AS1364
Datasheet - Detailed Description
8 Detailed Description
The AS1364 output voltage is factory-trimmed or is adjustable from +1.2 to +5V, and is guaranteed to supply 1A of out-
put current. The device consists of a +1.20V internal reference, error amplifier, MOSFET driver, P-channel pass tran-
sistor, internal feedback voltage-divider and a comparator (see Figure 16).
Figure 16. AS1364 - Block Diagram
VIN
2.0V to 5.5V
4
IN
3
CIN
4.7µF
Thermal
Sensor
IN
MOSFET
Driver
w/ILIM
5
OUT
6
VOUT
1.2V to 5.0V
2
Shutdown
Logic
OUT
On
Off
COUT
4.7µF
EN
1.20V
Reference
VOUT Logic
Supply Voltage
+
–
Error
Amplifier
R1
RPOK
100kΩ
1
7
To Controller
POK
SET/BYP
+
–
+
–
R2
+
–
+
–
94%VREF
100mV
AS1364
8
GND
The +1.20V reference is connected to the inverting input of the error amplifier, which compares this reference with the
selected feedback voltage and amplifies the difference.
The MOSFET driver reads the error signal and applies the appropriate drive to the P-channel transistor. If the feedback
voltage is lower than the reference, the pass transistor gate is pulled lower, allowing more current to pass increasing
the output voltage. If the feedback voltage is too high, the pass transistor gate is pulled up, allowing less current to
pass to the output.
The low VOUT comparator senses when the feedback voltage has dropped 6% below its expected level, causing POK
to go low.
The output voltage is fed back through either an internal resistor-divider connected to OUT or an external resistor net-
work connected to SET. The comparator examines VSET/BYP and selects the feedback path. If VSET/BYP is below
50mV, the internal feedback path is used and the output is regulated to the factory-preset voltage.
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