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1
LTC1706-81
APPLICATIO S
U
FEATURES
DESCRIPTIO
U
TYPICAL APPLICATIO
N
U
5-Bit VID-Controlled High Current 4-Phase Application (Simplified Block Diagram)
5-Bit Desktop VID
Voltage Programmer
s
Programs Regulator Output Voltage Range from
1.3V to 2.05V in 50mV Steps and from 2.1V to 3.5V
in 100mV Steps (VRM 8.4)
s
Programs a Wide Range of Linear Technology
DC/DC Converters with a 0.8V Reference
s
Fully Compliant with the Intel Pentium
Processor
Desktop VID Specification
s
0.25% Accurate Output Voltage
s
Built-In 40k Pull-Up Resistors on VID Inputs
s
Available in MSOP-10 Package
The LTC
1706-81 is a precision, digitally programmed,
resistive ladder which adjusts the output of any 0.8V
referenced regulator. Depending on the state of the five
VID inputs, an output voltage between 1.3V and 3.5V is
programmed in 50mV and 100mV increments.
The LTC1706-81 is designed specifically to program
an entire family of Linear Technology DC/DC converters in
full compliance with the Intel Desktop (VRM 8.4) VID
specification.
The LTC1706-81 programs the following Linear
Technology DC/DC converter products: LTC1622,
LTC1628, LTC1629, LTC1702, LTC1735, LTC1735-1,
LTC1772 and LTC1929. (Consult factory for future com-
patible DC/DC converter products.)
s
Intel Pentium
II and III Processor Power Supply
s
AMD Athlon
TM
Processor Power Supply
s
Workstations and Servers
s
Large Memory Array Supply
1706-81 TA01
L1
R
SENSE1
V
IN
V
IN
4.5V TO 22V
V
IN
4.5V TO 22V
LTC1629
INTV
CC
V
DIFFOUT
SGND
EAIN
C
OUT
V
IN
TG1
SW1
BG1
PGND
+
V
OUT
1.3V TO 3.5V
UP TO 70A
VID0
VID1
VID2
VID3
VID4
V
CC
LTC1706-81
GND
SENSE
FB
FROM
P
L2
R
SENSE2
L3
R
SENSE3
V
IN
LTC1629
SGND
EAIN
V
IN
TG1
SW1
BG1
PGND
L4
R
SENSE4
TG2
SW2
BG2
TG2
SW2
BG2
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
AMD Athlon is a trademark of Advanced Micro Devices, Inc.
2
LTC1706-81
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: The LTC1706-81 is guaranteed to meet performance specifications
from 0
C to 70
C. Specifications over the 40
C to 85
C operating
temperature range are assured by design, characterization and correlation
with statistical process controls.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Operating Supply Voltage Range
2.7
5.5
V
I
VCC
Supply Current
(Note 3)
0.1
5
A
R
FB-SENSE
Resistance Between SENSE and FB
q
12
20
28
k
V
OUT
Error %
Output Voltage Accuracy
Programmed from 1.3V to 2.05V (VID4 = 0)
q
0.25
+ 0.25
%
Programmed from 2.1V to 3.5V (VID4 = 1)
q
0.35
+ 0.25
%
R
PULLUP
VID Input Pull-Up Resistance
V
DIODE
= 0.6V (Note 4)
40
k
VID
TH
VID Input Voltage Threshold
V
IL
(2.7V
V
CC
5.5V)
0.4
V
V
IH
(2.7V
V
CC
5.5V)
1.6
V
I
VID-LEAK
VID Input Leakage Current
V
CC
< VID < 7V (Note 4)
0.01
1
A
V
PULLUP
VID Pull-Up Voltage
V
CC
= 3.3V
2.8
V
V
CC
= 5V
4.5
V
LTC1706EMS-81
T
JMAX
= 110
C,
JA
= 120
C/ W
(Note 1)
ABSOLUTE
M
AXI
M
U
M
RATINGS
W
W
W
U
PACKAGE/ORDER I
N
FOR
M
ATIO
N
W
U
U
ELECTRICAL CHARACTERISTICS
Consult factory for Industrial and Military grade parts.
The
q
denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25
C.
2.7V
V
CC
5.5V, VID0 = VID1 = VID2 = VID3 = VID4 = NC unless otherwise specified.
(Voltages Referred to GND Pin)
Input Supply Voltage (V
CC
) .......................... 0.3V to 7V
VID Input Pins ............................................. 0.3V to 7V
SENSE Pin ................................................... 0.3V to 7V
FB Pin .......................................................... 0.3V to 7V
Operating Temperature Range (Note 2) .. 40
C to 85
C
Junction Temperature ........................................... 110
C
Storage Temperature Range ................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
1
2
3
4
5
VID0
VID1
VID2
VID3
V
CC
10
9
8
7
6
FB
GND
NC
VID4
SENSE
TOP VIEW
MS10 PACKAGE
10-LEAD PLASTIC MSOP
ORDER PART
NUMBER
MS10
PART MARKING
LTLR
Note 3: With all five VID inputs floating, the V
CC
supply current is simply
the device leakage current. However, the V
CC
supply current will rise and
be approximately equal to the number of grounded VID input pins times
(V
CC
0.6V)/40k. (See the VID Input Characteristics section for more
details.)
Note 4: Each built-in pull-up resistor attached to the VID inputs also has a
series diode connected to V
CC
to allow input voltages higher than the V
CC
supply without damage or clamping. (See Operation section for further
details.)
