MAX5478EUD [MAXIM]
Dual, 256-Tap, Nonvolatile, I2C-Interface, Digital Potentiometers; 双路，256抽头，非易失， I²C接口，数字电位器
| 型号： | MAX5478EUD |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Dual, 256-Tap, Nonvolatile, I2C-Interface, Digital Potentiometers |
| 文件： | 总15页 (文件大小：385K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3379; Rev 2; 12/04
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
General Description
Features
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 poten-
tiometer or variable resistor and has 256 tap points.
♦ 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
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-compati-
ble 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.
♦ 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 ꢀSꢁ ꢂNꢀ in Voltage-ꢂivider Mode
1 ꢀSꢁ INꢀ in Voltage-ꢂivider Mode
The MAX5477/MAX5478/MAX5479 provide three nomi-
nal 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 low-
temperature-coefficient variable resistor, such as low-
drift, programmable gain-amplifier circuit configurations.
Functional Diagram
HA
V
DD
8-BIT
SHIFT
REGISTER
256
POSITION
DECODER
8
8
8
256
256
16-BIT
LATCH
GND
WA
POR
The MAX5477/MAX5478/MAX5479 are available in 16-
pin 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.
LA
16-BIT
NV
MEMORY
SDA
SCL
WP
HB
I2C
INTERFACE
256
POSITION
DECODER
WB
LB
MAX5477
MAX5478
MAX5479
A0
A1
A2
Applications
Mechanical Potentiometer Replacement
Low-Drift Programmable-Gain Amplifiers
Volume Control
2
†Purchase of I C components from Maxim Integrated
Products, Inc. or one of its sublicensed Associated
2
Companies, conveys a license under the Philips I C Patent
2
Liquid-Crystal Display (LCD) Contrast Control
Rights to use these components in an I C system, provided
2
that the system conforms to the I C Standard Specification as
defined by Philips.
Ordering Information/Selector Guide
ENꢂ-TO-ENꢂ
RESISTANCE (kΩ)
TOP
MARK
PART
TEMP RANGE
PIN-PACKAGE
PACKAGE COꢂE
MAX5477ETE*
MAX5477EUD*
MAX5478ETE*
MAX5478EUD
MAX5479ETE*
MAX5479EUD
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
16 Thin QFN
14 TSSOP
10
ABO
—
T1633F-3
—
10
16 Thin QFN
14 TSSOP
50
ABP
—
T1633F-3
—
50
16 Thin QFN
14 TSSOP
100
100
ABQ
—
T1633F-3
—
*Future product—contact factory for availability.
Pin Configurations appear at end of data sheet.
________________________________________________________________ Maxim Integrated Products
1
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.
2
Dual, 256-Tap, Nonvolatile, I C-Interface,
Digital Potentiometers
AꢁSOꢀUTE MAXIMUM RATINGS
SDA, SCL, V
to GND.........................................-0.3V to +6.0V
Continuous Power Dissipation (T = +70°C)
A
DD
All Other Pins to GND.................................-0.3V to (V
Maximum Continuous Current into H_, L_, and W_
MAX5477...................................................................... 5.0mA
MAX5478...................................................................... 1.3mA
MAX5479...................................................................... 0.6mA
+ 0.3V)
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
DD
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.
