CS5157H データシートの表示（PDF） - ON Semiconductor

部品番号

コンポーネント説明

メーカー

CS5157H

CPU 5−Bit Synchronous Buck Controller

ON Semiconductor 

CS5157H

5.0 V

R1

10 k

VOUT

CS5157H

R3

10 k

PN3904

R2

6.2 k

Power Good

PN3904

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.

5.0 V

Shutdown

Input

MMUN2111T1 (SOT−23)

IN4148

5 SS

CS5157H

8 VFFB

Figure 16. Implementing Shutdown with the CS5157H

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.

Figure 17. Implementing Power Good with the CS5157H

M 2.50 ms

Trace 3 − 12 V Input (VCC1) and (VCC2) (10 V/div.)

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.)

Figure 18. CS5157H Demonstration Board During

Power Up. Power Good Signal is Activated when

Output Voltage Reaches 1.70 V.

Selecting External Components

The CS5157H can be used with a wide range of external

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

Both logic level and standard MOSFETs can be used. The

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.

Voltage applied to the MOSFET gates depends on the

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

http://onsemi.com

11

Share Link: