General Description
The MAX5477/MAX5478/MAX5479 nonvolatile, dual,
linear-taper, digital potentiometers perform the function
of a mechanical potentiometer, but replace the
mechanics with a simple 2-wire digital interface. Each
device performs the same function as a discrete potentiometer or variable resistor and has 256 tap points.
The devices feature an internal, nonvolatile EEPROM
used to store the wiper position for initialization during
power-up. A write-protect feature prevents accidental
overwrites of the EEPROM. The fast-mode I2C-compatible serial interface allows communication at data rates
up to 400kbps, minimizing board space and reducing
interconnection complexity in many applications. Three
address inputs allow a total of eight unique address
combinations.
The MAX5477/MAX5478/MAX5479 provide three nominal resistance values: 10kΩ (MAX5477), 50kΩ
(MAX5478), or 100kΩ (MAX5479). The nominal resistor
temperature coefficient is 35ppm/°C end-to-end and
5ppm/°C ratiometric. The low temperature coefficient
makes the devices ideal for applications requiring a lowtemperature-coefficient variable resistor, such as lowdrift, programmable gain-amplifier circuit configurations.
The MAX5477/MAX5478/MAX5479 are available in 16pin 3mm x 3mm x 0.8mm thin QFN and 14-pin 4.4mm x
5mm TSSOP packages. These devices operate over
the extended -40°C to +85°C temperature range.
Applications
Mechanical Potentiometer Replacement
Low-Drift Programmable-Gain Amplifiers
Volume Control
Liquid-Crystal Display (LCD) Contrast Control
Features
♦ Power-On Recall of Wiper Position from
Nonvolatile Memory
♦ EEPROM Write Protection
♦ Tiny 3mm x 3mm x 0.8mm Thin QFN Package
♦ 35ppm/°C End-to-End Resistance Temperature
Coefficient
♦ 5ppm/°C Ratiometric Temperature Coefficient
♦ Fast 400kbps I2C†-Compatible Serial Interface
♦ 1µA (max) Static Supply Current
♦ Single-Supply Operation: +2.7V to +5.25V
♦ 256 Tap Positions per Potentiometer
♦ ±0.5 LSB DNL in Voltage-Divider Mode
♦ ±1 LSB INL in Voltage-Divider Mode
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
________________________________________________________________ Maxim Integrated Products 1
MAX5477
MAX5478
MAX5479
8-BIT
SHIFT
REGISTER
POR
16-BIT
LATCH
16-BIT
NV
MEMORY
SDA
SCL
WP
A0
A1
A2
8
256
POSITION
DECODER
8
8
256
256
POSITION
DECODER
256
HA
WA
LA
HB
WB
LB
V
DD
GND
I2C
INTERFACE
Ordering Information/Selector Guide
Functional Diagram
19-3379; Rev 2; 12/04
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.
Pin Configurations appear at end of data sheet.
†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.
PART TEMP RANGE PIN-PACKAGE
END-TO-END
RESISTANCE (kΩ)
TOP
MARK
PACKAGE CODE
MAX5477ETE* -40°C to +85°C 16 Thin QFN 10 ABO T1633F-3
MAX5477EUD* -40°C to +85°C 14 TSSOP 10 — —
MAX5478ETE* -40°C to +85°C 16 Thin QFN 50 ABP T1633F-3
MAX5478EUD -40°C to +85°C 14 TSSOP 50 — —
MAX5479ETE* -40°C to +85°C 16 Thin QFN 100 ABQ T1633F-3
MAX5479EUD -40°C to +85°C 14 TSSOP 100 — —
*Future product—contact factory for availability.
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VDD= +2.7V to +5.25V, H_ = VDD, L_ = GND, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VDD= +5V, TA=
+25°C.) (Note 1)
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.
SDA, SCL, VDDto GND.........................................-0.3V to +6.0V
All Other Pins to GND.................................-0.3V to (V
DD
+ 0.3V)
Maximum Continuous Current into H_, L_, and W_
MAX5477......................................................................
±5.0mA
MAX5478......................................................................±1.3mA
MAX5479......................................................................±0.6mA
Continuous Power Dissipation (T
A
= +70°C)
16-Pin Thin QFN (derate 17.5mW/°C above +70°C) 1399mW
14-Pin TSSOP (derate 9.1mW/°C above +70°C) .........727mW
Operating Temperature Range ...........................-40°C to +85°C
Maximum 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 256
Taps
Integral Nonlinearity INL (Note 2) ±1 LSB
Differential Nonlinearity DNL (Note 2) ±0.5 LSB
Dual Code Matching
±1 LSB
End-to-End Resistance
Temperature Coefficient
TC
R
35
ppm/°C
Ratiometric Resistance
Temperature Coefficient
5
ppm/°C
MAX5477 -3
MAX5478 -0.6
Full-Scale Error
MAX5479 -0.3
LSB
MAX5477 3
MAX5478 0.6Zero-Scale Error
MAX5479 0.3
LSB
DC PERFORMANCE (VARIABLE-RESISTOR MODE)
V
DD
= 3V ±3
Integral Nonlinearity (Note 3) INL
V
DD
= 5V ±1.5
LSB
V
DD
= 3V, MAX5477, guaranteed
monotonic
±1
VDD = 3V, MAX5478 ±1
VDD = 3V, MAX5479 ±1
Differential Nonlinearity (Note 3) DNL
V
DD
= 5V ±1
LSB
Dual Code Matching
R0 and R1 set to same code
(all codes), V
DD
= 3V or 5V
±3 LSB
DC PERFORMANCE (RESISTOR CHARACTERISTICS)
Wiper Resistance R
W
(Note 4) 325 675 Ω
Wiper Capacitance C
W
10 pF
MAX5477 7.5 10 12.5
MAX5478 37.5 50 62.5End-to-End Resistance R
HL
MAX5479 75 100 125
kΩ
R0 and R1 set to same code (all codes)
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VDD= +2.7V to +5.25V, H_ = VDD, L_ = GND, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VDD= +5V, TA=
+25°C.) (Note 1)
PARAMETER
CONDITIONS MIN TYP MAX
UNITS
DIGITAL INPUTS
VDD = 3.4V to 5.25V 2.4
Input High Voltage (Note 5) V
IH
VDD < 3.4V
V
Input Low Voltage V
IL
(Note 5) 0.8 V
Output Low Voltage V
OL
I
SINK
= 3mA 0.4 V
WP Pullup Resistance I
WP
255 kΩ
Input Leakage Current I
LEAK
±1 µA
Input Capacitance 5pF
DYNAMIC CHARACTERISTICS
Crosstalk
HA = 1kHz (0 to V
DD
), LA = GND,
LB = GND, measure WB
-80 dB
MAX5478 100
3dB Bandwidth (Note 6)
MAX5479 50
kHz
Total Harmonic Distortion Plus
Noise
H_ = 1V
RMS
, f = 1kHz, L_ = GND,
measure W_
%
NONVOLATILE MEMORY RELIABILITY
Data Retention TA = +85°C 50
Years
TA = +25°C
Endurance
T
A
= +85°C
Stores
POWER SUPPLY
Power-Supply Voltage V
DD
2.70 5.25 V
Writing to EEPROM, digital inputs at
GND or V
DD
(Note 7)
250 400
15 20.6
Supply Current I
DD
Normal operation, digital
inputs at GND or V
DD
WP = V
DD
0.5 1
µA
TIMING CHARACTERISTICS
(VDD= +2.7V to +5.25V, H_ = VDD, L_ = GND, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VDD= +5V,
T
A
= +25°C. See Figure 1.) (Notes 8 and 9)
SYMBOL
THD+N
0.7 x V
DD
0.003
200,000
50,000
ANALOG SECTION
Wiper Settling Time (Note 10) t
DIGITAL SECTION
SCL Clock Frequency f
Setup Time for START Condition t
Hold Time for START Condition t
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
SU:STA
HD:STA
WP = GND
WS
SCL
MAX5478 500
MAX5479 1000
0.6 µs
0.6 µs
400 kHz
ns
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
4 _______________________________________________________________________________________
Note 1: All devices are production tested at TA= +25°C and are guaranteed by design and characterization for -40°C < TA< +85°C.
Note 2: The DNL and INL are measured with the potentiometer configured as a voltage-divider with H_ = V
DD
and L_ = GND. The
wiper terminal is unloaded and measured with a high-input-impedance voltmeter.
Note 3: The DNL and INL are measured with the potentiometer configured as a variable resistor. H_ is unconnected and L_ =
GND. For V
DD
= +5V, the wiper is driven with 400µA (MAX5477), 80µA (MAX5478), or 40µA (MAX5479). For VDD= +3V,
the wiper is driven with 200µA (MAX5477), 40µA (MAX5478), or 20µA (MAX5479).
Note 4: The wiper resistance is measured using the source currents given in Note 3.
