Sharp LC-32LE140E, Service Manual

Page: 46 / 88

46
LC-32LE140
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.
1
4
. RTA8283A (U23, U173)
1
4
.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.
1
4
.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
1
4
.3. Pinning
Pin No. Pin
Name
Description
1 BOOT
Bootstrap for high-side gate driver. Connect a 0.1
μ
F or
greater ceramic capacitor from BOOT to SW pins.
2 VIN Input Supply 4.5V to 23V. Must bypass with a suitably
large ceramic capacitor.
3 SW Phase Node--Connect to external L-C filter..
4, 9 (Exposed
Pad)
GND Ground.
5 FB Feedback Input pin is connected to the converter output.
It is used to set the output of the converter to regulate to
the desired value via an internal res divider. For an
adjustable output, an external res divider is connected to
this pin.
6 COMP Compensation Node. COMP is used to compensate the
regulation Control loop. Connect a series RC network
from COMP to GND. In some cases, an additional
capacitor from COMP to GND is required.
7 EN Enable Input Pin. Logic high enables the converter; a
logic low forces the RT8253A into shutdown mode.
Attach this pin to VIN with a 100kΩ pull up resistor for
automatic startup.
8 SS Soft-Start Control Input. SS controls the soft-start period.
Connect a capacitor from SS to GND to set the soft-start
period. A 0.1
μ F capacitor sets the soft-start period to
13.5ms.
1
5
. MP1583 (U174)
1
5
.1. General Description
The MP1583 is a step-down regulator with a built-in internal Power MOSFET. It achieves
3A of continuous output current over a wide input supply range with excellent load and
line regulation. Current mode operation provides fast transient response and eases loop
stabilization. Fault condition protection includes cycle-by-cycle current limiting and thermal
shutdown. An adjustable soft-start reduces the stress on the input source at start-up. The
MP1583 requires a minimum number of external components, providing a compact
solution.
1
5
.2. Features
 3A Output Current
 Programmable Soft-Start
 100mΩ Internal Power MOSFET Switch
 Stable with Low ESR Output Ceramic Capacitors
 Up to 95% Efficiency
 20μA Shutdown Mode
 Fixed 385KHz Frequency
 Thermal Shutdown
 Cycle-by-Cycle Over Current Protection
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.
1
4
. RTA8283A (U23, U173)
1
4
.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.
1
4
.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
1
4
.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.
1
4
. RTA8283A (U23, U173)
1
4
.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.
1
4
.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
1
4
.3. Pinning