3
LTC1706-81
TYPICAL PERFOR
M
A
N
CE CHARACTERISTICS
U
W
OUTPUT VOLTAGE (V)
1.3
ERROR (%)
1706-81 G01
0.25
0
0.25
1.5 1.7 1.9 2.1 2.3 2.5 2.7 2.9 3.1 3.3 3.5
T
A
= 25
C
VID4 = 0
VID4 = 1
TEMPERATURE (
C)
50
0
50
100
ERROR (%)
1706-81 G02
0.25
0
0.25
V
OUT
= 2V
V
OUT
= 1.7V
V
OUT
= 1.3V
V
OUT
= 3.5V
Typical Error % vs Output Voltage
Typical Error % vs Temperature
TEMPERATURE (
C)
50
0
50
100
R
FB1
(k
)
1706-81 G03
30
20
10
0
TEMPERATURE (
C)
50
0
50
100
VID PULL-UP CURRENT (
A)
1706-81 G04
120
100
80
60
40
20
0
V
CC
= 5V
VID4 = 0V
VID0 = VID1 = VID2 = VID3 = OPEN
R
FB1
vs Temperature
I
VID-PULLUP
vs Temperature
TEMPERATURE (
C)
50
0
50
100
SUPPLY CURRENT (
A)
1706-81 G05
2.0
1.5
1.0
0.5
0
V
CC
= 2.7V
V
CC
= 5V
ALL VID INPUTS OPEN
V
CC
= 3.3V
SUPPLY VOLTAGE (V)
0
2
4
6
8
SUPPLY CURRENT (
A)
1706-81 G06
5
4
3
2
1
0
ALL VID INPUTS OPEN
T
A
= 25
C
Supply Current vs Temperature
Supply Current vs Supply Voltage
4
LTC1706-81
VID0 (Pin 1): LSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID0 adds 50mV
(VID4 = LOW) or 100mV (VID4 = HIGH) to the output
sense voltage.
VID1 (Pin 2): 3rd MSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID1 adds 100mV
(VID4 = LOW) or 200mV (VID4 = HIGH) to the output
sense voltage.
VID2 (Pin 3): 2nd MSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID2 adds 200mV
(VID4 = LOW) or 400mV (VID4 = HIGH) to the output
sense voltage.
VID3 (Pin 4): MSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID3 adds 400mV
(VID4 = LOW) or 800mV (VID4 = HIGH) to the output
sense voltage.
V
CC
(Pin 5): Power Supply Voltage. Range from 2.7V to
5.5V.
SENSE (Pin 6): Regulator Output Voltage. Connect
directly to regulator output sense node or, when used with
the LTC1629 and LTC1929 to V
DIFFOUT
.
VID4 (Pin 7): High-Low Output Range Programming
Input. VID4 = Low puts the output voltage in the lower
range of 1.3V to 2.05V in 50mV steps. VID4 = HIGH puts
the output voltage in the upper range of 2.1V to 3.5V in
100mV steps.
NC (Pin 8): No Connect.
GND (Pin 9): Ground. Connect to regulator signal ground.
FB (Pin 10): Feedback Input. Connect to the 0.8V feedback
pin of a compatible regulator or the EAIN pin of the
LTC1629 and LTC1929.
NOMINAL (V)
ABSOLUTE MAX (V)
PIN
NAME
DESCRIPTION
MIN
TYP
MAX
MIN
MAX
1
VID0
LSB Programmable Input
0
V
CC
0.3
7
2
VID1
3rd MSB Programmable Input
0
V
CC
0.3
7
3
VID2
2nd MSB Programmable Input
0
V
CC
0.3
7
4
VID3
1st MSB Programmable Input
0
V
CC
0.3
7
5
V
CC
Power Supply
2.7
5.5
0.3
7
6
SENSE
Regulator Output Voltage
1.3
3.5
0.3
7
7
VID4
Output Range Programmable Input
0
V
CC
0.3
7
8
NC
9
GND
Ground
0
0.3
7
10
FB
0.8V Feedback Input
0
0.8
1.5
0.3
7
PI
N
FU
N
CTIO
N
S
U
U
U
5
LTC1706-81
BLOCK DIAGRA
W
1706-81 BD
40k
VID3
V
CC
40k
VID4
V
CC
40k
VID2
V
CC
40k
VID1
V
CC
40k
VID0
V
CC
R
FB2
R
FB1
SENSE
FB
GND
V
CC
1
2
3
4
6
5
10
9
7
SWITCH
CONTROL
LOGIC
OPERATIO
U
The LTC1706-81 is a precision resistive divider designed
specifically for use with an entire family of Linear
Technology Corporation DC/DC switching regulators with
0.8V internal reference and feedback voltage. The
LTC1706-81 produces an output voltage ranging from
1.3V to 2.05V in 50mV steps and from 2.1V to 3.5V in
100mV 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
FB1
, connected between
SENSE and FB, is typically 20k and is not modified by the
state of the VID program inputs.
The "bottom" feedback resistor, R
FB2
, however, is modi-
fied by the five VID inputs and is precisely ratioed to R
FB1
.
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 range
bit that puts the output voltage in either the 1.3V to 2.05V
range or the 2.1V to 3.5V range. In either range, VID3 is the
most significant bit (MSB) and VID0 is the least significant
bit (LSB).
In the lower range (VID4 = 0), when the four VID inputs are
low or grounded, the regulator output voltage is set to
2.05V. Each increasing binary count is equivalent to a
decrease of 50mV in the output voltage. Therefore, to
obtain a 1.3V output, the four VID inputs should be
floating, or high.
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