TPS92511 500-mA, 65-V Common Anode Constant Current Buck LED Driver Without External Current Sensing Resistor
1 Features
- Wide Input Voltage Range: 4.5 V to 65 V
- Requires NO External Current Sensing Resistor
- Requires NO External Loop Compensation
- Ease of Use, Needs Minimum 5 Components
- 1000:1 Contrast Ratio Feasible
- Single Layer PCB Feasible
- Can Work as High Voltage Buck Regulators
- Can Work as Linear Current Shunt Regulators
- Integrated Low-side N-channel MOSFET
- LED Current Programmable up to 0.5 A
- Typically ±3.6% LED Current Accuracy
- Switching Frequency Programmable From 50 kHz to 500 kHz
- Current Limit Protection
- VCC Under-voltage Lock-out
- Thermal Shutdown Protection
- Support Analog Dimming and Thermal Foldback
- Power Enhanced SOIC-8 Exposed Thermal Pad Package (HSOP-8)
2 Applications
- High Power LED Driver
- Architectural Lighting
- Office Troffer
- Automotive Lighting
- MR-16 LED Lamp
3 Description
The TPS92511 is an easy to use 65V constant current buck converter for driving a single LED string with current up to 0.5A and efficiency up to 95%. Only 5 external components are required for basic operation and single layer PCB layout is feasible because of the integration of a N-MOSFET, no external current sensing resistor, no external compensation and the proper terminal assignment. A high-value external resistor programs the LED current so that fine tuning of the LED current can be achieved. Another high-value external resistor programs a constant switching frequency from 50kHz to 500kHz. EMI design becomes easier as a result of constant switching frequency. The TPS92511 provides a wide input voltage range from 4.5V to 65V. By adding simple external circuits, the device can handle applications with even higher input voltages.
The TPS92511 employs a proprietary control scheme to regulate the LED current without the need of sensing the LED current directly. It applies a floating buck topology with a low-side N-channel power MOSFET, which does not need boot-strapping capacitor. For multiple channel systems, the floating buck topology together with the proprietary control scheme allows a common-anode connection of the LED strings without an external current sensing network. This significantly reduces the number of wiring and as well as overall manufacturing cost.
The TPS92511 has very fast PWM dimming response time. For example, if the switching frequency is 500 kHz, the minimum DIM pulse width is 6µs and the dimming frequency is 150Hz, a contrast ratio of more than 1000:1 can be achieved.
The TPS92511 is available in the Power Enhanced SOIC-8 exposed thermal pad package.
- For all available packages, see the orderable addendum at the end of the datasheet.
5 Pin Configuration and Functions
Pin Functions
| PIN | DESCRIPTION | |
|---|---|---|
| NAME | NO. | |
| DIM | 6 | PWM Dimming Control. Apply logic level PWM signal to this pin dims the LED string. This pin is internally pulled up. |
| FS | 5 | Switching Frequency Setting. An external resistor RFS connecting the FS pin to ground programs the switching frequency from 50 kHz to 500 kHz. |
| GND | 4 | Analog Signal Ground. |
| IADJ | 3 | Average LED Current Setting. An external resistor RIADJ connecting the IADJ pin to ground programs the average LED current. |
| LX | 7 | Integrated MOSFET Drain. Internally connected to the drain of the integrated MOSFET. Connect this pin to the output inductor and anode of the Schottky diode. |
| PGND | 2 | Power Ground. Must be connected to the GND pin for normal operation. The PGND and GND pins are not internally shorted. |
| VCC | 1 | Internal Regulator Output. Typically regulated to 5.4 V. Connect a capacitor of larger than 1 µF between the VCC and GND pins. |
| VIN | 8 | Input Voltage. Supply pin to the device. The input voltage range is from 4.5 V to 65 V. |
| Thermal pad | Thermal Connection Pad. Connect to a ground plane for heat dissipation. | |