SI9150 Datasheet, PDF (5/5 Pages) Vishay Siliconix – Synchronous Buck Converter Controller

Si9150
Vishay Siliconix
Pin 9: C_T
A capacitor from this pin to ground is charged until it reaches
2.5 V, at which point the capacitor is rapidly discharged. The
resulting sawtooth with about 1 V added is compared to the
input voltage at COMP to determine whether P-GATE and
N-GATE should be high or low. The maximum recommended
value for C_OSC is 200 pF (See Typical Characteristics). The
capacitor’s charging current is controlled by Pin 10, R_T.
Pin 10: R_T
The IC applies 2.5 V to this pin, and the current is mirrored and
applied to Pin 9 while charging the capacitor. The minimum
recommended value of R_OSC is 20 kW (Figure 1).
Pin 11: GND
Since the Si9150 has a high-side current limit, it is important
that V_DD track the voltage on the source of the p-channel
power MOSFET. For noise immunity, it is best to separate the
logic ground from the power ground. The logic ground should
be decoupled to V_DD through at least a 1-mF capacitor. The two
grounds may be connected by a path that is long compared to
the the path from V_DD to the source of the application’s
p-channel MOSFET.
Pin 12: N-GATE
This pin is used to drive the application’s n-channel MOSFET.
When turning the n-channel MOSFET off, the p-channel
MOSFET will not be turned on until N-GATE is within a few volts
of ground. This pin is low while either EN or STBY is low.
Pin 13: P-GATE
This pin is used to drive the application’s p-channel MOSFET.
The break before make circuitry for the P-GATE is
complimentary to that for the N-GATE. This pin is high while
either EN or STBY is low.
Pin 14: V_DD
This pin powers the IC. The connection between this pin and
the source of the p-channel FET should be as short as
practical. Read Pin 11’s description for bypassing
suggestions.
APPLICATIONS
V_IN
47 pF
0.039 mF
220 pF
3.32 kW
5600 pF
1 mF
100 mF
(20 V)
Si9943
1
14
2
13
3
12
10MQ060
4
Si9150 ₁₁
56.2 kW
5
10
200 pF
V_IN
6
9
33 pF
7
8
1 kW
43 mH
33.2 kW
14.7 kW
1000 pF
100 mF
+5 V
33.2 kW
Document Number: 70020
S-40752—Rev. F, 19-Apr-04
FIGURE 1. Typical Application Circuit
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