General Description
The MAX5400/MAX5401 digital potentiometers offer
256-tap SOT-PoT™ digitally controlled variable resis-
tors in tiny 8-pin SOT23 packages. Each device func-
tions as a mechanical potentiometer, consisting of a
fixed resistor string with a digitally controlled wiper con-
tact. They operate from +2.7V to +5.5V single-supply
voltages and use an ultra-low supply current of 0.1µA.
These devices also provide glitchless switching
between resistor taps, as well as a convenient power-
on reset that sets the wiper to the midscale position at
power-up. A low 5ppm/°C ratiometric temperature coef-
ficient makes it ideal for applications requiring low drift.
The MAX5400/MAX5401 serve well in applications
requiring digitally controlled resistors, including
adjustable voltage references and programmable gain
amplifiers (PGAs). A nominal end-to-end resistor tem-
perature coefficient of 50ppm/°C allows these parts to
be used as variable resistors in applications such as
low-tempco adjustable gain and other circuit configura-
tions.
Two resistance values are available: 50kΩ(MAX5400)
and 100kΩ(MAX5401). Each device is guaranteed over
the extended industrial temperature range (-40°C to
+85°C).
________________________Applications
Mechanical Potentiometer Replacement
Low-Drift PGAs
Adjustable Voltage References
Features
♦Miniature 8-Pin SOT23 (3mm x 3mm)
♦256 Tap Positions
♦Ultra-Low 0.1µA Supply Current
♦Single-Supply Operation: +2.7V to +5.5V
♦Low Ratiometric Temperature Coefficient:
5ppm/°C
♦Power-On Reset: Wiper Goes to Midscale
(Position 128)
♦Glitchless Switching Between the Resistor Taps
♦3-Wire SPI™-Interface Compatible
♦50kΩ/100kΩResistor Values
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
________________________________________________________________ Maxim Integrated Products 1
19-1848; Rev 0; 10/00
Ordering Information
SOT-PoT is a trademark of Maxim Integrated Products.
SPI is a trademark of Motorola, Inc.
Pin Configuration appears at end of data sheet.
PART TEMP.
RANGE
PIN-
PACKAGE R (kΩ)
MAX5400EKA-T -40°C to +85°C 8-SOT23 50
MAX5401EKA-T -40°C to +85°C 8-SOT23 100
For price, delivery, and to place orders, please contact Maxim Distribution at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
MAX5400/MAX5401
POR
8
8-BIT
SHIFT
REGISTER
CLOCK
LOGIC
8-BIT
LATCH
SCLK
DIN
CS
8
H
W
L
DECODER
VDD
GND
Functional Diagram
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VDD = +5V, VH= VDD, VL= 0, TA= TMIN to TMAX. Typical values are at TA= +25°C, unless otherwise noted. Parameters are mea-
sured at TA= +25°C. Values over full temperature range are guaranteed by design.)
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.
VDD to GND............................................................. -0.3V to +6V
DIN, SCLK, CS to GND ............................................-0.3V to +6V
H, L, W to GND...........................................-0.3V to (VDD + 0.3V)
Maximum Continuous Current into
Pins H, L, and W ...........................................................±1mA
Continuous Power Dissipation (TA= +70°C)
8-Pin SOT23 (derate 8.7mW/°C above +70°C)...........697mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ..................................................…+150°C
Storage Temperature Range .............................-65°C to +150°C
Lead Temperature (soldering, 10s) .................................+300°C
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DC PERFORMANCE (Voltage Divider Mode)
Resolution N 8 Bits
Integral Nonlinearity
(Notes 1, 2) INL ±1/2 LSB
Differential Nonlinearity
(Notes 1, 2) DNL ±1/2 LSB
End-to-End Resistor Tempco TCR50 ppm/°C
Ratiometric Resistor Tempco 5 ppm/°C
MAX5400 -0.8
Full-Scale Ratio Error MAX5401 -0.4 LSB
MAX5400 +0.8
Zero-Scale Ratio Error MAX5401 +0.4 LSB
POWER SUPPLIES
Supply Voltage VDD 2.7 5.5 V
VDD = 5V 0.7 5 µA
Supply Current IDD CS = SCLK = DIN = VDD VDD = 2.7V 0.1 µA
DC PERFORMANCE (Variable Resistor Mode)
Resolution N 8 Bits
VCC = 5V ±1
MAX5400 ±1.5
Integral Nonlinearity
(Notes 1, 3) INL VCC = 3V MAX5401 ±1
LSB
VCC = 5V ±1/2
Differential Nonlinearity
(Notes 1, 3) DNL VCC = 3V ±1/2 LSB
DC PERFORMANCE (Resistor Characteristics)
Wiper Resistance (Note 4) RW250 800 Ω
Wiper Capacitance CW25 pF
MAX5401 75 100 125
End-to-End Resistance RHL MAX5400 37.5 50 62.5 kΩ
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
_______________________________________________________________________________________ 3
Note 1: Linearity is defined in terms of the H to L code-dependent resistance.
