LM2751
www.ti.com SNVS299B – APRIL 2005 – REVISED MAY 2013 LM2751 Regulated 2X, 1.5X Switched Capacitor White LED Driver
Check for Samples: LM2751 FEATURES APPLICATIONS 1 2 Regulated Output Options: 4.5V, 5.0V
Output Voltage Regulated Within 3%
Peak Efficiency Over 90%
150mA (4.5V) or 80mA (5.0V) Output Current
Capability
Input Voltage Range: 2.8V to 5.5V
Low Input and Output Voltage Ripple TON
fMAX = DMIN Г TON (2)
(3) The minimum recommended PWM frequency is 100Hz. Frequencies below this may be visibly noticeable as
flicker or blinking. The maximum recommended PWM frequency is 1kHz. Frequencies above this may cause
noise in the audible range. THERMAL PROTECTION
When the junction temperature exceeds 150В°C (typ.), internal thermal protection circuitry disables the device.
This feature protects the LM2751 from damage due to excessive power dissipation. The device will recover and
operate normally when the junction temperature falls below 140В°C (typ.). It is important to have good thermal
conduction with a proper layout to reduce thermal resistance. POWER EFFICIENCY
Charge-Pump efficiency is derived in the following two ideal equations (supply current and other losses are
neglected for simplicity):
IIN = G x IOUT
E = (VOUT x IOUT) Г (VIN x IIN) = VOUT Г (G x VIN) (4)
(5) In the equations, G represents the charge pump gain. Efficiency is at its highest as G x VIN approaches VOUT.
Refer to the efficiency graph in the Typical Performance Characteristics for the detailed efficiency data. POWER DISSIPATION …