Note 5: The devices draw current in excess of the specified supply current when the digital inputs are driven with voltages between
(V
DD
- 0.5V) and (GND + 0.5V). See Supply Current vs. Digital Input Voltage in the Typical Operating Characteristics.
Note 6: Wiper at midscale with a 10pF load (DC measurement). L_ = GND, an AC source is applied to H_, and the W_ output is
measured. A 3dB bandwidth occurs when the AC W_/H_ value is 3dB lower than the DC W_/H_ value.
Note 7: The programming current exists only during power-up and EEPROM writes.
Note 8: The SCL clock period includes rise and fall times (t
R
= tF). All digital input signals are specified with tR= tF= 2ns and
timed from a voltage level of (V
IL
+ VIH) / 2.
Note 9: Digital timing is guaranteed by design and characterization, and is not production tested.
Note 10: This is measured from the STOP pulse to the time it takes the output to reach 50% of the output step size (divider mode). It
is measured with a maximum external capacitive load of 10pF.
Note 11: An appropriate bus pullup resistance must be selected depending on board capacitance. Refer to the I
2
C-bus specifica-
tion document linked to this web address: www.semiconductors.philips.com/acrobat/literature/9398/39340011.pdf
Note 12: The idle time begins from the initiation of the STOP pulse.
PARAMETER
CONDITIONS
UNITS
SCL High Time t
HIGH
0.6 µs
SCL Low Time t
LOW
1.3 µs
Data Setup Time
100 ns
Data Hold Time
0 0.9 µs
SDA, SCL Rise Time t
R
300 ns
SDA, SCL Fall Time t
F
300 ns
Setup Time for STOP Condition
0.6 µs
Bus Free Time Between STOP
and START Condition
t
BUF
Minimum power-up rate = 0.2V/µs 1.3 µs
Pulse Width of Spike Suppressed
t
SP
50 ns
Capacitive Load for Each Bus
Line
C
B
(Note 11) 400 pF
Write NV Register Busy Time (Note 12) 12 ms
TIMING CHARACTERISTICS (continued)
(VDD= +2.7V to +5.25V, H_ = VDD, L_ = GND, TA= -40°C to +85°C, unless otherwise noted. Typical values are at VDD= +5V,
T
A
= +25°C. See Figure 1.) (Notes 8 and 9)
SYMBOL
t
SU:DAT
t
HD:DAT
t
SU:STO
MIN TYP MAX
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
_______________________________________________________________________________________ 5
SUPPLY CURRENT
vs. TEMPERATURE
MAX5477/78/79 toc01
TEMPERATURE (°C)
SUPPLY CURRENT (µA)
603510-15
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
0
-40 85
VDD = 5V
VDD = 3V
0
100
50
200
150
300
250
350
450
400
500
0649632 128 160 192 224 256
WIPER RESISTANCE
vs. INPUT CODE
MAX5477/78/79 toc02
INPUT CODE
WIPER RESISTANCE (Ω)
TAP-TO-TAP SWITCHING TRANSIENT
MAX5477/78/79 toc03
1µs/div
SDA
2V/div
W_
20mV/div
MAX5478
C
L
= 10pF
H_ = V
DD
FROM TAP 00 TO TAP 04
TAP-TO-TAP SWITCHING TRANSIENT
MAX5477/78/79 toc04
400ns/div
SDA
2V/div
W_
20mV/div
MAX5479
C
W_
= 10pF
H_ = V
DD
FROM TAP 00 TO TAP 04
WIPER TRANSIENT AT POWER-ON
MAX5477/78/79 toc05
4µs/div
V
DD
2V/div
W_
1V/div
MAX5478
TAP = 128
WIPER TRANSIENT AT POWER-ON
MAX5477/78/79 toc06
2µs/div
V
DD
2V/div
W_
1V/div
MAX5479
TAP = 128
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
06432 96 128 160 192 224 256
INTEGRAL NONLINEARITY
vs. CODE (VDM MODE)
MAX5477/78/79 toc07
CODE
INL (LSB)
MAX5478
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
06432 96 128 160 192 224 256
DIFFERENTIAL NONLINEARITY
vs. CODE (VDM MODE)
MAX5477/78/79 toc08
CODE
DNL (LSB)
MAX5478
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
06432 96 128 160 192 224 256
INTEGRAL NONLINEARITY
vs. CODE (VRM MODE)
MAX5477/78/79 toc09
CODE
INL (LSB)
MAX5478
Typical Operating Characteristics
(VDD= +5V, H_ = VDD, L_ = GND, TA= +25°C, unless otherwise noted.)