EꢀECTRICAꢀ CHARACTERISTICS
(V
= +2.7V to +5.25V, H_ = V , L_ = GND, T = -40°C to +85°C, unless otherwise noted. Typical values are at V
= +5V, T =
DD A
DD
DD
A
+25°C.) (Note 1)
PARAMETER
SYMꢁOꢀ
CONꢂITIONS
MIN
TYP
MAX
UNITS
ꢂC PERFORMANCE (VOꢀTAGE-ꢂIVIꢂER MOꢂE)
Resolution
256
Taps
LSB
LSB
LSB
Integral Nonlinearity
Differential Nonlinearity
Dual Code Matching
INL
(Note 2)
(Note 2)
1
0.5
1
DNL
R0 and R1 set to same code (all codes)
End-to-End Resistance
Temperature Coefficient
TC
35
5
ppm/°C
ppm/°C
R
Ratiometric Resistance
Temperature Coefficient
MAX5477
MAX5478
MAX5479
MAX5477
MAX5478
MAX5479
-3
-0.6
-0.3
3
Full-Scale Error
Zero-Scale Error
LSB
LSB
0.6
0.3
ꢂC PERFORMANCE (VARIAꢁꢀE-RESISTOR MOꢂE)
V
V
= 3V
= 5V
3
DD
DD
Integral Nonlinearity (Note 3)
Differential Nonlinearity (Note 3)
Dual Code Matching
INL
LSB
LSB
LSB
1.5
V
= 3V, MAX5477, guaranteed
DD
1
monotonic
DNL
V
V
V
= 3V, MAX5478
= 3V, MAX5479
= 5V
1
1
1
DD
DD
DD
R0 and R1 set to same code
(all codes), V = 3V or 5V
3
DD
ꢂC PERFORMANCE (RESISTOR CHARACTERISTICS)
Wiper Resistance
Wiper Capacitance
R
W
C
W
(Note 4)
325
10
675
Ω
pF
MAX5477
MAX5478
MAX5479
7.5
37.5
75
10
12.5
62.5
125
End-to-End Resistance
R
50
kΩ
HL
100
2
_______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
EꢀECTRICAꢀ CHARACTERISTICS (continued)
(V
= +2.7V to +5.25V, H_ = V , L_ = GND, T = -40°C to +85°C, unless otherwise noted. Typical values are at V
= +5V, T =
DD A
DD
DD
A
+25°C.) (Note 1)
PARAMETER
SYMꢁOꢀ
CONꢂITIONS
MIN
TYP
MAX
UNITS
ꢂIGITAꢀ INPUTS
V
V
= 3.4V to 5.25V
2.4
DD
DD
Input High Voltage (Note 5)
V
V
IH
< 3.4V
0.7 x V
DD
Input Low Voltage
V
(Note 5)
= 3mA
0.8
0.4
V
IL
Output Low Voltage
WP Pullup Resistance
Input Leakage Current
Input Capacitance
V
I
V
OL
SINK
I
255
kΩ
µA
pF
WP
I
1
LEAK
5
ꢂYNAMIC CHARACTERISTICS
HA = 1kHz (0 to V ), LA = GND,
DD
LB = GND, measure WB
Crosstalk
-80
dB
kHz
%
MAX5478
100
50
3dB Bandwidth (Note 6)
MAX5479
Total Harmonic Distortion Plus
Noise
H_ = 1V
, f = 1kHz, L_ = GND,
RMS
THD+N
0.003
measure W_
NONVOꢀATIꢀE MEMORY REꢀIAꢁIꢀITY
Data Retention
T
A
T
A
T
A
= +85°C
= +25°C
= +85°C
50
Years
200,000
50,000
Endurance
Stores
POWER SUPPꢀY
Power-Supply Voltage
V
2.70
5.25
400
V
DD
Writing to EEPROM, digital inputs at
GND or V (Note 7)
250
DD
Supply Current
I
µA
DD
WP = GND
15
20.6
1
Normal operation, digital
inputs at GND or V
DD
WP = V
0.5
DD
TIMING CHARACTERISTICS
(V
= +2.7V to +5.25V, H_ = V , L_ = GND, T = -40°C to +85°C, unless otherwise noted. Typical values are at V
= +5V,
DD
DD
DD
A
T
A
= +25°C. See Figure 1.) (Notes 8 and 9)
PARAMETER
SYMꢁOꢀ
CONꢂITIONS
MIN
TYP
MAX
UNITS
ANAꢀOG SECTION
MAX5478
MAX5479
500
Wiper Settling Time (Note 10)
t
ns
WS
1000
ꢂIGITAꢀ SECTION
SCL Clock Frequency
f
400
kHz
µs
SCL
Setup Time for START Condition
Hold Time for START Condition
t
0.6
0.6
SU:STA
HD:STA
t
µs
_______________________________________________________________________________________
3
2
Dual, 256-Tap, Nonvolatile, I C-Interface,
Digital Potentiometers
TIMING CHARACTERISTICS (continued)
(V
= +2.7V to +5.25V, H_ = V , L_ = GND, T = -40°C to +85°C, unless otherwise noted. Typical values are at V
= +5V,
DD
DD
A
DD
T
A
= +25°C. See Figure 1.) (Notes 8 and 9)
PARAMETER
SYMꢁOꢀ
CONꢂITIONS
MIN
0.6
1.3
100
0
TYP
MAX
UNITS
µs
SCL High Time
t
HIGH
SCL Low Time
t
µs
LOW
Data Setup Time
t
ns
SU:DAT
HD:DAT
Data Hold Time
t
0.9
300
300
µs
SDA, SCL Rise Time
SDA, SCL Fall Time
Setup Time for STOP Condition
t
ns
R
t
ns
F
t
0.6
1.3
µs
SU:STO
Bus Free Time Between STOP
and START Condition
t
Minimum power-up rate = 0.2V/µs
µs
ns
BUF
Pulse Width of Spike Suppressed
t
SP
50
400
12
Capacitive Load for Each Bus
Line
C
(Note 11)
(Note 12)
pF
ms
B
Write NV Register Busy Time
Note 1: All devices are production tested at T = +25°C and are guaranteed by design and characterization for -40°C < T < +85°C.
