Sharp LC-22LE240E, Service Manual

Page: 45 / 88

45
LC-22LE240
12.5. Pinning
13. MP2012 (U176)
13.1. General Description
The MP2012 is a fully integrated, internally compensated 1.2MHz fixed frequency PWM
step-down converter. It is ideal for powering portable equipment that runs from a single
cell Lithium-Ion (Li+) Battery, with an input range from 2.7V to 6V. The MP2012 can
provide up to 1.5A of load current with output voltage as low as 0.8V. It can also operate
at 100% duty cycle for low dropout applications. With peak current mode control and
internal compensation, the MP2012 is stable with ceramic capacitors and small inductors.
Fault condition protection includes cycle-by-cycle current limiting and thermal shutdown.
13.2. Features
 2.7-6V Input Operation Range
 Output Adjustable from 0.8V to VIN

1μA Max Shutdown Current.
 Up to 95% Efficiency
 100% Duty Cycle for Low Dropout
 Applications
 1.2MHz Fixed Switching Frequency
 Stable with Low ESR Output Ceramic
 Capacitors
 Thermal Shutdown
 Cycle-by-Cycle Over Current Protection
 Short Circuit Protection
 Available in 6-pin 3x3mm QFN
13.3. Pinning
Pin
#
Name Description
1 FB Feedback input. An external resistor divider from
the output to GND, tapped to the FB pin sets the
output voltage.
2 GND,
Exposed
Pad
Ground pin. Connect exposed pad to ground
plane for proper thermal performance.
3 SW Switch node to the inductor.
4 PVIN Input supply pin for power FET.
5 VIN Input Supply pin for controller. Put small
decoupling ceramic near this pin.
6 EN Enable input, “High” enables MP2012. EN is
pulled to GND with 1Meg internal resistor.
14. RTA8283A (U23, U173)
14.1. General Description
The RT8283A is a high-efficiency, monolithic synchronous step-down DC/DC converter
that can deliver up to 3A output current from a 4.5V to 23V input supply. The RT8283A's
current mode architecture and external compensation allow the transient response to be
optimized over a wide range of loads and output capacitors. Cycle-by-cycle current limit
provides protection against shorted outputs and soft-start eliminates input current surge
during start-up. The RT8283A also provides output under voltage protection and thermal
shutdown protection. The low current (<3μA) shutdown mode provides output disconnect,
enabling easy power management in batterypowered systems. The RT8283A is available
in a SOP-8 package.
14.2. Features
 ±1.5% High Accuracy Feedback Voltage
 Integrated N-MOSFET Switches
 Current Mode Control
 Fixed Frequency Operation : 340kHz
 Output Adjustable from 0.8V to 20V
 Up to 95% Efficiency
 Thermal Shutdown Protection
14.3. Pinning