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
6 _______________________________________________________________________________________
-0.10
-0.08
-0.04
0
0.02
0.06
0.10
06432 96 128 160 192 224 256
DIFFERENTIAL NONLINEARITY
vs. CODE (VRM MODE)
MAX5477/78/79 toc10
CODE
DNL (LSB)
-0.06
-0.02
0.08
0.04
MAX5478
-0.20
-0.12
-0.16
-0.04
-0.08
0.04
0
0.08
0.16
0.12
0.20
0649632 128 160 192 224 256
INTEGRAL NONLINEARITY
vs. CODE (VDM MODE)
MAX5477/78/79 toc11
CODE
INL (LSB)
MAX5479
-0.14
-0.02
-0.04
-0.06
-0.08
-0.10
-0.12
0
0.04
0.02
0.10
0.08
0.12
0.06
0.14
06432 96 128 160 192 224 256
DIFFERENTIAL NONLINEARITY
vs. CODE (VDM MODE)
MAX5477/78/79 toc12
CODE
DNL (LSB)
MAX5479
-0.20
-0.12
-0.16
-0.04
-0.08
0.04
0
0.08
0.16
0.12
0.20
0649632 128 160 192 224 256
INTEGRAL NONLINEARITY
vs. CODE (VRM MODE)
MAX5477/78/79 toc13
CODE
INL (LSB)
MAX5479
-0.20
-0.12
-0.16
-0.04
-0.08
0.04
0
0.08
0.16
0.12
0.20
0649632 128 160 192 224 256
DIFFERENTIAL NONLINEARITY
vs. CODE (VRM MODE)
MAX5477/78/79 toc14
CODE
DNL (LSB)
MAX5479
CROSSTALK vs. FREQUENCY (MAX5478)
MAX5477/78/79 toc15
FREQUENCY (kHz)
CROSSTALK (dB)
1001010.1
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-100
0.01 1000
CW_ = 10pF
TAP = 0
CROSSTALK vs. FREQUENCY (MAX5479)
MAX5477/78/79 toc16
FREQUENCY (kHz)
CROSSTALK (dB)
1000100101
-90
-80
-70
-60
-50
-40
-30
-20
-10
0
-100
0.1 10,000
CW_ = 10pF
TAP = 128
Typical Operating Characteristics (continued)
(VDD= +5V, H_ = VDD, L_ = GND, TA= +25°C, unless otherwise noted.)
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
_______________________________________________________________________________________ 7
MIDSCALE WIPER RESPONSE
vs. FREQUENCY (MAX5478)
MAX5477 toc17
FREQUENCY (kHz)
GAIN (dB)
100101
-7
-6
-5
-4
-3
-2
-1
0
1
2
-8
0.1 1000
CW_ = 50pF
C
W_
= 10pF
MIDSCALE WIPER RESPONSE
vs. FREQUENCY (MAX5479)
MAX5477/78/79 toc18
FREQUENCY (kHz)
GAIN (dB)
100101
-4
-3
-2
-1
0
1
2
-5
0.1 1000
CW_ = 50pF
C
W_
= 10pF
THD+N vs. FREQUENCY
(MAX5478)
MAX5477 toc19
FREQUENCY (kHz)
THD+N (%)
1010.1
0.001
0.01
0.1
1
10
0.0001
0.01 100
MIDSCALE
THD+N vs. FREQUENCY
(MAX5479)
MAX5477 toc20
FREQUENCY (kHz)
THD+N (%)
1010.1
0.001
0.01
0.1
1
10
0.0001
0.01 100
MIDSCALE
-0.5
-0.2
-0.3
-0.4
-0.1
0
0.1
0.2
0.3
0.4
0.5
-40 10-15 356085
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE (MAX5478)
MAX5477/78/79 toc21
TEMPERATURE (°C)
END-TO-END RESISTANCE CHANGE (%)
-0.5
-0.2
-0.3
-0.4
-0.1
0
0.1
0.2
0.3
0.4
0.5
-40 10-15 35 60 85
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE (MAX5479)
MAX5477/78/79 toc22
TEMPERATURE (°C)
END-TO-END RESISTANCE CHANGE (%)
0
350
300
250
400
450
550
500
600
0 1.00.5 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
SUPPLY CURRENT
vs. DIGITAL INPUT VOLTAGE
MAX5477/78/79 toc23
DIGITAL INPUT VOLTAGE (V)
SUPPLY CURRENT (µA)
WP = GND
VCC = 5V
VCC = 3V
200
150
100
50
Typical Operating Characteristics (continued)
(VDD= +5V, H_ = VDD, L_ = GND, TA= +25°C, unless otherwise noted.)
