SMM105

Preliminary Information

Summit Microelectronics, Inc

2068 1.8 09/20/05

11

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

C5

0.02uF

R6 10K

C1 1uF

START

R7 10K

R5

20k

C7

0.01uF

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.

J1

1

2

3

4

5

6

7

8

9

10

Gnd

SCL

Gnd3

SDA

Rsrv5

MR

+10V

Rsrv8

+5V

Rsrv10

START

U1

SMM105

1

2

3

4

5

6

8

10

11

12

14

18

19

20

28

SCL

A2

START

A1

READY

A0

WP#

FILT_CAP

FAULT#

COMP2

VM

TRIM_CAP

COMP1

TRIM

SDA

R3

RTRIM

FAULT#

D1

DIODE

READY

VOUT

SMX3200 I2C Programming

Connector 10 pin Header

R1 and R2 need only be

placed once on the I2C bus

C4

0.1uF

R1 10K

R2 10K

R8 10K

C8

0.1uF

U2

Switching Regulator

+Vout

+Vin

VADJ (VREF)

PGOOD

The SMM105 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

R4

RSET1

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

Figure 7 – SMM105 Applications schematic for an adjustable switching regulator (Full regulator circuit not

shown).

APPLICATIONS INFORMATION (CONTINUED)