CS5156GD16 datasheet(10/14 Pages) CHERRY

10 / 14 page

Applications Information: continued

External Output Enable Circuit

On/off control of the regulator can be implemented

through two additional discrete components (see Figure 12).

This circuit operates by pulling the soft start pin high, and

the VFFB pin low, emulating a short circuit condition.

Figure 12: Implementing shutdown with the CS5156.

External Power Good Circuit

An optional Power Good signal can be generated through

the use of four additional external components (see Figure

15). The threshold voltage of the Power Good signal can be

adjusted per the following equation:

VPower Good =

This circuit provides an open collector output that drives

the Power Good output to ground for regulator voltages

less than VPower Good.

Figure 13: Implementing Power Good with the CS5156.

Figure 14: CS5156 demonstration board during power up. Power Good

signal is activated when output voltage reaches 1.70V.

Selecting External Components

The CS5156 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 12V supply

which is generally available in most computer systems and

use logic level MOSFETs. A charge pump may be easily

implemented to support 5V only systems. Multiple

MOSFETs may be paralleled to reduce losses and improve

efficiency and thermal management.

Voltage applied to the MOSFET gate depends on the appli-

cation circuit used. The gate driver output is specified to

drive to within 1.5V of ground when in the low state and to

within 2V of its bias supply when in the high state. In prac-

tice, the MOSFET gate will be driven rail to rail due to

overshoot caused by the capacitive load it presents to the

controller IC. For the typical application where VCC1 = VCC2

= 12V and 5V is used as the source for the regulator output

current, the following gate drive is provided;

VGATE = 12V - 5V = 7V (see Figure 15).

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

Trace 4 = 5V Input (2V/div.)

Trace 1 = Regulator Output Voltage (1V/div.)

Trace 2 = Power Good Signal (2V/div.)

VOUT

CS5156

10k

6.2k

10k

Power Good

PN3904

(R1 + R2) × 0.65V

Shutdown

Input

VFFB

CS5156

IN4148

MMUN2111T1 (SOT-23)

CS5156GD16 датащи(PDF) 10 Page - Cherry Semiconductor Corporation

CS5156GD16 датащи(HTML) 10 Page - Cherry Semiconductor Corporation

Html Pages

1 2 3 4 5 6 7 8 9 10 11 12 13 14

датащи скачать

ссылки URL