LTC1706-61
5-Bit VID Voltage
Programmer for AMD
Opteron CPUs
FEATURES
s
s
DESCRIPTIO
s
s
s
Programs Regulator Output Voltage Range from
0.8V to 1.55V in 25mV Steps
Programs a Wide Range of Linear Technology
DC/DC Converters with a 0.6V Reference
±0.35%
Accurate Output Voltage
Built-In 40k Pull-Up Resistors on VID Inputs
Available in MSOP-10 Package
The LTC
®
1706-61 is a precision, digitally programmed,
resistive ladder which adjusts the output of any 0.6V
referenced regulator. Depending on the state of the five
VID inputs, an output voltage between 0.8V and 1.55V is
programmed in 25mV increments.
The LTC1706-61 is designed specifically to program
an entire family of Linear Technology DC/DC converters
with on board 0.6V references.
The LTC1706-61 programs the following Linear
Technology DC/DC converter products: LTC1629-6,
LTC3714, LTC3731 and LTC3778. (Consult factory for
additional DC/DC converter products.)
, LTC and LT are registered trademarks of Linear Technology Corporation.
AMD Opteron is a trademark of Advanced Micro Devices, Inc.
APPLICATIO S
s
s
s
AMD Opteron
TM
Processor Power Supply
Workstations and Servers
Large Memory Array Supply
TYPICAL APPLICATIO
5-Bit VID-Controlled High Current Application (Simplified Block Diagram)
V
IN
4.5V TO 22V
V
IN
LTC1629-6
VID0
VID1
FROM
µP
V
CC
SENSE
TG1
SW1
INTV
CC
V
DIFFOUT
SGND
FB
GND
EAIN
I
TH
TG2
SW2
BG2
V
IN
4.5V TO 22V
V
IN
LTC1629-6
TG1
SW1
BG1
PGND
SGND
EAIN
I
TH
TG2
SW2
BG2
1706-61 TA01
L1
BG1
PGND
V
IN
VID2 LTC1706-61
VID3
VID4
L2
L3
V
IN
L4
U
R
SENSE1
U
U
+
V
OUT
0.8V TO 1.55V
UP TO 80A
C
OUT
R
SENSE2
R
SENSE3
R
SENSE4
170661f
1
LTC1706-61
ABSOLUTE
MAXIMUM
RATINGS
(Note 1)
PACKAGE/ORDER INFORMATION
TOP VIEW
VID0
VID1
VID2
VID3
V
CC
1
2
3
4
5
10
9
8
7
6
FB
GND
NC
VID4
SENSE
(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 Ambient 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
ORDER PART
NUMBER
LTC1706EMS-61
MS
PART MARKING
LTK9
MS PACKAGE
10-LEAD PLASTIC MSOP
T
JMAX
= 110°C,
θ
JA
= 120°C/ W
Consult LTC Marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
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.
SYMBOL
V
CC
I
VCC
R
FB-SENSE
V
OUT
Error %
R
PULLUP
VID
TH
I
VID-LEAK
V
PULLUP
PARAMETER
Operating Supply Voltage Range
Supply Current
Resistance Between SENSE and FB
Output Voltage Accuracy
VID Input Pull-Up Resistance
VID Input Voltage Threshold
VID Input Leakage Current
VID Pull-Up Voltage
CONDITIONS
(Note 3)
q
q
MIN
2.7
6
– 0.35
TYP
0.1
10
40
MAX
5.5
5
14
+ 0.35
0.4
V
DIODE
= 0.6V (Note 4)
V
IL
(2.7V
≤
V
CC
≤
5.5V)
V
IH
(2.7V
≤
V
CC
≤
5.5V)
V
CC
< VID < 7V (Note 4)
V
CC
= 3.3V
V
CC
= 5V
1.6
0.01
2.8
4.5
±1
UNITS
V
µA
kΩ
%
kΩ
V
V
µA
V
V
Note 1:
Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2:
The LTC1706EMS-61 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 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.)