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
8 _______________________________________________________________________________________
Pin Description
PIN
TSSOP
FUNCTION
1 15 HA Potentiometer A High Terminal
2 14 WA Potentiometer A Wiper Terminal
3 13 LA Potentiometer A Low Terminal
4 12 HB Potentiometer B High Terminal
5 11 WB Potentiometer B Wiper Terminal
6 10 LB Potentiometer B Low Terminal
79WP
Write-Protect Input. Connect to GND to allow changes to the wiper position and the data stored
in the EEPROM. Connect to V
DD
or leave open to enable the write protection of the EEPROM.
87
Ground
9 6 A2 Address Input 2. Connect to VDD or GND (see Table 1).
10 5 A1 Address Input 1. Connect to VDD or GND (see Table 1).
11 4 A0 Address Input 0. Connect to VDD or GND (see Table 1).
12 3
I2C Serial Data
13 2
I2C Clock Input
14 1
Power-Supply Input. Connect a +2.7V to +5.25V power supply to VDD and bypass VDD to GND
with a 0.1µF capacitor installed as close to the device as possible.
— 8, 16
No Connection. Do not connect.
— EP EP Exposed Paddle. Do not connect.
Detailed Description
The MAX5477/MAX5478/MAX5479 contain two resistor
arrays with 255 elements in each array. The MAX5477
has a total end-to-end resistance of 10kΩ, the
MAX5478 has an end-to-end resistance of 50kΩ, and
the MAX5479 has an end-to-end resistance of 100kΩ.
The MAX5477/MAX5478/MAX5479 provide access to
the high, low, and wiper terminals for a standard voltage-divider configuration. Connect H_, L_, and W_ in
any desired configuration as long as their voltages
remain between GND and VDD.
Figure 1. I2C Serial-Interface Timing Diagram
THIN QFN
NAME
GND
SDA
SCL
V
DD
N.C.
SDA
t
SU:DAT
t
t
t
LOW
HD:DAT
SU:STA
t
HD:STA
t
SU:STO
t
BUF
SCL
t
t
HD:STA
START
CONDITION
(S)
PARAMETERS ARE MEASURED FROM 30% TO 70%.
HIGH
t
R
t
F
REPEATED START
CONDITION
(SR)
ACKNOWLEDGE
(A)
STOP
CONDITION
(P)
START
CONDITION
(S)
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
_______________________________________________________________________________________ 9
A simple 2-wire I2C-compatible serial interface moves
the wiper among the 256 tap points (Figure 2). A nonvolatile memory stores the wiper position and recalls
the stored wiper position upon power-up. The nonvolatile memory is guaranteed for 50 years for wiper
data retention and up to 200,000 wiper store cycles.
Analog Circuitry
The MAX5477/MAX5478/MAX5479 consist of two resistor
arrays with 255 resistive elements; 256 tap points are
accessible to the wipers, along the resistor string
between H_ and L_. The wiper tap point is selected by
programming the potentiometer through the I2C interface. An address byte, a command byte, and 8 data bits
program the wiper position for each potentiometer. The
H_ and L_ terminals of the MAX5477/MAX5478/
MAX5479 are similar to the two end terminals of a
mechanical potentiometer. The MAX5477/MAX5478/
MAX5479 feature power-on reset circuitry that loads the
wiper position from the nonvolatile memory at power-up.
Digital Interface
The MAX5477/MAX5478/MAX5479 feature an internal,
nonvolatile EEPROM that stores the wiper state for initialization during power-up. The shift register decodes
the command and address bytes, routing the data to
the proper memory registers. Data written to a volatile
memory register immediately updates the wiper position, or writes data to a nonvolatile register for storage
(see Table 2).
The volatile register retains data as long as the device
is powered. Removing power clears the volatile register. The nonvolatile register retains data even after
power is removed. Upon power-up, the power-on reset
circuitry controls the transfer of data from the nonvolatile register to the volatile register.
A write-protect feature prevents accidental overwriting
of the EEPROM. Connect WP to VDDor leave open to
prevent any EEPROM write cycles. The wiper register
only updates with the value in the EEPROM when WP =
SDA
SCL
S
START
CONDITION
P
STOP
CONDITION
Figure 3. Start and Stop Conditions
MSBSTART
SCL
SDA ACKA0A2 A11010
LSB
NOP/W
Figure 4. Slave Address
256-POSITION
DECODER
H_
L_
R
255
S
255
S
254
S
3
S
2
S
1
S
256
R
254
R
2
R
1
W_
R
W
WIPER
CODE 02h
Figure 2. Potentiometer Configuration
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
10 ______________________________________________________________________________________
VDD. Connect WP to GND to allow write commands to
the EEPROM and to update the wiper position from
either the value in the EEPROM or directly from the I
2
C
interface. Connecting WP to GND increases the supply
current by 19.6µA (max).