Note 2: The DNL and INL are measured with the potentiometer configured as a voltage-divider with H = VDD and L = 0. The wiper
terminal is unloaded and measured with an ideal voltmeter.
Note 3: The DNL and INL are measured with the potentiometer configured as a variable resistor. H is unconnected and L = 0. The
wiper terminal is driven with a source current of 80µA for the 50kΩconfiguration and 40µA for the 100kΩconfiguration.
Note 4: The wiper resistance is measured assuming the source currents given in Note 2.
Note 5: Digital timing is guaranteed by design.
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
DIGITAL INPUTS
Input High Voltage VIH VCC = 5V 0.7 ✕ VDD V
Input Low Voltage VIL VCC = 5V 0.3 ✕ VDD V
Input High Voltage VIH VCC = 3V 0.7 ✕ VDD V
Input Low Voltage VIL VCC = 3V 0.3 ✕ VDD V
Input Leakage Current ±1.0 µA
Input Capacitance 5.0 pF
TIMING CHARACTERISTICS (Voltage Divider Mode)
MAX5400 (to 50% of final value, from code 0
to code 128) 300
Wiper Settling Time tIL MAX5401 (to 50% of final value, from code 0
to code 128) 600
ns
TIMING CHARACTERISTICS (Digital) (Note 5)
SCLK Clock Period tCP 100 ns
SCLK Pulse Width High tCH 40 ns
SCLK Pulse Width Low tCL 40 ns
CS Fall to SCLK Rise Setup
Time tCSS 40 ns
SCLK Rise to CS Rise Hold Time tCSH 0ns
DIN Setup Time tDS 40 ns
DIN Hold Time tDH 0ns
SCLK Rise to CS Fall Delay tCS0 10 ns
CS Rise to SCLK Rise Hold tCS1 40 ns
CS Pulse Width High tCSW 100 ns
ELECTRICAL CHARACTERISTICS (continued)
(VDD = +5V, VH= VDD, VL= 0, TA= TMIN to TMAX. Typical values are at TA= +25°C, unless otherwise noted. Parameters are mea-
sured at TA= +25°C. Values over full temperature range are guaranteed by design.)
0
0.4
0.2
0.8
0.6
1.0
SUPPLY CURRENT
vs. TEMPERATURE
MAX5400toc09
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
-40 -20 020406080
-30 -10 10 30 70
50
VDD = +3V
VDD = +5V
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
4 _______________________________________________________________________________________
Typical Operating Characteristics
(TA= +25°C, unless otherwise noted.)