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LTC1706-61
TYPICAL PERFORMANCE CHARACTERISTICS
I
VID-PULLUP
vs Temperature
140
120
100
80
60
40
20
–50
0
–50
0
2.5
V
CC
= 5V
VID4 = 0V
VID0 = VID1 = VID2 = VID3 = OPEN
2.0
ALL VID INPUTS OPEN
1.5
VID PULL-UP CURRENT (µA)
SUPPLY CURRENT (µA)
SUPPLY CURRENT (µA)
0
50
TEMPERATURE (°C)
VID
VID Sense Accuracy
0.35
0.25
0.35
0.25
VID
ACCURACY
( %)
VID
ACCURACY
( %)
0.15
0.05
–0.05
–0.15
–0.25
–0.35
0.775
V
CC
= 5.5V
V
CC
= 2.7V
0.05
–0.05
–0.15
–0.25
–0.35
–60 –40 –20
V
SENSE
= 0.8V
V
SENSE
= 1.55V
R
FB1
(kΩ)
0.975
1.175
1.375
SENSE VOLTAGE (V)
1706-61 G04
PIN FUNCTIONS
VID0 (Pin 1):
LSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID0 adds 25mV
to the output sense voltage.
VID1 (Pin 2):
4th MSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID1 adds 50mV
to the output sense voltage.
VID2 (Pin 3):
3rd MSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID2 adds 100mV
to the output sense voltage.
VID3 (Pin 4):
2nd MSB Programming Input. Low = GND,
High = V
CC
or Float. Grounding VID3 adds 200mV
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.
VID4 (Pin 7):
MSB Programming Input. Low = GND, High
= V
CC
or Float. Grounding VID4 adds 400mV to the output
sense voltage.
NC (Pin 8):
No Connect.
GND (Pin 9):
Ground. Connect to regulator signal ground.
FB (Pin 10):
Feedback Input. Connect to the 0.6V feedback
pin of a compatible regulator.
170661f
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Supply Current vs Temperature
1.0
Supply Current vs Supply Voltage
ALL VID INPUTS OPEN
T
A
= 25°C
1.0
V
CC
= 5V
0.5
V
CC
= 3.3V
0.5
V
CC
= 2.7V
100
1706-61 G01
0
50
TEMPERATURE (°C)
100
1706-61 G02
3.0
3.5 4.0
4.5 5.0
SUPPLY VOLTAGE (V)
5.5
6.0
1706-61 G03
VID Sense Accuracy vs
Temperature
V
CC
= 5.5V
10.10
R
FB1
vs Temperature
0.15
V
SENSE
= 1.15V
10.05
10.00
9.95
1.575
0
20
40
60
80
100
9.90
–50
TEMPERATURE (°C)
1706-61 G05
0
50
TEMPERATURE (°C)
100
1706-61 G06
U
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LTC1706-61
PIN FUNCTIONS
PIN
1
2
3
4
5
6
7
8
9
10
NAME
VID0
VID1
VID2
VID3
V
CC
SENSE
VID4
NC
GND
FB
Ground
0.6V Feedback Input
0
0
0.6
1.5
– 0.3
– 0.3
7
7
DESCRIPTION
LSB Programmable Input
4th MSB Programmable Input
3rd MSB Programmable Input
2nd MSB Programmable Input
Power Supply
Regulator Output Voltage
1st MSB Programmable Input
NOMINAL (V)
MIN
TYP
MAX
0
0
0
0
2.7
0.8
0
V
CC
V
CC
V
CC
V
CC
5.5
1.55
V
CC
ABSOLUTE MAX (V)
MIN
MAX
– 0.3
– 0.3
– 0.3
– 0.3
– 0.3
– 0.3
– 0.3
7
7
7
7
7
7
7
BLOCK DIAGRA
VID0 1
V
CC
V
CC
5
VID1 2
V
CC
SWITCH
CONTROL
LOGIC
40k
VID2 3
VID3 4
OPERATIO
The LTC1706-61 is a precision resistive divider designed
specifically for use with an entire family of Linear
Technology Corporation DC/DC switching regulators with
0.6V internal reference and feedback voltage. The
LTC1706-61 produces an output voltage ranging from
0.8V to 1.55V 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.
