LM27961 is a charge-pump-based white-LED driver that is ideal for mobile phone display backlighting. It can drive 4 LEDs for a main phone display backlight and 3 LEDs for a sub-display backlight. The driver provides excellent current and brightness matching in all LEDs. The LED driver current sources are split into two independently controlled groups. The primary group (Group A) can be used to backlight a main phone display with up to 4 LEDs, with low-side current drivers accommodating common-anode-type LEDs. The second group (Group B) can backlight a secondary display with up to 3 LEDs, with high-side current drivers accommodating common-cathode-type LEDs. Both Group A and Group B can also drive standard two-terminal LEDs, and provide other general lighting functions (keypad lighting, fun lighting, etc). The brightness of the two LED groups can be adjusted independently with external resistors. The LM27961 works off an extended Li-Ion input voltage range (2.7V to 5.5V), achieving voltage boost with a high-efficiency 3/2x-gain charge pump. The LM27961 is available in National’s chip-scale 18-bump micro SMD package.
The LM27961 is a charge‑pump‑based LED driver designed for mobile phone display backlighting. It provides two independently controlled LED groups: Group A for up to four common‑anode LEDs (main display) and Group B for up to three common‑cathode LEDs (sub‑display). Current for each LED is programmable with external resistors, and brightness can be dimmed via a PWM signal.
The device operates from a 2.7 V to 5.5 V Li‑ion input, uses a high‑efficiency 3/2× charge pump, and is supplied in an 18‑bump thin micro‑SMD package. Typical applications include mobile phone display lighting, keypad lighting, PDAs, and general LED lighting.
| Input voltage range | 2.7 V to 5.5 V |
|---|---|
| LED drive current per LED | up to 20 mA each |
| Maximum LEDs per group | Group A: up to 4 LEDs, Group B: up to 3 LEDs |
| PWM brightness control frequency | 100 Hz – 1 kHz |
| Charge‑pump gain | 3/2× |
The LM27961 operates from 2.7 V up to 5.5 V.
Group A can drive up to four LEDs, while Group B can drive up to three LEDs.
Brightness can be dimmed with a PWM signal between 100 Hz and 1 kHz.