
CHARGE
CHARGE
D 2 MATCHED CURRENT SOURCES D3 D4 D5 D6
FEEDBACK
EN/ PROG
INTERFACE CONTROL
32-LEVEL LOGARITHMIC DAC
G
FUNCTIONAL DESCRIPTION As shown in the Functional Block Diagram, the FSP3302/FSP3303 incorporate proprietary charge pump technology that includes automatic 1x/1.5x mode-switching to maximize efficiency. Accurate matched current sources are controlled by a 32-level logarithmic DAC in order to provide an accurate, efficient, and programmable bias supply for white LEDs. CHARGE PUMP The FSP3302/FSP3303 charge pump operates at 1.2MHz, and alternately charges and discharges the flying capacitors at C1P, C1N, C2P and C2N to generate sufficient output voltage at OUT to allow accurate biasing of white LEDs. These devices feature an automatic 1x/1.5x mode-switching charge pump architecture to ensure the highest possible efficiency for a charge pump solution. These devices utilize a proprietary regulation technique that minimizes the output impedance of the charge pump, allowing operation that is superior to competing products down to lower input voltages. EN/PROG PIN EN/PROG is a multi-function pin, providing both an enable/disable function as well as permitting the user a simple means to digitally program the LED current ENABLE/DISABLE If EN/PROG is driven low for more than 500s (tOFF), a DISABLE condition is detected and the IC is disabled. Conversely, if EN/PROG remains high for more than 500s (tFINISH), an ENABLE condition is detected, and the DAC is initialized to -31dB upon the next high to low transition of EN/PROG. To properly reset the DAC upon enabling the IC, the input voltage should be applied first while EN/PROG is driven low. A subsequent low to high transition on EN/PROG pin turns the IC on. PROGRAMMING LED CURRENT The interface control block decodes the digital serial input signal at EN/PROG and produces a programming code for the 32-level logarithmic DAC. The logarithmic DAC sets the output currents to one of 32 different levels, in 1dB steps, with the highest level of 0dB corresponding to the full-scale current of 44mA. Logarithmic current scaling results in linear increments in LED brightness. When enabled (on an EN/PROG rising edge), the DAC initializes to its -31dB level. Thereafter, each high to low transition of the EN/PROG pin that occurs within 75s increments the
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FSP3302/FSP3303
DAC, and therefore the LED current, by 1dB. Once the maximum current level of 0dB is reached, an additional high to low transition on EN/PROG resets the DAC level to its minimum value of -31dB. Figure 2 demonstrates the EN/PROG serial protocol.
tHIGH tLOW tOFF
OFF
31dB
30dB
29dB
OFF
t > tFINISH
tLOW1
31dB
30dB
29dB
28dB
Figure2. EN/PROG Serial Protocol To ensure proper DAC initialization, the first low pulse after programming is completed should be at least 5s. SOFT START When enabled, the FSP3302/FSP3303 operate in a low power state for 330s (tSS) to limit inrush current. After this time has expired, the devices operate in full-power mode. THERMAL SHUTDOWN
In order to protect themselves under thermal overload and short circuit conditions, the FSP3302/FSP3303 incorporate thermal shutdown circuitry that monitors the die temperature and disables the IC if it exceeds 160C.
TYPICAL PERFORMANCE CHARACTERISTICS
(Circuit of Figure 1, VIN = 3.5V, TA = 25C unless otherwise specified.)
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TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
(Circuit of Figure 1, VIN = 3.5V, TA = 25C unless otherwise specified.)
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TYPICAL PERFORMANCE CHARACTERISTICS (CONTINUED)
(Circuit of Figure 1, VIN = 3.5V, TA = 25C unless otherwise specified.)
APPLICATION INFORMATION
CAPACITOR SELECTION For best performance, use only ceramic capacitors, as they offer small size, low ESR, low cost, and high reliability. Since the dropout resistance is dependent on the ESR of the capacitors, lower ESR also allows the circuit to supply the required output currents at lower input voltage. X7R and X5R ceramic types are most stable (15%) over bias voltage and temperature ranges and thus are highly recommended. Lower cost Y5V and Z5U ceramic types vary widely with voltage and temperature, and they should only be used after careful verification of the effects the capacitance degradation has on the application. Choose values for the flying capacitors of at least 1F. For best results choose input and output capacitors of at least 1F. WHITE LED SELECTION The FSP3302/FSP3303 are designed to bias multiple parallel white LEDs. The LED currents are internally matched and change very little with each LED's forward voltage. For best operation, ensure that the maximum LED forward voltage is 4.2V. The FSP3302/FSP3303 utilizes a proprietary design that results in significantly better dropout performance than competing products. Whereas other products maintain constant current for input voltages down to 3.0V, the FSP3302/FSP3303 are capable of providing constant output current for input voltages extending down to as low as 2.7V. EFFICIENCY The FSP3302/FSP3303 automatically adjust their operating mode to ensure the highest possible efficiency for a given set of operating conditions. The theoretical maximum efficiency of a charge pump is a function of its operating mode, and is given by MAX = VLED / KVIN where K is equal to 1 for a 1x operating mode and 1.5 for a 1.5x operating mode. Compared to this theoretical maximum efficiency, the FSP3302/FSP3303 achieve efficiency that is within just 2% of the theoretical maximum for full scale output currents. This ensures the lowest possible battery current and the maximum possible battery life in portable applications.
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ORDERING INFORMATION
FSP3302/FSP3303XXX Package: Q: QFN16L Q: QFN 16L Packing: A: Tape & Reel Temperature Grade: D: -40~85
MARKING INFORMATION
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PACKAGE INFORMATION
(1) QFN16L
Symbol A A1 A2 D E D1 E1 b e L K
Dimensions In Millimeters Min. 0.700 0.000 0.200 REF 2.900 2.900 1.500 1.500 0.180 0.500 BSC 0.350 0.200 0.450 0.400 3.100 3.100 1.700 1.700 0.280 Max. 0.800 0.050
Dimensions In Inches Min. 0.028 0.000 0.008 REF 0.114 0.114 0.059 0.059 0.007 0.020 BSC 0.014 0.008 0.018 0.016 0.122 0.122 0.067 0.067 0.011 Max. 0.031 0.002
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(2) QFN16L
Symbol A A1 D E D1 E1 b e L L1
Dimensions In Millimeters Min. 0.010 2.900 2.900 1.700 1.700 0.150 0.500 BSC 0.350 0.000 0.450 0.050 0.250 Max. 0.900 0.090 3.100 3.100
Dimensions In Inches Min. 0.0004 0.114 0.114 0.067 0.067 0.006 0.020 BSC 0.014 0.000 0.018 0.002 0.010 Max. 0.035 0.0035 0.122 0.122
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