Serial Addressing
The MAX5477/MAX5478/MAX5479 operate as slave
devices that send and receive data through an I
2
C-/
SMBus™-compatible 2-wire serial interface. The interface uses a serial data access (SDA) line and a serial
clock line (SCL) to achieve bidirectional communication
between master(s) and slave(s). A master, typically a
microcontroller, initiates all data transfers to the
MAX5477/MAX5478/MAX5479, and generates the SCL
clock that synchronizes the data transfer (Figure 1).
The MAX5477/MAX5478/MAX5479 SDA line operates
as both an input and an open-drain output. The SDA
line requires a pullup resistor, typically 4.7kΩ. The
MAX5477/MAX5478/MAX5479 SCL line operates only
as an input. The SCL line requires a pullup resistor (typically 4.7kΩ) if there are multiple masters on the 2-wire
interface, or if the master in a single-master system has
an open-drain SCL output. SCL and SDA should not
exceed VDDin a mixed-voltage system, despite the
open-drain drivers.
Each transmission consists of a START (S) condition
(Figure 3) sent by a master, followed by the
MAX5477/MAX5478/MAX5479 7-bit slave address plus
the NOP/W bit (Figure 4), 1 command byte and 1 data
byte, and finally a STOP (P) condition (Figure 3).
Start and Stop Conditions
Both SCL and SDA remain high when the interface is
not busy. A master controller signals the beginning of a
transmission with a START condition by transitioning
SDA from high to low while SCL is high. The master
controller issues a STOP condition by transitioning the
SDA from low to high while SCL is high, when it finishes
communicating with the slave. The bus is then free for
another transmission (Figure 3).
Bit Transfer
One data bit is transferred during each clock pulse.
The data on the SDA line must remain stable while SCL
is high (Figure 5).
Acknowledge
The acknowledge bit is a clocked 9th bit that the recipient
uses to handshake receipt of each byte of data (Figure
6). Thus, each byte transferred effectively requires 9 bits.
The master controller generates the 9th clock pulse, and
the recipient pulls down SDA during the acknowledge
clock pulse, so the SDA line remains stable low during
the high period of the clock pulse.
Slave Address
The MAX5477/MAX5478/MAX5479 have a 7-bit-long
slave address (Figure 4). The 8th bit following the 7-bit
ADDRESS INPUTS
A2 A1 A0
SLAVE ADDRESS
GND GND GND 0101000
GND GND V
DD
0101001
GND V
DD
GND 0101010
GND V
DD
V
DD
0101011
V
DD
GND GND 0101100
V
DD
GND V
DD
0101101
V
DD
V
DD
GND 0101110
V
DD
V
DD
V
DD
0101111
Figure 5. Bit Transfer
1
SCL
START
CONDITION
SDA
289
CLOCK PULSE FOR
ACKNOWLEDGMENT
ACKNOWLEDGE
NOT ACKNOWLEDGE
Figure 6. Acknowledge
SMBus is a trademark of Intel Corporation.
Table 1. Slave Addresses
SDA
SCL
DATA STABLE,
DATA VALID
CHANGE OF
DATA ALLOWED
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
______________________________________________________________________________________ 11
slave address is the NOP/W bit. Set the NOP/W bit low for
a write command and high for a no-operation command.
The MAX5477/MAX5478/MAX5479 provide three
address inputs (A0, A1, and A2), allowing up to eight
devices to share a common bus (Table 1). The first 4
bits (MSBs) of the MAX5477/MAX5478/MAX5479 slave
addresses are always 0101. A2, A1, and A0 set the next
3 bits in the slave address. Connect each address input
to VDDor GND to set these 3 bits. Each device must
have a unique address to share a common bus.
Message Format for Writing
Write to the MAX5477/MAX5478/MAX5479 by transmitting the device’s slave address with NOP/W (8th bit) set
to zero, followed by at least 1 byte of information
(Figure 7). The 1st byte of information is the command
byte. The bytes received after the command byte are
the data bytes. The 1st data byte goes into the internal
register of the MAX5477/MAX5478/MAX5479 as selected by the command byte (Figure 8).
Command Byte
Use the command byte to select the source and destination of the wiper data (nonvolatile or volatile memory
registers) and swap data between nonvolatile and
volatile memory registers (see Table 2).
