LTC1706-82 Linear Technology, LTC1706-82 Datasheet - Page 5

• Manufacturer Part Number: LTC1706-82
• Description: VID Voltage Programmer for Intel VRM 9.0
• Manufacturer: Linear Technology

BLOCK DIAGRA
OPERATIO
The LTC1706-82 is a precision resistive divider designed
specifically for use with an entire family of Linear Technol-
ogy Corporation DC/DC switching regulators with 0.8V
internal reference and feedback voltages. The LTC1706-82
produces an output voltage ranging from 1.10V to 1.85V
in 25mV steps by closing the loop between the output
voltage sense and the feedback input of the regulator with
the appropriate resistive divider network.
The “top” feedback resistor, R
SENSE and FB, is typically 10k and is not modified by the
state of the VID program inputs.
The “bottom” feedback resistor, R
fied by the five VID inputs and is precisely ratioed to R
VID0
VID1
VID2
VID3
1
2
3
4
U
V
V
V
V
CC
CC
CC
CC
40k
40k
40k
40k
W
FB1
FB2
, connected between
, however is modi-
VID4
7
V
FB1
CC
40k
.
VID Programming
A list of programmed inputs and their corresponding
output voltages is shown in Table 1. Programming is
accomplished by applying the proper voltage (or float
condition) on the five digital VID inputs. VID4 is the most
significant bit (MSB) and VID0 is the least significant bit
(LSB).
When the five VID inputs are low, or grounded, the
regulator output voltage is set to 1.85V. Each increasing
binary count is equivalent to a decrease of 25mV in the
output voltage. Therefore, to obtain a 1.10V output, only
VID0 is grounded while the other four VID inputs are tied
high or floating.
When all five VID inputs are high or floating, such as when
no CPU is present in a system, a regulated 1.075V output
is generated at V
CONTROL
SWITCH
LOGIC
V
CC
5
SENSE
.
R
10k
R
LTC1706-82
FB1
FB2
10
6
9
1706-82 BD
SENSE
FB
GND
5