AS1364
Datasheet - D e t a i l e d D e s c r i p t i o n
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
Figure 16. AS1364 - Block Diagram
V
IN
2.0V to 5.5V
C
IN
4.7µF
4
IN
3
IN
MOSFET
Driver
w/I
LIM
Thermal
Sensor
5
OUT
6
V
OUT
1.2V to 5.0V
C
OUT
4.7µF
+
R
POK
100k
Ω
Error
Amplifier
1
POK
+
–
+
–
+
–
100mV
+
–
8
GND
–
1.20V
Reference
R
1
On
Off
V
OUT
Logic
Supply Voltage
2
EN
Shutdown
Logic
OUT
To Controller
7
SET/BYP
R
2
AS1364
94%
VREF
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 V
OUT
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 V
SET/BYP
and selects the feedback path. If V
SET/BYP
is below
50mV, the internal feedback path is used and the output is regulated to the factory-preset voltage.
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