Command Descriptions
VREG: The data byte writes to the volatile memory register and the wiper position updates with the data in the
volatile memory register.
NVREG: The data byte writes to the nonvolatile memory
register. The wiper position is unchanged.
NVREGxVREG: Data transfers from the nonvolatile
memory register to the volatile memory register (wiper
position updates).
VREGxNVREG: Data transfers from the volatile memory
register into the nonvolatile memory register.
Nonvolatile Memory
The internal EEPROM consists of a 16-bit nonvolatile
register that retains the value written to it prior to power
down. The nonvolatile register is programmed with the
midscale value at the factory. The nonvolatile memory
is guaranteed for 50 years for wiper position retention
and up to 200,000 wiper write cycles. A write-protect
feature prevents accidental overwriting of the EEPROM.
Connect WP to V
DD
or leave open to enable the writeprotect feature. The wiper position only updates with
the value in the EEPROM when WP = VDD. Connect WP
to GND to allow EEPROM write cycles and to update
the wiper position from nonvolatile memory or directly
from the I2C serial interface.
Power-Up
Upon power-up, the MAX5477/MAX5478/MAX5479
load the data stored in the nonvolatile memory register
into the volatile memory register, updating the wiper
position with the data stored in the nonvolatile memory
register. This initialization period takes 10µs.
A
0SLAVE ADDRESS COMMAND BYTE DATA BYTE
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
NOP/W
1 BYTE
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
D15 D14 D13 D12 D11 D10 D9 D8 D1 D0D3 D2D5 D4D7 D6
HOW CONTROL BYTE AND DATA BYTE MAP INTO
MAX5477/MAX5478/MAX5479 REGISTERS
S AA
P
Figure 7. Command Byte Received
Figure 8. Command and Single Data Byte Received
COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
D15 D14 D13 D12 D11 D10 D9 D8
S A0SLAVE ADDRESS COMMAND BYTE
NOP/W
AP
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
12 ______________________________________________________________________________________
ADDRESS BYTE COMMAND BYTE DATA BYTE
SCL CYCLE
NUMBER
NOTES
VREG
NVREG
NVREGxVREG
VREGxNVREG
WIPER A
ONLY
VREG
NVREG
NVREGxVREG
VREGxNVREG
WIPER B
ONLY
VREG
NVREG
NVREGxVREG
VREGxNVREG
WIPERS
A AND B
Table 2. Command Byte Summary
Standby
The MAX5477/MAX5478/MAX5479 feature a low-power
standby mode. When the device is not being programmed, it enters into standby mode and supply current drops to 500nA (typ).
Applications Information
The MAX5477/MAX5478/MAX5479 are ideal for circuits
requiring digitally controlled adjustable resistance,
such as LCD contrast control (where voltage biasing
adjusts the display contrast), or for programmable filters with adjustable gain and/or cutoff frequency.
Positive LCD Bias Control
Figures 9 and 10 show an application where the
MAX5477/MAX5478/MAX5479 provide an adjustable,
positive LCD bias voltage. The op amp provides buffer-
ing and gain to the resistor-divider network made by
the potentiometer (Figure 9) or by a fixed resistor and a
variable resistor (see Figure 10).
Programmable Filter
Figure 11 shows the MAX5477/MAX5478/MAX5479 in a
1st-order programmable application filter. Adjust the
gain of the filter with R2, and set the cutoff frequency
with R
3
. Use the following equations to calculate the
gain (A) and the -3dB cutoff frequency (fC):
A
R
R
f
RC
C
=+
=
××
1
1
2
1
2
3
π
V
OUT
30V
5V
W_
H_
L_
MAX5477
MAX5478
MAX5479
MAX480
Figure 9. Positive LCD Bias Control Using a Voltage-Divider
Figure 10. Positive LCD Bias Control Using a Variable Resistor
1 2 3 4 5 6 7 8 9 10111213 14151617 18 1920 21222324 2526 27
START
(S)
A6 A5 A4 A3 A2 A1 A0
0101A2A1A00 00010001 D7D6D5D4D3D2D1D0
0101A2A1A00 00100001 D7D6D5D4D3D2D1D0
0101A2A1A00 01100001 D7D6D5D4D3D2D1D0
0101A2A1A00 01010001 D7D6D5D4D3D2D1D0
0101A2A1A00 00010010 D7D6D5D4D3D2D1D0
0101A2A1A00 00100010 D7D6D5D4D3D2D1D0
0101A2A1A00 01100010 D7D6D5D4D3D2D1D0
0101A2A1A00 01010010 D7D6D5D4D3D2D1D0
0101A2A1A00 00010011 D7D6D5D4D3D2D1D0
0101A2A1A00 00100011 D7D6D5D4D3D2D1D0
0101A2A1A00 01100011 D7D6D5D4D3D2D1D0
0101A2A1A00 01010011 D7D6D5D4D3D2D1D0
ACK
(A)
TX NV V R3 R2 R1 R0
ACK
D7 D6 D5 D4 D3 D2 D1 D0
(A)
ACK
(A)
STOP
(P)
5V
30V
V
H_
MAX5477
MAX5478
MAX5479
W_
L_
MAX480
OUT
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
______________________________________________________________________________________ 13
Offset Voltage and Gain Adjustment
Connect the high and low terminals of one potentiometer of a MAX5477 between the NULL inputs of a
MAX410 and the wiper to the op amp’s positive supply
to nullify the offset voltage over the operating temperature range. Install the other potentiometer in the feedback path to adjust the gain of the MAX410 (Figure 12).
