LTC1706-85
VID Voltage Programmer
for Intel VRM 8.5
FEATURES
s
s
DESCRIPTIO
s
s
s
s
Fully Compliant with the Intel VRM 8.5 VID
Specification
Programs Regulator Output Voltage from 1.05V to
1.825V in 25mV Steps
Programs an Entire Family of Linear Technology
DC/DC Converters with 0.8V References
±0.25%
Voltage Programming Accuracy
Built-In 40k Pull-Up Resistors on Program Inputs
Available in MSOP-10 Packaging
The LTC
®
1706-85 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 1.05V and 1.825V
is programmed in 25mV increments.
The LTC1706-85 is designed specifically to program an
entire family of Linear Technology DC/DC converters in full
compliance with the Intel Voltage Regulator Module (VRM)
8.5 specification.
The LTC1706-85 programs the following Linear Technol-
ogy DC/DC converter products: LTC1622, LTC1628,
LTC1629, LTC1702, LTC1735, LTC1735-1, LTC1772,
LTC1773, LTC1778, LTC1929, LTC3728 and LTC3729.
Consult factory for additional DC/DC converter products
compatible with the LTC1706-85.
, LTC and LT are registered trademarks of Linear Technology Corporation.
Pentium is a registered trademark of Intel Corporation.
APPLICATIO S
s
s
s
Server/Desktop Computers
Multiprocessor Workstations and Servers
Multiphase Processor Power Supply
TYPICAL APPLICATIO
VID Controlled High Current 4-Phase DC/DC Converter (Simplified Block Diagram)
V
IN
4.5V TO 22V
V
OS+
INTV
CC
VID25
VID0
FROM
µP
V
CC
SENSE
LTC1629
V
DIFFOUT
SGND
FB
GND
EAIN
I
TH
CLKOUT
TG2
SW2
BG2
V
IN
4.5V TO 22V
PLLIN
LTC1929
V
IN
TG1
SW1
BG1
PGND
SGND
EAIN
I
TH
NOTE: UP TO SIX LTC1629s/LTC1929s CAN BE PARALLELED
TO DELIVER AS MUCH AS 200A
TG2
SW2
BG2
1706-85 TA01
V
OS–
V
IN
TG1
SW1
BG1
PGND
V
IN
R
SENSE1
V
OUT
1.05V TO 1.825V
UP TO 80A
C
OUT
VID1 LTC1706-85
VID2
VID3
R
SENSE2
R
SENSE3
V
IN
R
SENSE4
U
+
170685f
U
U
1
LTC1706-85
ABSOLUTE
(Notes 1, 2)
AXI U RATI GS
PACKAGE/ORDER I FOR ATIO
TOP VIEW
VID25
VID0
VID1
VID2
V
CC
1
2
3
4
5
10
9
8
7
6
FB
GND
NC
VID3
SENSE
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 3) .. – 40°C to 85°C
Junction Temperature ........................................... 110°C
Storage Temperature Range ................. – 65°C to 150°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
LTC1706EMS-85
MS
PART MARKING
LTYQ
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 110°C,
θ
JA
= 200°C/W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T
A
= 25°C.
2.7V
≤
V
CC
≤
5.5V, VID25 = VID0 = VID1 = VID2 = VID3 = NC unless otherwise noted. (Note 3)
SYMBOL
V
CC
I
VCC
R
FB1
V
OUT(ERROR)
R
PULLUP
V
IH
V
IL
I
IN
PARAMETER
Operating Supply Voltage Range
Supply Current
Resistance Between SENSE and FB
Output Voltage Accuracy
Pull-Up Resistance on VID
Minimum High Level Input Voltage (VID Inputs)
Maximum Low Level Input Voltage (VID Inputs)
Input Leakage Current (VID Inputs)
1.050
≤
V
SENSE
≤
1.825V
V
DIODE
= 0.6V (Note 5)
V
CC
= 3.3V
V
CC
= 3.3V
V
CC
< VID < 7V (Note 5)
0.01
(Note 4)
q
q
CONDITIONS
MIN
2.7
TYP
1
MAX
5.5
10
14
0.25
56
0.8
±1
UNITS
V
µA
kΩ
%
kΩ
V
V
µA
6
– 0.25
28
2
10
40
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
All voltages are with respect to GND pin.
