AME5138 Datasheet | Analog Microelectronics

.. AME, Inc. AME5138 n General Description The AME5138 is a fixed off-time step-up DC/DC converter in a small 5-lead SOT-25 package.The AME5138 is ideal for LCD panels requiring low current and high efficiency as well as LED applications for cellular phone backlighting, PDAs,and other hand-held devices. The low 400ns off-time allows the use of tiny external ponents. AME5138 is designed to drive up to four white LEDs in series with a constant current from a single Li-lon battery. To control LED brightness, the LED current can be adjusted by applying a PWM (pulse width modulated) signal with a frequency range of 100Hz to 50KHz to the EN pin. Micropower Step-Up DC/DC Converter n Typical Application V IN 2.5V-4.2V 5 V IN L 10µH 1 SW ILED COUT 1µF Ceramic D Option for 4LEDs CIN 4.7µF Ceramic >1.1V 4 EN 0V GND 2 FB 3 R2 80Ω - ILED =VFB/R2 n Features l 0.7Ω internal switch l Uses small surface mount ponents l Adjustable output voltage up to 20V l 2V to 5.5V input range l Input undervoltage lockout l 0.01µA shutdown current l Small 5-Lead SOT-25 package l All AME's lead free Product Meet Ro HS Standard Figure 1¡G Four White LEDs Application in Li-lon Battery VIN 2.5V-4.2V L 15µ H 20V 10m A 5 CIN 4.7µF Ceramic 4 VIN 1 SW 3 R1 200K AME5138 FB EN GND 2 COUT 1µF Ceramic R2 13K n Applications l l l l l White LED Back-Lighting Hand-held Devices Digital Cameras Portable Applications LCD Bias Power Figure 2¡G Typical 20V Application AME, Inc. AME5138 n Function Block Diagram L VIN CIN VIN SW D Micropower Step-Up DC/DC Converter VOUT COUT VOUT Vref=1.23 Enable p R1 + R2 400ns one...