4
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U
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U
V
CC
40k
40k
R
FB1
6
SENSE
10 FB
R
FB2
9
GND
1706-61 BD
V
CC
V
CC
40k
VID4 7
40k
The “top” feedback resistor, R
FB1
, connected between
SENSE and FB, is typically 10k 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
.
170661f
LTC1706-61
OPERATIO
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.
Table 1. VID Inputs and Corresponding Output Voltage
CODE
00000
00001
00010
00011
00100
00101
00110
00111
01000
01001
01010
01011
01100
01101
01110
01111
10000
10001
10010
10011
10100
10101
10110
10111
11000
11001
11010
11011
11100
11101
11110
11111
VID4
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
Float
VID3
GND
GND
GND
GND
GND
GND
GND
GND
Float
Float
Float
Float
Float
Float
Float
Float
GND
GND
GND
GND
GND
GND
GND
GND
Float
Float
Float
Float
Float
Float
Float
Float
VID2
GND
GND
GND
GND
Float
Float
Float
Float
GND
GND
GND
GND
Float
Float
Float
Float
GND
GND
GND
GND
Float
Float
Float
Float
GND
GND
GND
GND
Float
Float
Float
Float
VID1
GND
GND
Float
Float
GND
GND
Float
Float
GND
GND
Float
Float
GND
GND
Float
Float
GND
GND
Float
Float
GND
GND
Float
Float
GND
GND
Float
Float
GND
GND
Float
Float
VID0
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
GND
Float
OUTPUT
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
1.050V
1.025V
1.000V
0.975V
0.950V
0.925V
0.900V
0.875V
0.850V
0.825V
0.800V
*0.775V
*Represents codes without a defined output (shutdown) voltage as
specified in AMD specifications. The LTC1706-61 interprets these codes
as a valid input and produces an output voltage as follows:
(11111) = 0.775V.
U
When all five VID inputs are high or floating, such as when
no CPU is present in a system, a regulated 0.775V output
is generated at V
SENSE
.
Each VID input pin is pulled up by a 40k resistor in series
with a diode connected to V
CC
. Therefore, it should be
grounded (or driven low) to produce a digital low input. It
can either be floated or connected to V
CC
to get a digital
high input. The series diode is included to prevent the
input from being damaged or clamped when it is driven
higher than V
CC
.
Voltage Sensing and Feedback Pins
The FB pin is a high impedance node that requires mini-
mum layout distance to reduce extra loading and
unwanted stray pickup.
When used with the LTC1629-6, the LTC1706-61’s FB,
SENSE, V
CC
and GND pins should be connected, respec-
tively, with the EAIN, V
DIFFOUT
, INTV
CC
and SGND pins of
the LTC1629-6. The result of this application is a precisely
controlled, variable output voltage supply to any low
voltage, high current system such as a powerful personal
computer, workstation or network server.
VID Input Characteristics
The VID inputs should be driven with a maximum V
IL
of
0.4V and a minimum V
IH
of 1.6V. However, the VID input
range is not limited to values less than V
CC
. Because of the
internal diode between V
CC
and the pull-up resistor, the
inputs can go higher than V
CC
without being clamped to
V
CC
or damaging the input.
This allows the LTC1706-61 to be fully logic compatible
and operational over a higher input voltage range (less
than the 7V absolute maximum rating).
When a VID input is grounded, there will be a higher
quiescent current flow from V
CC
because of a resistor from
V
CC
through a series diode to each one of the inputs. This
increase in quiescent current is calculated from:
I
Q
= N(V
CC
– V
DIODE
)/R
PULLUP
N is the number of grounded VID inputs. V
DIODE
is typically
0.6V while R
PULLUP
has a typical pull-up resistance of
40kΩ.
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