General Description
The DS3908 contains two nonvolatile digital poten-
tiometers with programmable-gain amplifiers buffering
the wiper outputs. The potentiometer position and
amplifier gain are controlled through an I
2
C*-compati-
ble serial bus. The DS3908 operates in both 3.3V and
5V systems and features a write-protect pin that locks
the position of the potentiometers and gain registers. Up
to eight DS3908s can be placed on a single I
2
C bus.
Applications
Pin-Diode Biasing
Power-Supply Calibration
Cell Phones and PDAs
Portable Electronics
Features
o Two 64-Position Linear Taper Potentiometers
o Integral Wiper Buffering Amplifiers with
Selectable Gains of 1V/V, 2V/V, or 4V/V
o 100k Potentiometer End-to-End Resistance
o Low Potentiometer Temperature Coefficient
o Nonvolatile Wiper and Gain Storage
o I
2
C-Compatible Interface
o Write-Protect Pin Prevents Accidental Field
Reprogramming
o 3V to 5.5V Supply Voltage Range
o -40C to +85C Operating Temperature Range
o 14-Pin TDFN Package
DS3908
Dual, 64-Position Nonvolatile Digital
Potentiometer with Buffered Outputs
______________________________________________ Maxim Integrated Products
1
TDFN (3mm x 3mm)
TOP VIEW
2
4
5
13
11
10
H1
L1
H0
SCL
A1
A2
1
+
14
V
CC
SDA
3
12
V1
A0
6
9
V0
WP
7
8
L0
GND
DS3908
Pin Configuration
POT0
H0
V0
L0
H1
V1
L1
I
2
C
INTERFACE
SDA
SCL
A0
A1
A2
WP
VOLTAGE
REFERENCE
NV ADJUSTABLE
REFERENCE
VOLTAGE
NV ADJUSTABLE
REFERENCE
VOLTAGE
V
CC
DS3908
PGA0
POT1
PGA1
Typical Operating Circuit
Rev 0; 4/06
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
+Denotes lead-free package.
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
DS3908N+
-40C to +85C
14 TDFN
I
2
C is a trademark of Philips Corp. Purchase of I
2
C components from Maxim Integrated Products, Inc., or one of its sublicensed
Associated Companies, conveys a license under the Philips I
2
C Patent Rights to use these components in an I
2
C system, provided
that the system conforms to the I
2
C Standard Specification as defined by Philips.
DS3908
Dual, 64-Position Nonvolatile Digital
Potentiometer with Buffered Outputs
2
_____________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING CONDITIONS
(T
A
= -40C to +85C.)
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
Voltage on V
CC
, SDA, and SCL Relative to GND .....-0.5V to +6.0V
Voltage on A0, A1, A2, L0, L1, H0, H1, and WP Relative
to GND................-0.5V to (V
CC
+ 0.5V) (not to exceed +6.0V)
Operating Temperature Range ...........................-40C to +85C
Programming Temperature Range .........................0C to +70C
Storage Temperature Range .............................-55C to +125C
Soldering Temperature ............Refer to J-STD-020 Specification
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Supply Voltage
V
CC
(Note 1)
+3.0
+5.5
V
Input Logic 1
(SCL, SDA, A0, A1, A2, WP)
V
IH
0.7 x
V
CC
V
CC
+
0.3
V
Input Logic 0
(SCL, SDA, A0, A1, A2, WP)
V
IL
-0.3
0.3 x
V
CC
V
Potentiometer Voltage
(L0, L1, H0, H1)
V
CC
= +3.0V to +5.5V
-0.3
V
CC
+
0.3V
V
DC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.0V to +5.5V, T
A
= -40C to +85C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Input Leakage
I
L
-1
+1
A
Standby Supply Current
I
STBY
V
CC
= 5.5V (Note 2)
2
mA
V
OL1
3mA sink current
0
0.4
Low-Level Output Voltage
(SDA)
V
OL2
6mA sink current
0
0.6
V
I/O Capacitance
C
I/O
10
pF
WP Internal Pullup Resistance
R
WP
40
65
100
k
ANALOG POTENTIOMETER CHARACTERISTICS
(V
CC
= +3.0V to +5.5V, T
A
= -40C to +85C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
End-to-End Resistance
+25C
79
100
121
k
Absolute Linearity
INL
(Notes 3, 4)
-0.6
+0.6
LSB
Relative Linearity
DNL
(Notes 4, 5)
-0.25
+0.25
LSB