0
200
100
400
300
600
500
021345
WIPER RESISTANCE vs. VOLTAGE
MAX5400 toc01
WIPER VOLTAGE (V)
WIPER RESISTANCE (Ω)
VDD = +3V
VDD = +5V
-0.11
-0.05
-0.07
-0.09
-0.03
-0.01
0.03
0.01
0.05
-40 -30 -20 -10 0 10 20 30 40 50 60 70 80
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE
MAX5400toc02
TEMPERATURE (°C)
END-TO-END RESISTANCE % CHANGE
100kΩ
50kΩ
0
20
10
40
30
60
50
70
90
80
100
0649632 128 160 192 224 256
W-to-L RESISTANCE vs. INPUT CODE
(100kΩ)
MAX5400 Toc03
INPUT CODE-DECIMAL
W-TO-L RESISTANCE (kΩ)
VDD = 2.7V
to 5.5V
0
10
5
20
15
30
25
35
45
40
50
0649632 128 160 192 224 256
W-to-L RESISTANCE vs. INPUT CODE
(50kΩ)
MAX5400 Toc04
INPUT CODE-DECIMAL
W-TO-L RESISTANCE (kΩ)
VDD = 2.7V
to 5.5V
-0.020
-0.010
-0.015
-0.005
0
0.005
0.015
0.010
0.020
0649632 128 160 192 224 256
VARIABLE RESISTOR DNL
vs. INPUT CODE (50kΩ)
MAX5400 Toc05
INPUT CODE-DECIMAL
(LSB)
-0.20
-0.15
-0.05
-0.10
0.05
0
0.10
0.15
0.20
0649632 128 160 192 224 256
VARIABLE RESISTOR INL vs. INPUT CODE
(50kΩ)
MAX5400 Toc06
INPUT CODE-DECIMAL
(LSB)
-1.020
-0.010
-0.015
-0.005
0.005
0
0.010
0.015
0.020
0649632 128 160 192 224 256
VARIABLE RESISTOR DNL
vs. INPUT CODE (100kΩ)
MAX5400 Toc07
INPUT CODE-DECIMAL
(LSB)
-0.20
-0.10
-0.15
-0.05
0.05
0
0.15
0.10
0.20
0649632 128 160 192 224 256
VARIABLE RESISTOR INL
vs. INPUT CODE (100kΩ)
MAX5400 Toc08
INPUT CODE-DECIMAL
(LSB)
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
_______________________________________________________________________________________ 5
MAX5400 Toc10
TAP-to-TAP SWITCHING TRANSIENT
(FROM CODE 127 toc CODE 128)
10mV/div
2.5V
5V/div
0
CS
VW-L
10
0.0001
034215
SUPPLY CURRENT vs.
INPUT LOGIC VOLTAGE
0.001
MAX5400 Toc11
DIGITAL INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
0.01
0.1
1
VDD = +5V
VDD = +3V
Typical Operating Characteristics (continued)
(TA= +25°C, unless otherwise noted.)
-0.10
-0.06
-0.08
-0.02
-0.04
0.02
0
0.04
0.08
0.06
0.10
0649632 128 160 192 224 256
VOLTAGE DIVIDER DNL
vs. INPUT CODE (50kΩ)
MAX5400 Toc12
INPUT CODE-DECIMAL
(LSB)
-0.20
-0.10
-0.15
-0.05
0.05
0
0.10
0.15
0.20
0649632 128 160 192 224 256
VOLTAGE DIVIDER INL
vs. INPUT CODE (50kΩ)
MAX5400 Toc13
INPUT CODE-DECIMAL
(LSB)
VDD = +2.7V to +5.5V
PIN NAME FUNCTION
1 L Low Terminal of Resistor
2 GND Ground
3CS Chip Select Input
4 DIN Serial Data Input
5 SCLK Clock Input
6V
DD Power Supply. Bypass with a 0.1µF capacitor to GND.
7 W Wiper Terminal
8 H High Terminal of Resistor
Pin Description
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
6 _______________________________________________________________________________________
Detailed Description
The MAX5400/MAX5401 consists of 255 fixed resistors
in series between pins H and L. The potentiometer
wiper (pin W) can be programmed to access any one
of the 256 different tap points on the resistor string. The
MAX5400/MAX5401 uses a 3-wire serial data interface
to control the wiper tap position. This write-only inter-
face contains three inputs: Chip-Select (CS), Data In
(DIN), and Data Clock (SCLK). When CS is taken low,
data from the DIN pin is synchronously loaded into the
8-bit serial shift register on the rising edge of each
SCLK pulse. The MSB is shifted in first as shown in
Figure 4. Note that if CS is not kept low during the entire
data stream, the data will be corrupted and the device
will need to be reloaded. After all 8 data bits have been
loaded into the shift register, they are latched into the
decoder once CS is taken high. The decoder switches
the potentiometer wiper to the tap position that corre-
sponds to the 8-bit input data. Each resistor cell is
50kΩ/255 or 196.1Ωfor the MAX5400 and 100kΩ/255
or 392.2Ωfor the MAX5401.
