Datenblatt-Suchmaschine für elektronische Bauteile |
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STP2CMP Datenblatt(PDF) 10 Page - STMicroelectronics |
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STP2CMP Datenblatt(HTML) 10 Page - STMicroelectronics |
10 / 23 page Detailed description STP2CMP 10/23 DocID022734 Rev 2 5 Detailed description The STP2CMP is a charge-pump-based 2-channel LED driver designed for mobile phone display backlighting, using constant current topology. Each of the 2 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 (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 pull-d own of 300 kΩ is present on this pin. 5.2 LED turn-on pin (ONx) When the EN pin is pulled high, the STP2CMP provides the flexibility to control the turning on/off on the 2 channels independently through the 2 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 TON/TOFF of 33 µs. An internal pull-down of 300 kΩ is present on these pins. 5.3 Programmable output current The LED currents at the 2 channels are programmed individually through a resistor connected from ISET1, ISET2 to ground. The relationship between the resistor (RSET) and the LED current (ILED) is governed by the below equation: RSET = 16 x (1.22/ILED) 5.4 Charge pump The STP2CMP 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 (at VOUT pin) is ≤ 120 mA. At 2.7 ≤ VCC < 3.1 V so that the charge pump maintains the 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 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. |
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