Note 3:
The LTC1706-85 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.
Note 4:
Supply current is specified with all VID inputs floating. Due to the
internal pull-ups on the VID pins, the supply current will increase
depending on the number of grounded VID lines. Each grounded VID line
will draw approximately [(V
CC
– 0.6)/40]mA. If the VID inputs are left
unconnected, they will float to V
CC
at a rate controlled by parasitic
capacitance. Until the VID inputs reach their final states, slightly higher
I
VCC
current may be observed. (See the Operation section for more detail.)
Note 5:
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.)
170685f
2
U
W
U
U
W W
W
LTC1706-85
TYPICAL PERFOR A CE CHARACTERISTICS
Typical Error % vs Output Voltage
0.25
T
A
= 25°C
0.25
ERROR (%)
0
ERROR (%)
–0.25
1.0
1.2
1.6
1.4
OUTPUT VOLTAGE (V)
1.8
1706-85 G01
R
FB1
vs Temperature
10.10
70
10.05
VID PULL-UP CURRENT (µA)
R
FB1
(kΩ)
10.00
9.95
9.90
–50
Supply Current vs Temperature
1.0
ALL VID INPUTS OPEN
1.0
SUPPLY CURRENT (µA)
V
CC
= 5V
0.5
V
CC
= 3.3V
SUPPLY CURRENT (µA)
0
–50
U W
Typical Error % vs Temperature
V
OUT
= 1.05V
V
OUT
= 1.325V
V
OUT
= 1.825V
0
–0.25
–50
0
50
TEMPERATURE (°C)
100
1706-85 G02
VID Pullup Current vs Temperature
V
CC
= 3.3V
VID PIN UNDER TEST = 0V
65
60
0
50
TEMPERATURE (°C)
100
1706-85 G03
55
–50
0
50
TEMPERATURE (°C)
100
1706-85 G04
Supply Current vs Supply Voltage
ALL VID INPUTS OPEN
T
A
= 25°C
0.5
V
CC
= 2.7V
0
2.5
0
50
TEMPERATURE (°C)
100
1706-85 G05
3.0
3.5 4.0
4.5 5.0
SUPPLY VOLTAGE (V)
5.5
6.0
1706-85 G06
170685f
3
LTC1706-85
PI FU CTIO S
VID25 (Pin 1):
Programming Input. GND = LOW,
V
CC
or Float = HIGH. Refer to Table 1 for programming
information. Connect to associated VID pin of
µP.
VID0 (Pin 2):
Programming Input. GND = LOW,
V
CC
or Float = HIGH. Refer to Table 1 for programming
information. Connect to associated VID pin of
µP.
VID1 (Pin 3):
Programming Input. GND = LOW,
V
CC
or Float = HIGH. Refer to Table 1 for programming
information. Connect to associated VID pin of
µP.
VID2 (Pin 4):
Programming Input. GND = LOW,
V
CC
or Float = HIGH. Refer to Table 1 for programming
information. Connect to associated VID pin of
µP.
V
CC
(Pin 5):
Power Supply Voltage. May range from 2.7V
to 5.5V.
SENSE (Pin 6):
Regulator Output Voltage. Connect di-
rectly to regulator output sense node or V
DIFFOUT
when
used with the LTC1929 or LTC1629.
VID3 (Pin 7):
Programming Input. GND = LOW,
V
CC
or Float = HIGH. Refer to Table 1 for programming
information. Connect to associated VID pin of
µP.
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
LTC1929 or LTC1629.
