STP4CMPQTR STMICROELECTRONICS | Alldatasheet
Document overview
- Manufacturer or author: Provided By ALLDATASHEET.COM(FREE DATASHEET DOWNLOAD SITE)
- PDF pages: 22
Technical content
Datasheet sections
- 1 Schematic
- 2 Pin configuration
- 3 Maximum ratings
- 4 Electrical characteristics
- 5 Detailed description
- 5.1 Enable pin (EN)
- 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 Demonstration board
- 7.3 Demonstration board schematic
- 8 Package mechanical data
- 9 Revision history
Features
■ Operating voltage range: VCC (opr) = 2.7 V to 5.5 V ■ Full RGB function support ■ 4-channel LED driver with individual ON/OFF control directly from input pins ■ Individual 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. ± ■ Selectable charge pump enable/disable ■ Thermal protection ■ Small QFN20 (1.8 x 3.2 mm) package
Applications
■ Mobile phone display backlighting ■ RGB LED indicator drivers
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 - 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 V OUT with a clamping voltage at typ. 5 V. The tiny QFN20 (1.8 x 3.2 mm) package allows the device to be also used for applications with space limitation. QFN20 (1.8 x 3.2 mm) Table 1. Device summary
1 Schematic
Figure 1. Application schematic OUT, to be placed as close as possible to the pins. to the choice of these external components. Table 2. Typical external components
- R SET1-4: 649 Ω - 7.87 kΩ according to the desired output current from each channel.
- LED1-4: typ. forward voltage of 3.8 V.
Figure 2. Block schematic
2 Pin configuration
Figure 3. Pin connection (top through view) Table 3. Pin description
1 ON1 LED1 enable
2 ON2 LED2 enable
3 ON3 LED3 enable
4 ON4 LED4 enable
5 EN Chip enable
10 GND Ground
11 CP_Sel Charge pump mode selection, ‘1’ => enable; ‘0’ => disable
12 LED4 4 th LED current sink
13 LED3 3 rd LED current sink
14 LED2 2 nd LED current sink
15 LED1 1 st LED current sink
16 V CC Supply voltage
17 V OUT Charge pump output
18 C 1P Positive terminal of charge pump bucket capacitor
19 C 1N Negative terminal of charge pump bucket capacitor
20 GND Ground
Table 3. Pin description (continued)
3 Maximum ratings
Note: Absolute maximum ratings are those values beyond which damage to the device may occur. Functional operation under these conditions is not implied. Table 4. Absolute maximum ratings Table 5. Recommended operating conditions Table 6. Thermal data
- This parameter corresponds to the PCB boar d, 4-layers with 1inch² of cooling area.
4 Electrical characteristics
RSET4= 649 Ω, C1 =1 µF , typical values are at TA=25°C, unless otherwise specified. Table 7. Electrical characteristics
Table 7. Electrical characteristics (continued)
Detailed description STP4CMP 10/22 Doc ID 15770 Rev 2
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 a LED is connected. This constant current is defined or programmed by the value of the resistor at I SETX pin.
5.1 Enable pin (EN)
The active high enable input pin is used to shut down the whole device. When this pin is pulled low, the device enters into shutdown mode with only 5 µA max. current consumption. An internal pulled down of 300 kΩ is present at this pin.
5.2 LED turn-on pin (ONx)
When the EN pin is pulled high, the STP4CMP provides the flexibility to control the turning- 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 a minimum T ON/TOFF of 33 µs. An internal pull-down of 300 kΩ is present at these pins.
5.3 Programmable output current
The LED currents at the 4 channels are programmed individually through a resistor connected from I set1, Iset2, Iset3, Iset4 to ground. The relationship between the resistor (RSET) and the LED current (ILED) is governed by this equation: Equation 1 RSET = 16 * (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 at 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 VCC directly to VOUT to drive the external LEDs. At VCC 3.1 V, the charge pump is able to maintain regulation at 5 V when the total current drawn from it (at 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 (at VOUT pin) must be lowered to ≤ 40 mA.
STP4CMP Detailed description Doc ID 15770 Rev 2 11/22
5.5 Thermal protection
The thermal protection circuit ensures 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.
6 Typical performance characteristics
Figure 4. Eff. vs.V IN, IOUT = 10 mA Figure 5. Eff. vs.V IN, IOUT = 60 mA Figure 6. V OUT vs.VIN
7 PCB layout
7.1 Recommended
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 Figure 10. Bottom layer
Figure 11. Top overlay
7.2 Demonstration board
Figure 12. Demonstration board
7.3 Demonstration board schematic
Figure 13. Demonstration board schematic function wh en n o jump e r is place d.
8 Package mechanical data
- Dimensions are in millimeters.
- Dimensions are in millimeters
9 Revision history
Table 9. Document revision history 09-Jun-2009 1 Initial release. 24-Jan-2012 2 Document status promoted from preliminary data to datasheet.