SMM205

Preliminary Information

Summit Microelectronics, Inc

2069 1.4 6/23/03

11

For Example:

If Vout=3.3V, R4=63.4K, 15% of Vout=0.5V

ITRIM=8uA, RTRIM=62.5K

Therefore Rtrim standard 1% value down

from 62.5K

C8

0.1uF

U3

SMM205

1

2

3

4

5

6

8

10

11

12

14

15

16

17

18

19

20

28

SCL

A2

START

A1

READY

A0

WP#

FILT_CAP

FAULT#

COMP2

VMA

TRIM_CAPB

TRIMB

VMB

TRIM_CAPA

COMP1

TRIMA

SDA

+12VIN (+10V to +15V)

START

R6 10K

C5

0.02uF

J1

1

2

3

4

5

6

7

8

9

10

Gnd

SCL

Gnd3

SDA

Rsrv5

MR

+10V

Rsrv8

+5V

Rsrv10

D1

DIODE

FAULT#

C4

0.1uF

R2 10K

START

R7 10K

READY

The SMM205 START pin must be inactive during power-up so

that the TRIM pin is high impedence. Once power is nominal,

the START pin can be active to start margin and ADOC

functions

C1 1uF

U2

Switching Regulator

+Vout

+Vin

VADJ (VREF)

PGOOD

R5

20k

RTRIM(R3) is calculated as follows:

VTRIMlow=0.3V, Regulator VREF=0.8V

The current through R3 is ITRIM=(0.8-0.3)/RTRIM

(ITRIM)(R4) > 15% of VOUT

RTRIMmax should be < the calculated value

R4

RSET1

C7

0.01uF

R3

RTRIM

R1 10K

R8 10K

SMX3200 I2C Programming

Connector 10 pin Header

R1 and R2 need only be

placed once on the I2C bus

VOUT

Figure 7 – SMM205 Applications schematic for an adjustable switching regulator (Full regulator circuit not

shown).

APPLICATIONS INFORMATION (CONTINUED)