LTC1699 Series
U
W
U U
APPLICATIO S I FOR ATIO
In general, adjustable DC/DC Converters regulate the
output voltage by dividing it down with a resistor divider
and comparing the result against a precision reference
voltage (VREF). As shown in the Block Diagram, the
LTC1699-80, LTC1699-81 and LTC1699-82 are variable
resistordividers, whichareprogrammedthrougha2-wire
SMBus interface. They are specifically designed to sim-
plify the implementation of a voltage regulator module
(VRM) in both portable and desktop computers.
Two 5-bit divider settings can be programmed into Regis-
ter 0 and Register 1 using the SMBus interface. The
microprocessor selects one of these settings using the
TTL compatible SEL pin to control a 10:5 multiplexer
(MUX).Theprecision±0.35%dividerisintendedtosetthe
Table 1. DC/DC Converter Output Voltage for VREF = 0.8V
VID0 LTC1699-80 LTC1699-81 LTC1699-82
VID4
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
VID3
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
VID2
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
0
0
0
0
1
1
1
1
VID1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
0
1
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
0
1
2.000V
1.950V
1.900V
1.850V
1.800V
1.750V
1.700V
1.650V
1.600V
1.550V
1.500V
1.450V
1.400V
1.350V
1.300V
1.250V
1.275V
1.250V
1.225V
1.200V
1.175V
1.150V
1.125V
1.100V
1.075V
1.050V
1.025V
1.000V
0.975V
0.950V
0.925V
0.900V
2.05V
2.00V
1.95V
1.90V
1.85V
1.80V
1.75V
1.70V
1.65V
1.60V
1.55V
1.50V
1.45V
1.40V
1.35V
1.30V
3.50V
3.40V
3.30V
3.20V
3.10V
3.00V
2.90V
2.80V
2.70V
2.60V
2.50V
2.40V
2.30V
2.20V
2.10V
2.00V
1.850V
1.825V
1.800V
1.775V
1.750V
1.725V
1.700V
1.675V
1.650V
1.625V
1.600V
1.575V
1.550V
1.525V
1.500V
1.475V
1.450V
1.425V
1.400V
1.375V
1.350V
1.325V
1.300V
1.275V
1.250V
1.225V
1.200V
1.175V
1.150V
1.125V
1.100V
1.075V
10
Linear [ Linear ]
