AN727
Vishay Siliconix
Document Number: 70959
07-Jul-99
www.vishay.com FaxBack 408-970-5600
1
High-Frequency, High-Efficiency Buck Converter Design For
Multi-Cell Battery Configured Systems Using Si9167
Nitin Kalje
C0082
The Si9167 is a high-frequency synchronous dc-to-dc
switching buck regulator, with an operating range suitable for
two-cell Li+ battery-powered applications. Capable of
operation up to 2 MHz, the Si9167 can be used to supply
power amplifiers and to power up baseband circuits in satellite
phones. Its high operating frequency reduces the size of
inductor and capacitor components, while its low
on-resistance internal driver ensures maximum power
conversion efficiency. Additional features include an
integrated input undervoltage lockout, power on reset,
integrated soft start, light load pulse skipping mode selection,
synchronization, clock output for master-slave configuration of
multiple regulators, uncommitted power-good comparator,
and over temperature protection. An output power in excess of
2 W at 3.6 V
O
is possible in 0.3 square inches.
C0089C0080 C0080C0080 C0082
FIGURE 1. Typical Application Circuit—Buck
1
+V
IN
5 - 10 V
2
PGND
1
2
3
4
5
6
7
8
9
10
SD
PWM/PSM
V
IN
V
IN
POK
SYNC
CLK
GND
V
REF
FB
20
19
18
17
16
15
14
13
12
11
COIL
COIL
PGND
COIL
PGND
POKIN
V
O
V
DD
R
OSC
COMP
C1
10 F
16 V
C1
0.1 F
R9*
51 k
* Optional
C3
0.1 F
STAR GND CON
R3
8.2 k
C5
1000 pF
C4
56 pF
D1
R2
75 k
R1*
51
C6
0.1 F
L1
4.7 H
IHLP2525
R4
200
C7
330 pF
R5
22 k
R6
12.4 k
C1
10 F
16 V
C9
0.1 F
MBRO520T1
R8
64 k
R7
105 k
7
V
OUT
8
PGND
3.6 V @ 600 mA
1.3 V
Si9167
ENABLE/DISABLE
PWM/PSM