STP4CMP STMICROELECTRONICS | Alldatasheet
Document overview
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- PDF pages: 24
Technical content
Datasheet sections
- 1 Application schematic
- 2 Pin configuration
- 3 Maximum ratings
- 4 Electrical characteristics
- 5 Detailed description
- 5.1 Enable pin
- 5.2 LED turn-on pin (ONx)
- 5.3 Programmable output current
- 5.4 Charge pump
- 5.5 Thermal protection
- 6 Typical performance characteristics
- 7 PCB layout
- 7.1 Recommended
- 7.2 Evaluation board
- 8 Package information
- 8.2 Packing information
- 9 Revision history
Features
Operating voltage range: VCC 2.7 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 QFN20 (1.8x3.2 mm) package
Applications
Mobile phone display backlighting RGB LED indicator driver
Description
The STP4CMP is a charge-pump-based 4- channel LED driver designed for RGB illumination or LCD display backlighting. The STP4CMP works off a battery with an input voltage between 2.7 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 C1P and C1N, operates to regulate the VOUT with a clamping voltage at typ. 5 V. The tiny QFN20 (1.8x3.2 mm) package allows the device to be also used for applications with space limitations. Table 1: Device summary Oder code Package Packing STP4CMPQTR QFN20 (1.8x3.2 mm) Tape and reel QFN20 (1.8x3.2 mm)
1 Application schematic
Figure 1: Application schematic 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, C1, and the output capacitor, COUT, to be placed as close as possible to the pins. Table 2: Typical external components Component Manufacturer Part number Value Size C1,COUT Murata GRM155R61A105KE15D 1 µF/10 V 0402 TDK C1005X5R1A105MT Murata GRM188R60J106ME84 10 µF/6.3 V 0603 TDK C1608X5R0J106MT Murata GRM155R60J104KA01D 100 nF 0402 TDK C1005X5R1C104KT RSET1-4 (1) Tyco CPF0402B976RE1 976 Ω 0402 LED1-4 (2) Notes: (1)649 Ω to 7.87 kΩ according to the desired output current from each channel. (2)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. LED2 LED3 LED4 C1N ON1 ON2 ON3 C1P ISET1 GND EN LED1 VOUT VCC RSET1 ON4 ISET2 RSET2 ISET3 RSET3 ISET4 RSET4 CP_Sel GND COUT LED1 LED2 LED3 LED4 GIPG270320151334LM
Figure 2: Block schematic Charge pump Current mirrors ON1 ON2 ON3 C1P ISETGND EN LED2 LED3 ON4 CP_Sel Thermal protection Bandgap reference LED4 LED1 LED3 C1N VCC VOUT
1 ISET2 ISET3 ISET4
2 Pin configuration
Figure 3: Pin connections (top view) Table 3: Pin description Pin Symbol Description
1 ON1 LED1 enable
2 ON2 LED2 enable
3 ON3 LED3 enable
4 ON4 LED4 enable
5 EN Chip enable
6 ISET1 LED1 max. current setting resistor 7 ISET2 LED2 max. current setting resistor 8 ISET3 LED3 max. current setting resistor 9 ISET4 LED4 max. current setting resistor
10 GND Ground
11 CP_SEL Charge pump mode selection, 1 = enable 0 = disable
12 LED4 4th LED current sink
13 LED3 3rd LED current sink
14 LED2 2nd LED current sink
15 LED1 1st LED current sink
16 VCC Supply voltage
17 VOUT Charge pump output
18 C1P Positive terminal of charge pump bucket capacitor
19 C1N Negative terminal of charge pump bucket capacitor
20 GND Ground
3 Maximum ratings
Table 4: Absolute maximum ratings Symbol Parameter Value Unit ON1-4, VCC, EN, CP_SEL, C1P, C1N Supply voltage - 0.3 to + 6.0 V VOUT Output voltage - 0.3 to + 6.0 V LED1-4, ISET1-4 Current setting -0.3 to 2 V ESD Human body model ±1500 V Charged device model ±500 Machine model ±200 TAMB Operating ambient temperature - 30 to 85 °C TJ Maximum operating junction temperature +150 °C TSTG Storage temperature -65 to 150 °C Table 5: Recommended operating conditions Symbol Parameter Min. Typ. Max. Unit VCC Supply voltage 2.7 5.5 V Top Operating temperature -40 85 °C ILED Current through each LED 2.5 30 mA Tpwm_ON ON time of PWM signal at each ON pin 33 µs Tpwm_OFF OFF time of PWM signal at each ON pin Vfw LED forward voltage 3.8 V Table 6: Thermal data Symbol Parameter Value Unit RthJA (1) Thermal resistance junction-ambient 70 °C/W Notes: (1)This parameter corresponds to the PCB board, 4-layer with 1 inch2 of cooling area.
