SMM205
Preliminary Information
APPLICATIONS INFORMATION (CONTINUED)
+12VIN (+10V to +15V)
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
C4
C7
0.1uF
0.01uF
C8
RTRIMmax should be < the calculated value
0.1uF
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
R6 10K
R7 10K
R8 10K
C1 1uF
U3
START
READY
FAULT#
3
5
18
20
14
RTRIM
R3
START
READY
FAULT#
TRIM_CAPA
TRIMA
VOUT
11
VMA
U2 Switching Regulator
17
16
15
R4
RSET1
VMB
TRIMB
R2 10K
R1 10K
1
28
6
SCL
SDA
A0
TRIM_CAPB
+Vin
+Vout
10
SMM205 FILT_CAP
4
A1
A2
PGOOD
2
19
12
COMP1
COMP2
VADJ (VREF)
C5
0.02uF
8
R5
D1
WP#
20k
DIODE
START
J1
1
3
5
7
9
2
Gnd
SCL
SDA
MR
4
Gnd3
Rsrv5
6
8
+10V Rsrv8
+5V Rsrv10
10
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
SMX3200 I2C Programming
Connector 10 pin Header
R1 and R2 need only be
placed once on the I2C bus
Figure 7 – SMM205 Applications schematic for an adjustable switching regulator (Full regulator circuit not
shown).
Summit Microelectronics, Inc
2069 1.4 6/23/03
11