A4403 Datasheet, PDF (1/15 Pages) Allegro MicroSystems – Valley Current Mode Control Buck Converter

A4403
Valley Current Mode Control Buck Converter
Features and Benefits
▪ Extremely fast load-transient response with minimal
output voltage delta
▪ Achieves high step-down ratios with on-times < 50 ns
▪ User-configurable on-time, achieving switching
frequencies up to 2 MHz
▪ Minimal external components required
▪ Optimized for low value filter capacitors and inductors
▪ Wide input voltage range: 9 to 46 V
▪ Output Current: 3 A
▪ Low standby current <100 μA
▪ Supplied in thermally-enhanced QFN package
Applications:
▪ Printers, scanners
▪ Cable, DSL modems/routers
▪ Network and telecom
▪ Industrial control
▪ Distributed power systems
▪ Set top box
▪ High power LED supply
▪ Battery chargers
▪ GPS / Infotainment
Package 16-contact QFN (suffix EU):
4 mm × 4 mm × 0.75 mm
Description
The A4403 is a buck converter that uses valley current-mode
control. This control scheme allows very short switch on-times
to be achieved, making it ideal for applications that require
high switching frequencies combined with high input voltages
and low output voltages.
Low cost is accomplished through high switching frequencies
of up to 2 MHz, allowing smaller and lower value inductors
and capacitors. In addition, minimal external components are
required through high levels of integration. Optimal drive
circuits are utilized to minimize switching losses.
The switching frequency is maintained constant, as the on-time
is modulated by the input voltage. This feed-forward control
ensures excellent line correction. The on-time is set by an
external resistor pulled-up to the input supply.
When power is initially applied and the device is enabled, a
user-configurable soft-start function occurs to minimize inrush
current and to prevent output overshoot. Internal housekeeping
and bootstrap supplies are provided which only require the
addition of one small ceramic capacitor. A top-off charge pump
is also provide to ensure correct operation at light loads.
Internal diagnostics provide comprehensive protection against
overcurrents, input undervoltages, and overtemperatures.
The device package is a 16-contact, 4 mm × 4 mm, 0.75 mm
nominal overall height QFN, with exposed pad for enhanced
thermal dissipation. It is lead (Pb) free, with 100% matte tin
leadframe plating.
V_IN
9 to 46 V
R1
100 kΩ
C1
2.2 μF
100 V
C5
47 nF
Typical Application Diagram
VIN
BOOT
LX
A 4403
TON
ISEN
DIS
C2
22 nF
L1
6.3 μH
R3
50 mΩ
D1
C3
10 μF
6.3 V
SGND
SS
FB
GND
V_OUT
5.0 V
3A
C4
10 μF
6.3 V
R5
3.92 kΩ
R6
750 Ω
90.00
85.00
80.00
Efficiency versus Output Current
V_IN = 42 V
5V
3.3 V
75.00
70.00
65.00
60.00
0
1
2
3
Output Current (A)
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
4403-DS, Rev. 1