4 Electrical characteristics
VCC = 3.3 V, VEN = VON1 = VON2 = VON3 = VON4 = VCC, VCP_SEL = VCC, RSET1 = RSET2 = RSET3 = RSET4 = 649 Ω, C1 = 1 µF, typical values are at TA = 25 °C unless otherwise specified. Table 7: Electrical characteristics Symbol Parameter Test conditions Min. Typ. Max. Unit VCC Supply voltage 2.7 5.5 V Vcp_clamp Charge pump clamp voltage 2.7 V ≤ VCC < 3.1 V; VCP_SEL = VCC; IOUT ≤ 40 mA V VCC > 3.1 V; VCP_SEL = VCC; IOUT ≤ 120 mA Tcp_start Charge pump start- up time From CP_SEL low to high transition to CP reaches steady-state 5 V 10 ms ILED1,2,3,4 LED sink current for each channel Rsetx = 649 Ω at VLEDx= 0.9 V; VCC > 3.1 V 27.9 30 32.1 mA Rsetx = 7.87 kΩ at VLEDx= 0.9 V; VCC ≥ 3.1 V 2.33 2.5 2.68 mA ∆ILED Output current error between each channel RSET1 = RSET2, RSET3 = RSET4, TA = 25 °C ±1 ±4 % VIH High level input voltage 2.0 V VIL Low level input voltage 0.8 ICC Supply operating current VON1 = VON2 = VON3 = VON4 = GND; no-load; VCC = 5.5 V (charge pump disabled); VCP_SEL = GND, RSET1 = RSET2 = RSET3 = RSET4 = 7.87 kΩ 3.6 mA VON1 = VON2 = VON3 = VON4 = GND; no-load; VCC = 5.5 V (charge pump disabled); VCP_SEL = GND, RSET1 = RSET2 = RSET3 = RSET4= 649 Ω 1.7 VON1 = VON2 = VON3 = VON4 = GND; no-load; VCC = 3.3 V (charge pump enabled); VCP_SEL = VCC, RSET1 = RSET2 = RSET3 = RSET4= 7.87 kΩ 4.5 VON1 = VON2 = VON3 = VON4 = GND; no-load; VCC = 3.3 V (charge pump enabled); VCP_SEL = VCC, RSET1 = RSET2 = RSET3 = RSET4 = 649 Ω 17.2 ISHUTDOWN Supply current during power-down VEN = VON1 = VON2 = VEN = VON3 = VON4 =VCP_SEL = 0 V 5 µA
Symbol Parameter Test conditions Min. Typ. Max. Unit TSD Thermal shutdown 150 THS Thermal shutdown hysteresis
STP4CMP Detailed description
5 Detailed description
The STP4CMP 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 ISETX pin.
5.1 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.
5.2 LED turn-on pin (ONx)
When the EN pin is pulled high, the STP4CMP 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 TON/TOFF. 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 ISET1, ISET2, ISET3, ISET4 to ground. The relationship between the resistor (RSET) and the LED current (ILED) is given by the below equation: RSET= 16x(1.22/ILED)
5.4 Charge pump
The STP4CMP 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 VCC and forward voltage of the LEDs used. This allows the connection of VCC directly to VOUT to drive the external LEDs. At VCC 3.1 V, the charge pump maintains regulation at 5 V when the total current drawn from it (on VOUT pin) is ≤ 120 mA. At 2.7 ≤ VCC < 3.1 V, in order for the charge pump to maintain regulation at 5 V, the total current drawn from it (on VOUT 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. 150 °C. The device resumes normal operation when the temperature drops by 15 °C from the thermal shutdown threshold.
Typical performance characteristics STP4CMP
6 Typical performance characteristics
Figure 4: Efficiency vs. VIN, IOUT = 10 mA Figure 5: Efficiency vs. VIN, IOUT = 60 mA 100 IIN[mA] Eff[%] VIN [V] EFF IIN GIPG260320150908LM 200 210 220 230 240 250 260 100 IIN [mA] Eff[%] VIN [V] EFF Iin GIPG260320150922LM
Typical performance characteristics STP4CMP Figure 8: Output ripple
7 PCB layout
7.1 Recommended
The STP4CMP 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 ri pple. Input, output, and boost capacitors must be as close as possible to their relative pins. Figure 9: Top layer
7.2 Evaluation board
Figure 12: Evaluation board Figure 13: Evaluation board schematic VCC VCC C1N C1P VOUT LED1 LED2 LED3 LED4 VCC 10k 10k 10k 10k 10k 1kR7 1kR8 1kR9 1k R10 10 k VOUT JP5 VCC JP1 VCC JP3 VCC 1 JP4 VC C JP6 VCC JP2 1µFC4 1µF 10µF VCC 100n P10 VCC CP_SEL ISET1 ISET2 ISET3 ISET4 ON 1 ON2 ON3 ON4 EN LED4 LED3 LED2 LED1 C1N 19 C1P 18 VOUT 17 VCC 16 LED1 15 LED2 14 LED3 13 LED4 12ISET49 ISET38 ISET27 ISET16 EN5 ON44 ON33 ON22 ON1 1 GND 20 GND10 CP_SEL STP4CMP Pull -down resistors R1- R6 to guarantee the correct function when no jumper is placed. For efficiency measurements, resistor s should be removed to measure the correct DUT input current, otherwise the pull-down resistor current affects the result. Pull down resistors R7-R10 are set resistors for each channel. Needed to be changed for different output current setup. P6- P10 header areusedto loadoutputs whennoLED is populated. GIPG310320151040LM
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: www.st.com. ECOPACK is an ST trademark.
8.1 QFN20 (1.8x3.2 mm) package information Figure 14: QFN20 (1.8x3.2 mm) package outline
Table 8: QFN20 (1.8x3.2 mm) package mechanical data Dim. mm Min. Typ. Max. A 0.45 0.50 0.55 A1 0 0.02 0.05 0.127 b 0.15 0.20 0.25 D 3.15 3.20 3.25 E 1.75 1.80 1.85 e 0.40 L 0.35 0.40 0.45 Figure 15: QFN20 (1.8x3.2 mm) recommended footprint
8.2 Packing information
Figure 16: QFN20 (1.8x3.2 mm) carrier tape outline
Figure 17: QFN20 (1.8x3.2 mm) reel outline Drawing is not in scale and dimensions are in mm
9 Revision history
Table 9: Document revision history Date Revision Changes 09-Jun-2009 1 Initial release. 24-Jan-2012 2 Document status promoted from preliminary data to datasheet. Added section 7. 09-Apr-2015 3 Updated features.