The MAX5400/MAX5401 feature power-on reset (POR)
circuitry that sets the wiper to the midscale position at
power-up by loading a binary value of 128 into the 8-bit
latch.
The MAX5400/MAX5401 can be used as a variable
resistor by connecting pin W to either pin H or pin L.
POT REGISTER LOADED
1ST CLOCK PULSE
SCLK
DIN
MSB LSB
D0D1D2D3D4D5D6D7
8TH CLOCK PULSE
TIME
CS
Figure 2. Serial Interface Timing Diagram
SCLK
DIN
tCSO tCSS
tCL
tCH
tDS
tDH
tCP tCSH
tCS1
tCSW
CS
Figure 3. Detailed Serial Interface Timing Diagram
Applications Information
The MAX5400/MAX5401 are intended for a variety of
circuits that require accurate, fine-tuning adjustable
resistance, such as adjustable voltage or adjustable
gain circuit configurations. The MAX5400/MAX5401 are
primarily used in either a potentiometer divider or a
variable resistor configuration.
Adjustable Current-to-Voltage Converter
Figure 5 shows the MAX5400/MAX5401 being used
with a MAX4250 low-noise op amp to fine tune a cur-
rent-to-voltage converter. Pins H and W of the
MAX5400/MAX5401 are connected to the node
between R3 and R2 and pin L is connected to ground.
Adjustable Gain Amplifier
The MAX5400/MAX5401 are used again with the
MAX4250 to make a digitally adjustable gain circuit as
shown in Figure 6. The normal feedback resistor is
replaced with the MAX5400/MAX5401 in a variable
resistor configuration so that the gain of the circuit can
be digitally controlled.
Adjustable Voltage Reference
In Figure 7, the MAX5400/MAX5401 are shown with the
MAX6160 to make an adjustable voltage reference. In
this circuit, the H pin of the MAX5400/MAX5401 is con-
nected to the OUT pin of the MAX6160, the L pin of the
MAX5400/MAX5401 is connected to GND, and the W
pin of the MAX5400/MAX5401 is connected to the ADJ
pin of the MAX6160. The MAX5400/MAX5401 allow pre-
cise tuning of the voltage reference output. A low
5ppm/°C ratiometric tempco allows a very stable
adjustable voltage over temperature.
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
_______________________________________________________________________________________ 7
+5V
R3
VO / IS = R3(1 + R2 / R1)+ R2
R2
R1
MAX4250
VO
Figure 5. I to V Converter
+5V
VS
VO
R2
VO/ VS = 1 + R2 / R1
R1
MAX4250
Figure 6. Noninverting Amplifier
DATA WORD
B0 (D7) B1 (D6) B2 (D5) B3 (D4) B4 (D3) B5 (D2) B6 (D1) B7 (D0)
(MSB)
FIRST
BIT IN
(LSB)
LAST
BIT IN
Figure 4. Serial Data Format
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8_____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2000 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
Chip Information
TRANSISTOR COUNT: 3769
TECHNOLOGY: BiCMOS
VOREF
VIN
GND
ADJ
OUT H
W
L
VO = 1.23V × FOR MAX5401
VO = 1.23V × FOR MAX5400
MAX6160
+5V
100kΩ
R2(kΩ)
50kΩ
R2(kΩ)
VDD
SCLKDIN
1
2
8
7
H
WGND
CS
L
SOT23
TOP VIEW
3
4
6
5
MAX5400/
MAX5401
Figure 7. Adjustable Voltage Reference
Pin Configuration