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MAX5400EKA+T-MAX5401EKA+-MAX5401EKA+T
256-Tap SOT-PoT, Low-Drift Digital Potentiometers in SOT23
General DescriptionThe 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).
________________________ApplicationsMechanical Potentiometer Replacement
Low-Drift PGAs
Adjustable Voltage References
FeaturesMiniature 8-Pin SOT23 (3mm x 3mm)256 Tap PositionsUltra-Low 0.1µA Supply CurrentSingle-Supply Operation: +2.7V to +5.5VLow Ratiometric Temperature Coefficient:
5ppm/°CPower-On Reset: Wiper Goes to Midscale
(Position 128)Glitchless Switching Between the Resistor Taps3-Wire SPI™-Interface Compatible50kΩ/100kΩResistor Values
MAX5400/MAX5401
256-Tap SOT-PoT
Low-Drift Digital Potentiometers in SOT2319-1848; Rev 0; 10/00
Ordering InformationSOT-PoT is a trademark of Maxim Integrated Products.
SPI is a trademark of Motorola, Inc.
Pin Configuration appears at end of data sheet.
PARTTEMP.
RANGE
PIN-
PACKAGER (kΩ)
MAX5400EKA-T-40°C to +85°C8-SOT2350
MAX5401EKA-T-40°C to +85°C8-SOT23100
MAX5400/MAX5401
POR
8-BIT
SHIFT
REGISTER
CLOCK
LOGIC
8-BIT
LATCH
SCLK
DIN
DECODER
VDD
GND
Functional Diagram
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS(VDD= +5V, VH= VDD, VL= 0, TA= TMINto 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.
VDDto 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
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
DC PERFORMANCE (Voltage Divider Mode)ResolutionN8Bits
Integral Nonlinearity
(Notes 1, 2)INL±1/2LSB
Differential Nonlinearity
(Notes 1, 2)DNL±1/2LSB
End-to-End Resistor TempcoTCR50ppm/°C
Ratiometric Resistor Tempco5ppm/°C
MAX5400-0.8Full-Scale Ratio ErrorMAX5401-0.4LSB
MAX5400+0.8Zero-Scale Ratio ErrorMAX5401+0.4LSB
POWER SUPPLIESSupply VoltageVDD2.75.5V
VDD = 5V0.75µASupply CurrentIDDCS = SCLK = DIN = VDDVDD = 2.7V0.1µA
DC PERFORMANCE (Variable Resistor Mode)ResolutionN8Bits
VCC = 5V±1
MAX5400±1.5Integral Nonlinearity
(Notes 1, 3)INLVCC = 3VMAX5401±1
LSB
VCC = 5V±1/2Differential Nonlinearity
(Notes 1, 3)DNLVCC = 3V±1/2LSB
DC PERFORMANCE (Resistor Characteristics)Wiper Resistance (Note 4)RW250800Ω
Wiper CapacitanceCW25pF
MAX540175100125End-to-End ResistanceRHLMAX540037.55062.5kΩ
MAX5400/MAX5401
256-Tap SOT-PoT
Low-Drift Digital Potentiometers in SOT23
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 = VDDand 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.
PARAMETERSYMBOLCONDITIONSMINTYPMAXUNITS
DIGITAL INPUTSInput High VoltageVIHVCC = 5V0.7 ✕ VDDV
Input Low VoltageVILVCC = 5V0.3 ✕ VDDV
Input High VoltageVIHVCC = 3V0.7 ✕ VDDV
Input Low VoltageVILVCC = 3V0.3 ✕ VDDV
Input Leakage Current±1.0μA
Input Capacitance5.0pF
TIMING CHARACTERISTICS (Voltage Divider Mode)MAX5400 (to 50% of final value, from code 0
to code 128)300
Wiper Settling TimetILMAX5401 (to 50% of final value, from code 0
to code 128)600
TIMING CHARACTERISTICS (Digital) (Note 5)SCLK Clock PeriodtCP100ns
SCLK Pulse Width HightCH40ns
SCLK Pulse Width LowtCL40ns
CS Fall to SCLK Rise Setup
TimetCSS40ns
SCLK Rise to CS Rise Hold TimetCSH0ns
DIN Setup TimetDS40ns
DIN Hold TimetDH0ns
SCLK Rise to CS Fall DelaytCS010ns
CS Rise to SCLK Rise HoldtCS140ns
CS Pulse Width HightCSW100ns
ELECTRICAL CHARACTERISTICS (continued)(VDD= +5V, VH= VDD, VL= 0, TA= TMINto 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.)
