CS5155H
condition ceases or the input voltage is pulled low. The
5.0 V
bottom FET and board trace must be properly designed to
implement the OVP function.
Shutdown
Input
MMUN2111T1 (SOT−23)
IN4148
5 SS
CS5155H
8 VFFB
M 10.0 μs
Trace 4− 5.0 V from PC Power Supply (5.0 V/div.)
Trace 1− Regulator Output Voltage (1.0 V/div.)
Trace 2− Inductor Switching Node 5.0 V/div.)
Figure 14. OVP Response to an Input−to−Output
Short Circuit by Immediately Providing 0% Duty
Cycle, Crow−Barring the Input Voltage to Ground
M 5.00 ms
Trace 4− 5.0 V from PC Power Supply (2.0 V/div.)
Trace 1− Regulator Output Voltage (1.0 V/div.)
Figure 15. OVP Response to an Input−to−Output Short
Circuit by Pulling the Input Voltage to Ground
External Output Enable Circuit
On/off control of the regulator can be implemented
through the addition of two additional discrete components
(see Figure 16). This circuit operates by pulling the Soft
Start pin high, and the VFFB pin low, emulating a short
circuit condition.
Figure 16. Implementing Shutdown with the CS5155H
External Power Good Circuit
An optional Power Good signal can be generated through
the use of four additional external components (see Figure
17). The threshold voltage of the Power Good signal can be
adjusted per the following equation:
VPower
Good
+
(R1
)
R2)
R2
0.65 V
This circuit provides an open collector output that drives
the Power Good output to ground for regulator voltages less
than VPower Good.
5.0 V
R1
10 k
VOUT
CS5155H
R3
10 k
PN3904
R2
6.2 k
Power Good
PN3904
Figure 17. Implementing Power Good with the CS5155H
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