The MAX8901A/MAX8901B are step-up converters designed to drive two to six series-connected white LEDs (WLEDs) with constant current for uniform WLED intensity in LCD backlighting for cell phones, PDAs, and other handheld devices. The converters operate at a fixed 750kHz (typ) switching frequency, allowing for small external components, and are optimized for high efficiency over the entire 1-cell Li+/Li-Poly battery range. These converters use a single input (ON) to enable the IC and control WLED intensity. The MAX8901A requires a direct PWM input to regulate WLED intensity, with the WLED current proportional to the PWM duty cycle. The MAX8901B uses single-wire, serial-pulse dimming to reduce WLED intensity in 32 linear steps. The full-scale WLED current for serial-pulse dimming is 24.75mA (MAX8901B, 0.75mA/step). The MAX8901_ features an internal soft-start to eliminate inrush currents during startup, input overvoltage protection, WLED overvoltage protection, and a shutdown mode with 0.01µA (typ) shutdown current. No WLED current is present in shutdown mode if the WLED forward voltage is greater than the input supply voltage. Additional features include undervoltage lockout (UVLO) and thermal shutdown. The MAX8901_ is available in a small 8-pin, 2mm x 2mm TDFN-EP package (maximum height 0.8mm).
The MAX8901A and MAX8901B are step‑up converters that drive two to six series‑connected white LEDs for LCD backlighting in cell phones, PDAs, and other handheld devices. They operate from a single‑cell Li‑ion or Li‑Poly battery and provide constant‑current LED drive.
The devices feature a fixed 750 kHz switching frequency, up to 91 % efficiency, and support PWM dimming (MAX8901A) or 32‑step serial‑pulse dimming (MAX8901B). They include internal soft‑start, UVLO, over‑voltage protection, and thermal shutdown, and are offered in a 2 mm × 2 mm TDFN package.
| Input Voltage Range | 2.6 V to 5.5 V |
|---|---|
| Switching Frequency | 750 kHz (typ) |
| Efficiency | up to 91 % |
| Shutdown Current | 0.01 µA (typ) |
| Input Overvoltage Lockout Threshold | 6.2 V to 6.3 V (Vin rising) |
| Operating Temperature Range | -40 °C to +85 °C |
| Package Type | 2 mm × 2 mm TDFN (8‑pin) |
The device operates from 2.6 V to 5.5 V.
It uses a direct PWM input where the LED current is proportional to the PWM duty cycle.
The typical shutdown current is 0.01 µA.
They are offered in an 8‑pin 2 mm × 2 mm TDFN package.