End-to-End Temperature
Coefficient
50
ppm/C
DS3908
Dual, 64-Position Nonvolatile Digital
Potentiometer with Buffered Outputs
_____________________________________________________________________
3
AC ELECTRICAL CHARACTERISTICS
(V
CC
= +3.0V to +5.5V, T
A
= -40C to +85C.) (See Figure 2.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SCL Clock Frequency
f
SCL
(Note 6)
400
kHz
Bus Free Time between STOP
and START Conditions
t
BUF
1.3
s
Hold Time (Repeated) START
Condition
t
HD:STA
0.6
s
Low Period of SCL
t
LOW
1.3
s
High Period of SCL
t
HIGH
0.6
s
Data Hold Time
t
HD:DAT
0
0.9
s
Data Setup Time
t
SU:DAT
100
ns
Start Setup Time
t
SU:STA
0.6
s
SDA and SCL Rise Time
t
R
(Note 7)
20 + 0.1C
B
300
ns
SDA and SCL Fall Time
t
F
(Note 7)
20 + 0.1C
B
300
ns
STOP Setup Time
t
SU:STO
0.6
s
SDA and SCL Capacitance
C
B
(Note 7)
400
pF
EEPROM Write Time
t
W
(Note 8)
10
17
ms
Startup Time
t
ST
V
CC
= 3.0V
40
s
PROGRAMMABLE-GAIN AMPLIFIER CHARACTERISTICS
(V
CC
= +3.0V to +5.5V, T
A
= -40C to +85C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Common-Mode Input Voltage
CMV
IN
0
V
CC
- 1.5
V
R
L
2k, G = 1V/V
0.975
1
1.025
R
L
2k, G = 2V/V
1.925
2
2.05
Gain
G
R
L
2k, G = 4V/V
3.850
4
4.10
V/V
Output Voltage Range
V
OUT
R
L
= 2k
, -1mA < I
OUT
< 1mA
0.3
V
CC
- 0.3
V
Power-Supply Rejection Ratio
PSRR
60
90
dB
Output Source Current
I
OUT:SOURCE
V
OUT
= 0V, Hx = Lx = 1V
-15
mA
Output Sink Current
I
OUT:SINK
V
OUT
= 1V, Hx = Lx = 0V
15
mA
Unity-Gain Frequency
f
T
Gain = 1V/V, position 3Fh
3.5
MHz
Amplifier Capacitive Loading
C
L
100
pF
Input Offset Voltage
V
OS
-9
+9
mV
Load Regulation
-1mA < I
OUT
< 1mA
800
2200
V/mA
Output-Voltage Slew Rate
R
L
= 10k
, C
L
= 10pF
270
840
V/ms
DS3908
Dual, 64-Position Nonvolatile Digital
Potentiometer with Buffered Outputs
4
_____________________________________________________________________
NONVOLATILE MEMORY CHARACTERISTICS
(V
CC
= +3.0V to +5.5V.)
PARAMETER
SYMBOL
CONDITIONS
MIN
MAX
UNITS
EEPROM Write Cycles
At +70C
50,000
Note 1:
All voltages are referenced to ground.
Note 2:
I
STBY
specified assuming control pins are connected as follows: WP must be disconnected or connected high. H terminal
connected to V
CC
, L terminal connected to GND, potentiometer position 1Dh, PGA is at 2V/V, A0 to A2 connected to V
CC
,
SDA and SCL connected to V
CC
, with no load.
Note 3:
Absolute linearity is used to measure expected wiper voltage as determined by wiper position in a voltage-divider
configuration.
Note 4:
This specification only refers to the potentiometers, and does not include the gain and offset error due to the PGA.
Note 5:
Relative linearity is used to determine the change of wiper voltage between two adjacent wiper positions in a voltage-
divider configuration.
Note 6:
I
2
C interface timing shown is for fast-mode (400kHz) operation. This device is also backward-compatible with I
2
C stan-
dard-mode timing.
Note 7:
C
B
--total capacitance of one bus line in picofarads, timing referenced to 0.9 x V
CC
and 0.1 x V
CC
.
Note 8:
EEPROM write begins after a stop condition occurs.
0
0.6
0.4
0.2
0.8
1.0
1.2
1.4
1.6
1.8
2.0
3.0
4.0
3.5
4.5
5.0
5.5
STANDBY SUPPLY CURRENT
vs. SUPPLY VOLTAGE
DS3908 toc01
V
CC
I
STBY
(mA)
Hx = V
CC
, Lx = GND
A0 TO A2 = V
CC
SDA, SCL = V
CC
POT AT 1Dh
GAIN = 2V/V
NO LOAD
+85
C +25C
-40
C
0
0.6
0.4
0.2
0.8
1.0
1.2
1.4
1.6
1.8
2.0
-40
10
-15
35
60
85
STANDBY SUPPLY CURRENT
vs. TEMPERATURE
DS3908 toc02
TEMPERATURE (
C)
I
STBY
(mA)
3.3V
5.5V
4.0V
1
10,000
1,000,000
STANDBY SUPPLY CURRENT
vs. SCL FREQUENCY
DS3908 toc03
SCL FREQUENCY (Hz)
I
STBY
(mA)
100
1.16400
1.15000
1.15200
1.15400
1.15600
1.15800
1.16200
1.16000
Typical Operating Characteristics
(T
A
= +25C, unless otherwise noted.)
