SI9160 Datasheet, PDF (8/11 Pages) Vishay Siliconix – Controller for RF Power Amplifier Boost Converter

Si9160
Vishay Siliconix
OPERATION OF THE SI9160 BOOST CONVERTER
The Si9160 combined with optimized complementary
MOSFETs provides the ideal solution to small, high efficiency,
synchronous boost power conversion. Optimized for a 1-cell
lithium ion, or 3-cell to 4-cell Nickel metal hydride battery, it is
capable of switching at frequencies of up to 2 MHz. Combined
with the Si6801, a complimentary high-frequency MOSFET,
efficiencies of over 90% are easily achieved in a very small
area.
PWM Controller
The Si9160 implements a synchronous voltage mode PWM
control topology and is especially designed for battery power
conversion. Voltage-mode control results in the most efficient
power conversion solution. Figure 1 below illustrates a
schematic for a synchronous boost converter with an input
range of 2.7 V to 5 V which covers the range of 1-cell LiIon and
3-cell or 4-cell NiMH/NiCd battery input respectively, and an
output voltage of 6 V. Note the maximum input voltage is limited
to the output voltage for a boost converter.
The switching frequency is determined by an external
capacitor and resistor connected to C_osc and R_osc pins. The
graph on page 5 in the Typical Characteristics section shows
the typical C_osc and R_osc values for various switching
frequency. Si9160 oscillator frequency can be easily
synchronized to external frequency as long as external
switching frequency is higher than the internal oscillator
frequency. The synchronization circuit is a series resistor and
capacitor fed into the C_osc pin of the Si9160. The
synchronization pulse should be greater than 1.5 V in
amplitude and a near square wave pulsed clock. Figure 1
shows typical values for the synchronization components.
Startup
Designed to operate with single cell Lithium Ion battery
voltage, the Si9160 has an operating range of 2.7 V to 6.0 V.
During start-up, the device requires 3.0 V to guarantee proper
operation, although it will typically start up at less than 2.2 V.
Once powered, Si9160 will continue to operate until the
voltage at V_DD is 2.7 V; at this point, the battery is basically
dead. During start-up, power for the chip is provided by the
battery through schottky diode D1 to V_DD and V_S pins. Once
the converter is fully operating, supply power is provided by the
converter output through diode D2, which overrides the D1
diode. This self perpetuating method of powering further
improves the converter efficiency by utilizing higher gate drive
to lower the on-resistance loss of the MOSFET.
1-Cell
LiIon
SYNC
D1
LS4148
D2
LS4148
R5
100 k
C10
0.33 mF
C2
0.1 mF
R4
2.2 k
C3
0.1 mF
R3
2.2 k
R2, 270 W
C6 C4
22 pF 0.1
mF
R1
10 k
C5
0.1 mF
Si9160
1
16
2 ^VDD
V_{S 15}
NC
3
D_{R 14}
4 ^DMAX
D_{S 13}
COMP
5
P_{GND 12}
FB
6
UVLO_{SET 11}
NI
7
C_{OSC 10}
8 ^VREF
R_{OSC 9}
GND ENABLE
R6
12 k
C10
0.1 mF
C11
36 pF
ML ML
C1 C2
10 mF 10 mF
4.7 mH
1
2 ^D1
3 ^S1
4 ^S1
G1
8
D2 ₇
S2
S2 ⁶
G2 ⁵
Si6801
R9
100 W
R10
3.6 k
C8
5600 pF
R11
1.2 k
C9
0.1 mF
ML ML
C3 C4
10 mF 10 mF
Power
Amplifier
www.vishay.com
8
FIGURE 1. Si9160 Boost Converter
Document Number: 70029
S-40700—Rev. H, 19-Apr-04