SUPPLY CURRENT
vs. TEMPERATURE
MAX5400toc09
TEMPERATURE (°C)
SUPPLY CURRENT (
VDD = +3V
VDD = +5V
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
Typical Operating Characteristics(TA = +25°C, unless otherwise noted.)
WIPER RESISTANCE vs. VOLTAGE
MAX5400 toc01
WIPER VOLTAGE (V)
WIPER RESISTANCE (
VDD = +3V
VDD = +5V
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE
MAX5400toc02
TEMPERATURE (°C)
END-TO-END RESISTANCE % CHANGE
100kΩ
50kΩ
W-to-L RESISTANCE vs. INPUT CODE
(100kΩ)
MAX5400 Toc03
INPUT CODE-DECIMAL
W-TO-L RESISTANCE (k
VDD = 2.7V
to 5.5V
W-to-L RESISTANCE vs. INPUT CODE
(50kΩ)
MAX5400 Toc04
INPUT CODE-DECIMAL
W-TO-L RESISTANCE (k
VDD = 2.7V
to 5.5V
VARIABLE RESISTOR DNL
vs. INPUT CODE (50kΩ)
MAX5400 Toc05
INPUT CODE-DECIMAL
(LSB)
VARIABLE RESISTOR INL vs. INPUT CODE
(50kΩ)
MAX5400 Toc06
INPUT CODE-DECIMAL
(LSB)
VARIABLE RESISTOR DNL
vs. INPUT CODE (100kΩ)
MAX5400 Toc07
INPUT CODE-DECIMAL
(LSB)
VARIABLE RESISTOR INL
vs. INPUT CODE (100kΩ)
MAX5400 Toc08
INPUT CODE-DECIMAL
(LSB)
MAX5400/MAX5401
256-Tap SOT-PoT
Low-Drift Digital Potentiometers in SOT23MAX5400 Toc10
TAP-to-TAP SWITCHING TRANSIENT
(FROM CODE 127 toc CODE 128)10mV/div
2.5V
5V/div
VW-L
SUPPLY CURRENT vs.
INPUT LOGIC VOLTAGE
MAX5400 Toc11
DIGITAL INPUT VOLTAGE (V)
SUPPLY CURRENT (mA)
VDD = +5V
VDD = +3V
ypical Operating Characteristics (continued)(TA = +25°C, unless otherwise noted.)
VOLTAGE DIVIDER DNL
vs. INPUT CODE (50kΩ)
MAX5400 Toc12
INPUT CODE-DECIMAL
(LSB)
VOLTAGE DIVIDER INL
vs. INPUT CODE (50kΩ)
MAX5400 Toc13
INPUT CODE-DECIMAL
(LSB)
VDD = +2.7V to +5.5V
PINNAMEFUNCTIONLLow Terminal of ResistorGNDGroundCSChip Select InputDINSerial Data InputSCLKClock Input
6VDDPower Supply. Bypass with a 0.1μF capacitor to GND.WWiper TerminalHHigh Terminal of Resistor
Pin Description
MAX5400/MAX5401
256-Tap SOT-PoT,
Low-Drift Digital Potentiometers in SOT23
Detailed DescriptionThe 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 CSis 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 CSis 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 CSis 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
MSBLSBD1D2D3D4D5D6D7
8TH CLOCK PULSE
TIME
Figure 2. Serial Interface Timing Diagram
SCLK
DIN
tCSOtCSS
tCLtCH
tDS
tDH
tCPtCSH
tCS1
tCSWCS
Figure 3. Detailed Serial Interface Timing Diagram
