A4403 データシートの表示（PDF） - Allegro MicroSystems
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A4403 Datasheet PDF : 15 Pages
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A4403
Valley Current Mode Control Buck Converter
Functional Block Diagram
VIN 9 to 44.1 V
R1
68 kΩ
C1
2.2 μF
R2
Not
Fitted
Sleep
Circuit
VIN
Linear
Regulator
TON
DIS
On
Timer
Off
Timer
Control
Logic
Switch
Closed = On
C2
22 nF
BOOT
Top-off VIN
Charge
Pump
LX
Driver
Blank
Overvoltage Reg Ref
Comparator +80 mV
ISEN
SGND
FB
VIN UVLO
Linear OK Fault
Regulator
Comparator
Amplifier
TSD
Soft-Start
Reg Ref
L1
4.7 μH
D1
C3
C4
10 μF 10 μF
R3
100 mΩ
R4
100 mΩ
C6
10 nF
VOUT
3.3 V
3A
R5
2.37 kΩ
R6
750 Ω
SS
C5
47 nF
NC
GND
Switching Frequency = 1 MHz
All capacitors are X5R or X7R ceramic
Resistors R3 and R4 should be surface mount, low inductance type, rated at 250 mW at 70°C
C6 is an optional speed-up capacitor, to improve the transient response
Pin-out Diagram
VIN 1
NC 2
TON 3
SS 4
PAD
12 LX
11 BOOT
10 DIS
9 SGND
(Top View)
Terminal List Table
Number
Name
Function
1
2, 7, 13, 14, 15, 16
3
4
5
6
8
VIN
NC
TON
SS
FB
GND
ISEN
Input supply
No connection; tie to GND
Terminal for on-time setting with external resistor
Terminal for soft-start setting with external capacitor
Feedback terminal
Ground terminal
Current sense input
9
SGND Current sense ground reference
10
DIS Disable logic input; active high
11
BOOT Bootstrap supply node
12
LX Switch node
–
PAD
Exposed thermal pad; connect to ground plane
(GND) by through-hole vias
Allegro MicroSystems, Inc.
3
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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