cs5157h ON Semiconductor, cs5157h Datasheet - Page 11

• Manufacturer Part Number: cs5157h
• Description: Cpu 5-bit Synchronous Buck Controller
• Manufacturer: ON Semiconductor

External Output Enable Circuit
through the addition of two additional discrete components
(see Figure 16). This circuit operates by pulling the
Soft−Start pin high, and the V
circuit condition.
External Power Good Circuit
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:
the Power Good output to ground for regulator voltages less
than V
Figure 15. OVP Response to an Input−to−Output Short
Figure 16. Implementing Shutdown with the CS5157H
On/off control of the regulator can be implemented
An optional Power Good signal can be generated through
This circuit provides an open collector output that drives
Trace 4− 5.0 V from PC Power Supply (2.0 V/div.)
Trace 1− Regulator Output Voltage (1.0 V/div.)
Shutdown
Circuit by Pulling the Input Voltage to Ground
Power Good
Input
V Power Good +
.
IN4148
5.0 V
M 5.00 ms
(R1 ) R2)
MMUN2111T1 (SOT−23)
FFB
pin low, emulating a short
5
8 V
R2
SS
FFB
CS5157H
0.65 V
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CS5157H
11
Selecting External Components
power components to optimize the cost and performance of
a particular design. The following information can be used
as general guidelines to assist in their selection.
NFET Power Transistors
reference designs derive gate drive from the 12 V supply
which is generally available in most computer systems and
utilize logic level MOSFETs. Multiple MOSFETs may be
paralleled to reduce losses and improve efficiency and
thermal management.
application circuit used. Both upper and lower gate driver
outputs are specified to drive to within 1.5 V of ground when
in the low state and to within 2.0 V of their respective bias
supplies when in the high state. In practice, the MOSFET
gates will be driven rail to rail due to overshoot caused by the
Figure 17. Implementing Power Good with the CS5157H
Trace 3 − 12 V Input (V
Trace 4− 5.0 V Input (2.0 V/div.)
Trace 1− Regulator Output Voltage (1.0 V/div.)
Trace 2− Power Good Signal (2.0 V/div.)
The CS5157H can be used with a wide range of external
Both logic level and standard MOSFETs can be used. The
Voltage applied to the MOSFET gates depends on the
Figure 18. CS5157H Demonstration Board During
Power Up. Power Good Signal is Activated when
CS5157H
V
OUT
Output Voltage Reaches 1.70 V.
10 k
CC1
R1
) and (V
M 2.50 ms
6.2 k
CC2
R2
) (10 V/div.)
5.0 V
PN3904
10 k
R3
PN3904
Power Good