RT9174PS 查看數據表（PDF） - Richtek Technology

零件编号

产品描述 (功能)

生产厂家

RT9174PS

Triple Linear Regulator Controllers

Richtek Technology 

RT9174

Preliminary

Application Information

Capacitors Selection

A 0.1μF minimum capacitor is recommended between VDD

and ground to increase stability. The linear controllers use

dominant pole compensation integrated into the error

amplifier and are sensitive to output capacitor selection.

When driving external pass transistor, normally a minimum

470μF capacitor must be placed at output for stability and

good transient response. When using internal pass

transistor, just need 10μF capacitor for stable.

Pass Transistor Selection

The RT9174 are designed specifically to driver external

NPN or NMOSFET pass transistor for up to 5A output

current. The driver could deliver more 100mA when driving

NPN transistor and sinking for a pull up resistor load when

driving a NMOSFET.

Typically pass transistor with NPN hfe > 50 at Imax or

NMOSFET Rds-on 100mΩ are suitable in most

application.

Output Voltage Setting

The RT9174 develop a 0.8V reference voltage, especially

suit for low voltage application. As shown in Figure 4, the

output voltage could be easy set by R1 & R2 resistor.

The divided resistor must keep below 1kΩ for quick

response and stability.

Tri-state Operation

A special Tri-state design is empolyed in the RT9174 for

AGP 2X/4X power supply. Typical application shown the

detail circuit. In AGP 2X SELECT = open, FB1 will be

pulled up over 1.3V through R8 to trip the Tri-state

threshold. R8 has to meet the following relationship:

R8 < 0.75 (V33 - 1.3) x R2,

if R3 + R2 × 0.8 = 1.5 .

R3

When in AGP 4X SELECT = GND, VDDQ will work in

normal 1.5V setting.

Layout Considerations

There are two critical layout considerations. One is the

divider resistors should be located to RT9174 as possible

to avoid inducing any noise. The second is COUT should

be put at near the pass transistor to avoid oscillation.

VDD

1uF

DR11

VDD RT9174 DR12

DR13

FB1

FB2

R1

FB3

R2

As close as to RT9174

Figure 4

VIN

VOUT

COUT

www.richtek.com

6

DS9174-06 March 2007

Share Link: