AME5136 Datasheet, PDF (7/15 Pages) Analog Microelectronics – Integrated White LED Driver With Organic LED Display Power Supply

AME, Inc.
AME5136
Integrated White LED Driver With
Organic LED Display Power Supply
n Detailed Description
The AME5136 is designed for white LED & OLED back-
lighting in mobile phone applications. It has a main dis-
play loop which can drive up to 4 white LEDS in series
and a SUB display loop which is designed to drive OLED
up to 20V/10mA or 3 white LEDs.
The AME5136 operates at a wide input voltage range
suitable for Li-ion battery and has a constant off time for
smaller inductor and capacitors. The block diagram re-
fers the operation circuit. By SEL pin, it can choose the
different channel to turn on CH1 or CH2.
Current Limit Protection
The AME5136 has current limiting protection to pre-
vent excessive stress on itself and external components
during overload conditions. The internal current limit com-
parator will disable the NMOS power device at a typical
switch peak current limit of 300mA.
Output Over-Voltage Protection
The AME5136 contains dedicated circuitry for monitor-
ing the output voltage. In the event that the primary LED
network is disconnected the output will increase and be
limited to 22V(typ.). There is a ~1V hysteresis associ-
ated with this circuitry, which will turn the NMOS off when
the output voltage is at 23V(max.) until the output volt-
age reach 21V(typ.) or lower. The 22V limit allows the
use of 25V 1µF ceramic output capacitors creating an
overall small solution for white LED applications.
Under Voltage Protection
The AME5136 has an UVP comparator to turn the NMOS
power device off in case the input voltage or battery volt-
age is too low preventing an on state of the power device
conducting large amounts of current.
n Application Information
Inductor Selection
The recommended value of inductor for AME5136 ap-
plications is 10uH. Small size and better efficiency are
the major concerns for portable device, such as AME5136
used for dual panel mobile phone. The inductor should
have low DCR for better efficiency. To avoid inductor satu-
ration, current rating should be at least 600mA. The in
put range is 2.7V to 5.5V.
Capacitor Selection
4.7µF input capacitor can reduce input ripple. For bet-
ter voltage stability, to increase the input capacitor value
or using LC filter is feasible, especially in the Li-ion bat-
tery application. 1uF output capacitor is sufficient to re-
duce output voltage ripple. For better voltage filtering,
ceramic capacitors with low ESR are recommended. X5R
and X7R types are suitable because of their wider voltage
and temperature ranges.
Diode Selection
Schottky diode is a good choice for AME5136 because
of its lower forward voltage drop and faster reverse recov-
ery. Using schottky diode can get better efficiency. The
high speed rectification is also a good characteristic of
schottky diode for high switching frequency. Current rat-
ing of the diode must meet the root mean square of the
peak current and output average current multiplication.
7