SI9912 Datasheet, PDF (6/8 Pages) Vishay Siliconix – Half-Bridge MOSFET Driver for Switching Power Supplies

Si9912
Vishay Siliconix
TYPICAL CHARACTERISTICS (25_C UNLESS NOTED)
V_OUT(H+) vs. Temperature
0
−1
0.5 A
V_OUT(H−) vs. Temperature
5
See Figure 3
4
−2
1A
−3
See Figure 3
−4
−5
−50 −25
0
25
50
Temperature (_C)
75
100
V_OUT(L+) vs. Temperature
0
0.5 A
−1
1A
−2
1.5 A
−3
−4
2A
See Figure 3
−5
−50 −25
0
25
50
75
100
Temperature (_C)
3
2A
2
1
0
−50 −25
0
25
50
Temperature (_C)
1.5 A
1A
0.5 A
75
100
V_OUT(L−) vs. Temperature
2.0
See Figure 3
1.5
2A
1.0
1.5 A
1A
0.5
0.5 A
0.0
−50 −25
0
25
50
Temperature (_C)
75
100
THEORY OF OPERATION
Break-Before-Make Function
The Si9912 has an internal break-before-make function to
ensure that both high-side and low-side MOSFETs are not
turned on at the same time. The high-side drive (OUT_H) will not
turn on until the low-side gate drive voltage (measured at the
OUT_L pin) is less than V_BBM, thus ensuring that the low-side
MOSFET is turned off. The low-side drive (OUT_L) will not turn
on until the voltage at the MOSFET half-bridge output
(measured at the V_S pin) is less than V_BBM, thus ensuring that
the high-side MOSFET is turned off.
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6
Under Voltage Lockout Function
The Si9912 has an internal under-voltage lockout feature to
prevent driving the MOSFET gates when the supply voltage (at
V_DD) is less than the under-voltage lockout specification
(V_UVL). This prevents the output MOSFETs from being turned
on without sufficient gate voltage to ensure they are fully on.
There is hysteresis included in this feature to prevent lockout
from cycling on and off.
Document Number: 71311
S-40134—Rev. B, 16-Feb-04