1.30000
1.10000
1.50000
1.40000
1.60000
1.70000
1.80000
1.90000
1.00000
0
10
20
30
40
50
60
OUTPUT VOLTAGE vs. POT SETTING
DS3908 toc04
POT SETTING (DEC)
OUTPUT VOLTAGE AT Vx (mA)
GAIN = 1V/V
Hx = 1V
Lx = 0.3V
0.001
0.01
0.1
1
10
100
V
OL
vs. I
OUT:SINK
1
0.1
0.01
0.001
10
DS3908 toc05
I
OUT:SINK
(mA)
V
OL
(V)
+85
C +25C
-40
C
0.001
0.01
0.1
1
10
100
V
CC
- V
OH
vs. I
OUT:SOURCE
1
0.1
0.01
0.001
10
DS3908 toc06
I
OUT:SOURCE
(mA)
V
CC
- V
OH
(V)
+85
C +25C
-40
C
DS3908
Dual, 64-Position Nonvolatile Digital
Potentiometer with Buffered Outputs
_____________________________________________________________________
5
-1.0
-0.4
-0.6
-0.8
-0.2
0
0.2
0.4
0.6
0.8
1.0
-40
10
-15
35
60
85
NORMALIZED POT END-END RESISTANCE
vs. TEMPERATURE
DS3908 toc07
TEMPERATURE (
C)
NORMALIZED POT END-END RESISTANCE (
/
)
V
CC
= 5V
-1.25
-0.10
-0.15
-0.20
-0.05
0
0.05
0.10
0.15
0.20
0.25
0
10
20
30
40
50
60
POT INL vs. SETTING
DS3908 toc08
POT0 SETTING (DEC)
POT INL (LSB)
GAIN = 1V/V
-1.25
-0.10
-0.15
-0.20
-0.05
0
0.05
0.10
0.15
0.20
0.25
0
10
20
30
40
50
60
POT DNL vs. SETTING
DS3908 toc09
POT0 SETTING (DEC)
POT DNL (LSB)
GAIN = 1V/V
-0.5
0.6
-0.2
-0.4
-0.3
0.1
0
-0.1
0.5
0.4
0.3
0.2
0.3
1.5
1.9
0.7
1.1
2.3
2.7
3.1
3.5
TYPICAL PGA OFFSET
vs. COMMON-MODE INPUT VOLTAGE
DS3908 toc10
COMMON-MODE INPUT VOLTAGE (V)
TYPICAL PGA OFFSET (mV)
GAIN = 1V/V
DATA OFFSET TO SHOW 0 AT 2V CMV
IN
+85
C
+25
C
-40
C
-0.2
-0.1
-0.15
0.05
0
-0.05
0.2
0.15
0.1
0.25
-40
10
-15
35
60
85
TYPICAL PGA OFFSET
vs. TEMPERATURE
DS3908 toc11
TEMPERATURE (
C)
TYPICAL PGA OFFSET (mV)
CMV
IN
= 0.3V
CMV
IN
= 2.0V
CMV
IN
= 3.5V
Pin Description
TDFN PIN
NAME
FUNCTION
1
SDA
I
2
C Serial Data. Input/output for I
2
C data.
2
SCL
I
2
C Serial Clock. Input for I
2
C clock.
3, 4, 5
A0, A1, A2
Address-Select Inputs. Determines I
2
C address. Device address is 1010A
2
A
1
A
0
. (See the I
2
C Slave
Address and Address Pins section for more details.)
6
WP
Write-Protect Input. Must be grounded to write to the registers. An internal pullup will lock the register
values if this pin is not connected.
7
GND
Ground Terminal
8, 11
L0, L1
Potentiometer Low Terminals. Voltages on these pins should remain between GND and V
CC
.
9, 12
V0, V1
Amplifier Outputs
10, 13
H0, H1
Potentiometer High Terminals. Voltages on these pins should remain between GND and V
CC
.
14
V
CC
Supply Voltage Terminal
Typical Operating Characteristics (continued)
(T
A
= +25C, unless otherwise noted.)
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