STP4CMP. Low voltage 4-channel constant current LED driver with charge pump. Description. Features. Applications

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1 Low voltage 4-channel constant current LED driver with charge pump Datasheet - production data Features Operating voltage range: V CC.7 V to 5.5 V Full RGB function support 4-channel LED driver with individual ON/OFF control directly from input pins Individually programmable output current for the 4 channels through 4 external resistors with a max. capability of 30 ma Absolute output current accuracy of max. ±7% and channel-to-channel mismatch of max. ±4% Selectable charge pump enable/disable Thermal protection Small QFN0 (.8x3. mm) package Applications QFN0 (.8x3. mm) Mobile phone display backlighting RGB LED indicator driver Description The is a charge-pump-based 4- channel LED driver designed for RGB illumination or LCD display backlighting. The works off a battery with an input voltage between.7 V and 5.5 V. The device generates regulated current sinks with high absolute and channel-to-channel accuracy to drive up to 4 LEDs. It can support LEDs with forward voltage as high as 3.8 V. The current sink for each channel can be set with 4 individual external resistors. Each channel is controlled independently. The PWM control can be applied directly to the 4 EN (enable) pins to provide brightness control. When enabled, the charge pump, which uses a small ceramic bucket capacitor between C P and C N, operates to regulate the V OUT with a clamping voltage at typ. 5 V. The tiny QFN0 (.8x3. mm) package allows the device to be also used for applications with space limitations. Table : Device summary Oder code Package Packing QTR QFN0 (.8x3. mm) Tape and reel April 05 DocID5770 Rev 3 /4 This is information on a product in full production.

2 Contents Contents Application schematic... 5 Pin configuration Maximum ratings Electrical characteristics Detailed description Enable pin LED turn-on pin (ONx) Programmable output current Charge pump Thermal protection... 6 Typical performance characteristics... 7 PCB layout Recommended Evaluation board Package information QFN0 (.8x3. mm) package information Packing information... 9 Revision history... 3 /4 DocID5770 Rev 3

3 List of tables List of tables Table : Device summary... Table : Typical external components... 5 Table 3: Pin description... 7 Table 4: Absolute maximum ratings... 8 Table 5: Recommended operating conditions... 8 Table 6: Thermal data... 8 Table 7: Electrical characteristics... 9 Table 8: QFN0 (.8x3. mm) package mechanical data... 0 Table 9: Document revision history... 3 DocID5770 Rev 3 3/4

4 List of figures List of figures Figure : Application schematic... 5 Figure : Block schematic... 6 Figure 3: Pin connections (top view)... 7 Figure 4: Efficiency vs. V IN, I OUT = 0 ma... Figure 5: Efficiency vs. V IN, I OUT = 60 ma... Figure 6: V OUT vs. V IN... 3 Figure 7: PWM modulation CH Figure 8: Output ripple... 4 Figure 9: Top layer... 5 Figure 0: Bottom layer... 6 Figure : Top overlay... 6 Figure : Evaluation board... 7 Figure 3: Evaluation board schematic... 7 Figure 4: QFN0 (.8x3. mm) package outline... 9 Figure 5: QFN0 (.8x3. mm) recommended footprint... 0 Figure 6: QFN0 (.8x3. mm) carrier tape outline... Figure 7: QFN0 (.8x3. mm) reel outline... 4/4 DocID5770 Rev 3

5 Application schematic Application schematic Figure : Application schematic ON ON ON3 ON4 EN GND C N C P V OUT V CC C C C OUT R SET I SET LED C3 LED R SET I SET LED LED R SET3 I SET3 LED3 LED3 R SET4 I SET4 GND LED4 CP_Sel LED4 GIPG LM The above figure shows the typical application diagram with the external components. To ensure an optimal charge pump performance, it is highly recommended that the bucket capacitor, C, and the output capacitor, C OUT, to be placed as close as possible to the pins. Table : Typical external components Component Manufacturer Part number Value Size C,C OUT C C3 R SET-4 () LED-4 () Murata TDK Murata TDK Murata TDK GRM55R6A05KE5D C005X5RA05MT GRM88R60J06ME84 C608X5R0J06MT GRM55R60J04KA0D C005X5RC04KT µf/0 V µf/6.3 V nf 040 Tyco CPF040B976RE 976 Ω 040 Notes: () 649 Ω to 7.87 kω according to the desired output current from each channel. () Forward voltage typ. 3.8 V. All the above components refer to a typical application. Operation of the device is not limited to the choice of these external components. DocID5770 Rev 3 5/4

6 Application schematic Figure : Block schematic C P C N V CC V OUT CP_Sel Charge pump EN ON ON ON3 ON4 Thermal protection LED3 Current mirrors LED LED LED3 LED4 Bandgap reference GND I SET I SET I SET3 I SET4 R SET R SET R SET3 R SET4 GPG LM 6/4 DocID5770 Rev 3

