RT9173B datasheet(10/13 Pages) RICHTEK

10 / 13 page

RT9173B

DS9173B-09 March 2007

www.richtek.com

General Regulator

The RT9173B could also serves as a general linear

regulator. The RT9173B accepts an external reference

voltage at REFENpin and provides output voltage regulated

to this reference voltage as shown in Figure 6, where

VOUT = VREF x R1/(R1+R2)

RDS(ON) vs. Temperature

0.23

0.25

0.27

0.29

0.31

0.33

0.35

0.37

0.39

0.41

0.43

0.45

-50

-25

100

125

Temperature (

°C)

SOP-8

VCNTL = 3.3V

Internal parasitic diode

Avoid forward-bias internal parasitic diode, VOUT to VCNTL,

and VOUT to VIN, the VOUT should not be forced some

voltage respect to ground on this pin while the VCNTL or

VIN is disappeared.

Consideration while designs the resistance of voltage

divider

Make sure the sinking current capability of pull-downNMOS

if the lower resistance was chosen so that the voltage on

VREFEN is below 0.2V.

In addition, the capacitor and voltage divider form the low-

pass filter. There are two reasons doing this design; one is

for output voltage soft-start while another is for noise

immunity.

How to reduce power dissipation on Notebook PC or

the dual channel DDR SDRAM application?

In notebook application, using RichTek’ s Patent

“

Distributed Bus Terminator Topology” with choosing

RichTek

’ s product is encouraged.

VCNTL

REFEN

GND

VIN

VOUT

RT9173B

REFEN

Make sure that VCNTL >= VIN in all conditions including

power on and off. As other linear regulator, dropout voltage

and thermal issue should be specially considered. Figure

6 and 7 show the RDS(ON) over temperature of RT9173B in

SOP-8 and TO-252 packages respectively. The minimum

dropout voltage could be obtained by the product of RDS(ON)

and output current. For thermal consideration, please refer

to the relative sections.

RDS(ON) vs. Temperature

0.24

0.27

0.30

0.33

0.36

0.39

0.42

0.45

0.48

-50

-25

100

125

Temperature (

°C)

TO-252

VCNTL = 3.3V

Application Information

Distributed Bus Terminating Topology

R(N+1)

RT9173B

VOUT

REFEN

BUS(0)

BUS(1)

BUS(2)

BUS(3)

BUS(4)

BUS(5)

BUS(6)

BUS(7)

BUS(8)

BUS(9)

BUS(N)

BUS(N+1)

Terminator Resistor

Figure 6

RT9173B Datasheet(PDF) 10 Page - Richtek Technology Corporation

RT9173B Datasheet(HTML) 10 Page - Richtek Technology Corporation

Html Pages

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

Datasheet Download

Link URL