BLOCK DIAGRA
V
CC
40k
VID25 1
V
CC
V
CC
5
40k
VID0 2
V
CC
SWITCH
CONTROL
LOGIC
40k
VID1 3
R
FB2
R
FB1
10k
V
CC
40k
VID2 4
VID3 7
4
W
U
U
U
6
SENSE
10 FB
9
GND
1706-85 BD
V
CC
40k
170685f
LTC1706-85
OPERATIO
The LTC1706-85 is a precision programmable resistive
divider designed specifically for use with an entire family
of Linear Technology Corporation DC/DC switching regu-
lators with 0.8V internal reference and feedback voltages.
The LTC1706-85 programs an output voltage ranging
from 1.050V to 1.825V in 25mV steps, depending on the
state of the VID input pins. The LTC1706-85 in conjunc-
tion with a Linear Technology DC/DC switching regulator
can be used to create a high performance voltage regu-
lator meeting all the requirements of the Intel VRM 8.5
specification.
Voltage Sensing and Feedback Pins
The LTC1706-85 operates by closing the loop between
the output node and the feedback node of the regulator
with an appropriate resistive divider network. The “top”
feedback resistor, R
FB1
, connected between SENSE and
FB, is a fixed value of typically 10k. The “bottom” feedback
resistor, R
FB2
, is set by the five VID inputs to generate the
desired regulator output voltage. Feedback resistors R
FB1
and R
FB2
are matched and temperature stable in order to
provide a highly accurate output voltage.
The FB pin is a sensitive node in the circuit. Care should
be taken to minimize the layout distance between the
LTC1706-85 FB node and the regulator feedback node. In
addition, it is important to keep tight ground connections
between the two chips.
VID Inputs
The desired output voltage is obtained by applying the
proper voltage or float condition to the five digital VID
inputs. Table 1 shows the translation table with each in-
put state and the corresponding regulator output voltage.
This translation is derived from and adheres to the Intel
VRM 8.5 specification.
Each VID input is pulled up by a 40k resistor in series with
a diode connected to V
CC
. To produce a digital low a VID
U
input should be grounded or driven to a low state. The
VID inputs must be driven with a maximum V
IL
of 0.8V
(V
CC
= 3.3V).
When a VID input is grounded or pulled low with a logic
gate, the power supply current will increase because of
the resistor from V
CC
through the series diode to the
input. This increase in current is calculated from:
I
Q
= N • (V
CC
– V
DIODE
)/R
PULLUP
where N is the number of grounded VID inputs. With
typical values of V
CC
= 3.3V, V
DIODE
= 0.6V and R
PULLUP
= 40k, each grounded V
IN
input will sink approximately
68µA.
To apply a digital high state the input can be either floated,
connected to V
CC
or driven by a logic gate. The VID inputs
should be driven with a minimum V
IH
of 2V (V
CC
= 3.3V).
Because of the diode between V
CC
and the pull-up resis-
tor, the maximum V
IH
is not limited to V
CC
. The VID inputs
can be driven higher than V
CC
without being clamped or
damaged. This allows the LTC1706-85 to be fully logic
compatible and operational over a wide input voltage
range, up to the 7V absolute maximum rating.
When used with the LTC1629 and LTC1929, the
LTC1706-85’s FB, SENSE, V
CC
and GND pins should be
connected respectively to the EAIN, V
DIFFOUT
, INTV
CC
and
SGND pins of the LTC1629 and LTC1929. The result of this
application is a precisely controlled, multiphase, variable
output voltage supply applicable to any low output voltage
system such as a personal computer, workstation or
network server.
In addition to the LTC1629 and LTC1929, the LTC1706-85
also programs a whole family of LTC DC/DC converters
that have an onboard 0.8V reference. The LTC1628,
LTC1735 and LTC1622 are just a few of the high efficiency
step-down switching regulators that will work equally well
with the LTC1706-85. Contact LTC Marketing for a more
complete listing of compatible DC/DC regulators.
170685f
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