7 Pin configuration Pin configuration Figure 3: Pin connections (top view) 9 GIPG LM Table 3: Pin description Pin Symbol Description ON LED enable ON LED enable 3 ON3 LED3 enable 4 ON4 LED4 enable 5 EN Chip enable 6 I SET LED max. current setting resistor 7 I SET LED max. current setting resistor 8 I SET3 LED3 max. current setting resistor 9 I SET4 LED4 max. current setting resistor 0 GND Ground CP_SEL Charge pump mode selection, = enable 0 = disable LED4 4 th LED current sink 3 LED3 3 rd LED current sink 4 LED nd LED current sink 5 LED st LED current sink 6 V CC Supply voltage 7 V OUT Charge pump output 8 C P Positive terminal of charge pump bucket capacitor 9 C N Negative terminal of charge pump bucket capacitor 0 GND Ground DocID5770 Rev 3 7/4

8 Maximum ratings 3 Maximum ratings Table 4: Absolute maximum ratings Symbol Parameter Value Unit ON -4, V CC, EN, CP_SEL, C P, C N Supply voltage to V VOUT Output voltage to V LED-4, I SET-4 Current setting -0.3 to V ESD Human body model ±500 Charged device model ±500 Machine model ±00 T AMB Operating ambient temperature - 30 to 85 C T J Maximum operating junction temperature V +50 C T STG Storage temperature -65 to 50 C Table 5: Recommended operating conditions Symbol Parameter Min. Typ. Max. Unit V CC Supply voltage V T op Operating temperature C I LED T pwm_on T pwm_off Current through each LED ON time of PWM signal at each ON pin OFF time of PWM signal at each ON pin.5 30 ma 33 µs V fw LED forward voltage 3.8 V Table 6: Thermal data Symbol Parameter Value Unit R thja () Thermal resistance junction-ambient 70 C/W Notes: () This parameter corresponds to the PCB board, 4-layer with inch of cooling area. 8/4 DocID5770 Rev 3

9 Electrical characteristics 4 Electrical characteristics V CC = 3.3 V, V EN = V ON = V ON = V ON3 = V ON4 = V CC, V CP_SEL = V CC, R SET = R SET = R SET3 = R SET4 = 649 Ω, C = µf, typical values are at T A = 5 C unless otherwise specified. Table 7: Electrical characteristics Symbol Parameter Test conditions Min. Typ. Max. Unit V CC Supply voltage V V cp_clamp T cp_start I LED,,3,4 I LED V IH V IL I CC I SHUTDOWN Charge pump clamp voltage Charge pump startup time LED sink current for each channel Output current error between each channel High level input voltage Low level input voltage Supply operating current Supply current during power-down.7 V V CC < 3. V; V CP_SEL = V CC; I OUT 40 ma V CC > 3. V; V CP_SEL = V CC; I OUT 0 ma From CP_SEL low to high transition to CP reaches steady-state 5 V R setx = 649 Ω at V LEDx= 0.9 V; V CC > 3. V R setx = 7.87 kω at V LEDx= 0.9 V; V CC 3. V R SET = R SET, R SET3 = R SET4, T A = 5 C V ON = V ON = V ON3 = V ON4 = GND; no-load; V CC = 5.5 V (charge pump disabled); V CP_SEL = GND, R SET = R SET = R SET3 = R SET4 = 7.87 kω V ON = V ON = V ON3 = V ON4 = GND; no-load; V CC = 5.5 V (charge pump disabled); V CP_SEL = GND, R SET = R SET = R SET3 = R SET4= 649 Ω V ON = V ON = V ON3 = V ON4 = GND; no-load; V CC = 3.3 V (charge pump enabled); V CP_SEL = V CC, R SET = R SET = R SET3 = R SET4= 7.87 kω V ON = V ON = V ON3 = V ON4 = GND; no-load; V CC = 3.3 V (charge pump enabled); V CP_SEL = V CC, R SET = R SET = R SET3 = R SET4 = 649 Ω V EN = V ON = V ON = V EN = V ON3 = V ON4 =V CP_SEL = 0 V 5 V 5 0 ms ma ma.0 ± ±4 % V ma 5 µa DocID5770 Rev 3 9/4

10 Electrical characteristics Symbol Parameter Test conditions Min. Typ. Max. Unit T SD Thermal shutdown 50 C T HS Thermal shutdown hysteresis 5 C 0/4 DocID5770 Rev 3