Adjustable Voltage Reference
Figure 13 shows the MAX5477/MAX5478/MAX5479
used as the feedback resistors in multiple adjustable
voltage reference applications. Independently adjust
the output voltages of the MAX6160 parts from 1.23V to
V
IN
- 0.2V by changing the wiper positions of the
MAX5477/MAX5478/MAX5479.
MAX6160
IN
5V
OUT
ADJ
GND
HA
LA
WA
V
OUT1
IN
OUT
ADJ
GND
HB
LB
WB
V
OUT2
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
MAX6160
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
FOR THE MAX5477
V
OUT_
= 1.23V x
10kΩ
R
FOR THE MAX5478
V
OUT_
= 1.23V x
50kΩ
R
FOR THE MAX5479
V
OUT_
= 1.23V x
100kΩ
R
WHERE R = RHL x D / 256
AND D = DECIMAL VALUE OF WIPER CODE
RR
Figure 13. Adjustable Voltage Reference
3
2
5V
7
4
1
6
8
MAX410
HA
LA
WA
R2
R1
HB
LB
WB
1/2 MAX5477
1/2 MAX5477
R2 = RHL x D / 256
WHERE R
HL
= END-TO-END RESISTANCE
AND = D DECIMAL VALUE OF WIPER CODE
Figure 12. Offset Voltage Adjustment Circuit
MAX5477
MAX5478
MAX5479
V
IN
R
2
HB
WB
LB
R
1
V
OUT
R
3
HA
WA
LA
C
MAX410
V+
V-
R
2
, R3 = RHL x D / 256
WHERE R
HL
= END-TO-END RESISTANCE
AND D = DECIMAL VALUE OF WIPER CODE
Figure 11. Programmable Filter
16
1
2
3
4
12
11
10
9
15 14 13
5678
N.C.
HA
WA L A
HB
WB
LB
WP
SCL
SDA
A0
A1
A2
GND
N.C.
V
DD
TOP VIEW
MAX5477
MAX5478
MAX5479
14
13
12
11
10
9
8
1
2
3
4
5
6
7
V
DD
SCL
SDA
A0HB
LA
WA
HA
A1
A2
GNDWP
LB
WB
TSSOP
(4.4mm x 5mm)
THIN QFN
(3mm x 3mm)
MAX5477
MAX5478
MAX5479
Pin Configurations
Chip Information
TRANSISTOR COUNT: 12,651
PROCESS: BiCMOS
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
14 ______________________________________________________________________________________
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages
.)
12x16L QFN THIN.EPS
0.10 C 0.08 C
0.10 M C A B
D
D/2
E/2
E
A1
A2
A
E2
E2/2
L
k
e
(ND - 1) X e
(NE - 1) X e
D2
D2/2
b
L
e
L
C
L
e
C
L
L
C
L
C
E
1
2
21-0136
PACKAGE OUTLINE
12, 16L, THIN QFN, 3x3x0.8mm
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
EXPOSED PAD VARIATIONS
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO
JESD 95-1 SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED
WITHIN THE ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR
MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.20 mm AND 0.25 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220 REVISION C.
NOTES:
E
2
2
21-0136
PACKAGE OUTLINE
12, 16L, THIN QFN, 3x3x0.8mm
DOWN
BONDS
ALLOWED
MAX5477/MAX5478/MAX5479
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
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.
15 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2004 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.
TSSOP4.40mm.EPS
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information
go to www.maxim-ic.com/packages
.)
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