11 Detailed description 5 Detailed description The is a charge-pump-based 4-channel LED driver designed for RGB illumination or LCD display backlighting, using constant current topology. Each of the 4 channels can be controlled independently. When ONx is pulled high, a constant current is sunk into the LEDx pin when one LED is connected. This constant current is defined or programmed by the value of the resistor on the I SETX pin. 5. Enable pin The active high enable input pin is used to shut down the whole device. When this pin is pulled low, the device goes into shutdown mode with 5 μa max. current consumption only. An internal pulled down of 300 kω is present on this pin. 5. LED turn-on pin (ONx) When the EN pin is pulled high, the provides the flexibility to control ON/OFF on the 4 channels independently through the 4 active high ON pins. To control the brightness of each LED channel, it is possible to drive the selected ON pin with a PWM signal with a frequency up to min. 33 μs T ON /T OFF. An internal pull-down of 300 kω is present on these pins. 5.3 Programmable output current The LED currents on the 4 channels are programmed individually through a resistor connected from I SET, I SET, I SET3, I SET4 to ground. The relationship between the resistor (R SET ) and the LED current (I LED ) is given by the below equation: R SET = 6x(./I LED ) 5.4 Charge pump The charge pump can be disabled or enabled according to the CP_SEL pin. When enabled (CP_SEL is high), the charge pump provides a clamping voltage of typ. 5.0 V to ensure enough headroom to drive the LEDs. An internal pull-down of 300 kω is present on this pin. The charge pump can be disabled by pulling low the CP_SEL pin, based on the V CC and forward voltage of the LEDs used. This allows the connection of V CC directly to V OUT to drive the external LEDs. At V CC 3. V, the charge pump maintains regulation at 5 V when the total current drawn from it (on V OUT pin) is 0 ma. At.7 V CC < 3. V, in order for the charge pump to maintain regulation at 5 V, the total current drawn from it (on V OUT pin) must be lowered to 40 ma. 5.5 Thermal protection The thermal protection circuit ensures the device shutdown when it is overheated (for example, due to an output short-circuit) to typ. 50 C. The device resumes normal operation when the temperature drops by 5 C from the thermal shutdown threshold. DocID5770 Rev 3 /4

12 Eff [%] Eff [%] IIN[mA] Typical performance characteristics 6 Typical performance characteristics Figure 4: Efficiency vs. V IN, I OUT = 0 ma EFF IIN VIN [V] Figure 5: Efficiency vs. V IN, I OUT = 60 ma EFF Iin V IN [V] GIPG LM IIN [ma] GIPG LM /4 DocID5770 Rev 3

13 Typical performance characteristics Figure 6: V OUT vs. V IN VOUT [V] V IN [V] GIPG LM Figure 7: PWM modulation CH- DocID5770 Rev 3 3/4

14 Typical performance characteristics Figure 8: Output ripple 4/4 DocID5770 Rev 3

15 PCB layout 7 PCB layout 7. Recommended The is a charge pump power device so it requires a proper PCB layout in order to obtain the necessary stability and optimize line/load regulation and output voltage ripple. Input, output, and boost capacitors must be as close as possible to their relative pins. Figure 9: Top layer DocID5770 Rev 3 5/4

16 PCB layout Figure 0: Bottom layer Figure : Top overlay 6/4 DocID5770 Rev 3

17 0 7. Evaluation board Figure : Evaluation board PCB layout Figure 3: Evaluation board schematic V CC 3 VCC JP3 VCC 3 JP4 VC C 3 JP5 VCC 3 JP6 3 JP P3 P5 P P4 Pull-down resistors R-R6 to guarantee the correct function when no jumper is placed. For efficiency measurements, resistors should be removed to measure the correct DUT input current, otherwise the pull-down resistor current affects the result. VCC CP_SEL 3 JP R3 0k R4 0k R5 0k R6 0k R 0k R0 R 7 R 8 R9 R k k k k 0k ON ON GND 0 VCC VCC VCC ON CN CN 9 ON3 3 ON CP CP 8 ON4 4 ON3 VOUT VOUT 7 EN 5 ON4 VCC VCC 6 ISET 6 EN LED 5 ISET 7 ISET LED 4 ISET3 8 ISET 3 LED3 ISET4 9 ISET3 ISET4 LED4 GND CP_SEL P U LED LED LED3 LED4 C 0µF C3 00n C µf LED4 LED3 LED LED VOUT C4 µf P6 P6- P0 header areusedto loadoutputs whenno LED is populated. P7 P9 P8 P0 Pulldown resistors R7-R0 are set resistors for each channel. Needed to be changed for different output current setup. GIPG LM DocID5770 Rev 3 7/4

18 Package information 8 Package information In order to meet environmental requirements, ST offers these devices in different grades of ECOPACK packages, depending on their level of environmental compliance. ECOPACK specifications, grade definitions and product status are available at: ECOPACK is an ST trademark. 8/4 DocID5770 Rev 3

19 Package information 8. QFN0 (.8x3. mm) package information Figure 4: QFN0 (.8x3. mm) package outline DocID5770 Rev 3 9/4

20 Package information Table 8: QFN0 (.8x3. mm) package mechanical data mm Dim. Min. Typ. Max. A A A3 0.7 b D E e 0.40 L Figure 5: QFN0 (.8x3. mm) recommended footprint 0/4 DocID5770 Rev 3

21 Package information 8. Packing information Figure 6: QFN0 (.8x3. mm) carrier tape outline DocID5770 Rev 3 /4

22 Package information Figure 7: QFN0 (.8x3. mm) reel outline Drawing is not in scale and dimensions are in mm /4 DocID5770 Rev 3

23 Revision history 9 Revision history Table 9: Document revision history Date Revision Changes 09-Jun-009 Initial release. 4-Jan-0 09-Apr-05 3 Updated features. Document status promoted from preliminary data to datasheet. Added section 7. DocID5770 Rev 3 3/4

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