A
A
Note 2: The DNL and INL are measured with the potentiometer configured as a voltage-divider with H_ = V
wiper terminal is unloaded and measured with a high-input-impedance voltmeter.
and L_ = GND. The
DD
Note 3: The DNL and INL are measured with the potentiometer configured as a variable resistor. H_ is unconnected and L_ =
GND. For V = +5V, the wiper is driven with 400µA (MAX5477), 80µA (MAX5478), or 40µA (MAX5479). For V = +3V,
DD
DD
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 - 0.5V) and (GND + 0.5V). See Supply Current vs. Digital Input Voltage in the Typical Operating Characteristics.
DD
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 = t ). All digital input signals are specified with t = t = 2ns and
R
F
R
F
timed from a voltage level of (V + V ) / 2.
IL
IH
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 I2C-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.
4
_______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
Typical Operating Characteristics
(V
= +5V, H_ = V , L_ = GND, T = +25°C, unless otherwise noted.)
DD A
DD
WIPER RESISTANCE
vs. INPUT CODE
SUPPLY CURRENT
vs. TEMPERATURE
TAP-TO-TAP SWITCHING TRANSIENT
MAX5477/78/79 toc03
500
450
400
350
300
250
200
150
100
50
1.0
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
SDA
2V/div
V
= 5V
DD
W_
20mV/div
MAX5478
C = 10pF
V
= 3V
L
DD
H_ = V
DD
FROM TAP 00 TO TAP 04
0
0
32 64 96 128 160 192 224 256
INPUT CODE
-40
-15
10
35
60
85
1µs/div
TEMPERATURE (°C)
WIPER TRANSIENT AT POWER-ON
TAP-TO-TAP SWITCHING TRANSIENT
WIPER TRANSIENT AT POWER-ON
MAX5477/78/79 toc05
MAX5477/78/79 toc04
MAX5477/78/79 toc06
SDA
2V/div
V
V
DD
DD
2V/div
2V/div
W_
20mV/div
W_
W_
1V/div
MAX5479
1V/div
C
= 10pF
W_
MAX5478
TAP = 128
MAX5479
TAP = 128
H_ = V
DD
FROM TAP 00 TO TAP 04
4µs/div
400ns/div
2µs/div
INTEGRAL NONLINEARITY
vs. CODE (VRM MODE)
INTEGRAL NONLINEARITY
vs. CODE (VDM MODE)
DIFFERENTIAL NONLINEARITY
vs. CODE (VDM MODE)
0.3
0.2
0.1
0
0.3
0.3
0.2
0.1
0
MAX5478
MAX5478
MAX5478
0.2
0.1
0
-0.1
-0.2
-0.3
-0.1
-0.2
-0.3
-0.1
-0.2
-0.3
0
32 64 96 128 160 192 224 256
CODE
0
32 64 96 128 160 192 224 256
CODE
0
32 64 96 128 160 192 224 256
CODE
_______________________________________________________________________________________
5
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
Typical Operating Characteristics (continued)
(V
= +5V, H_ = V , L_ = GND, T = +25°C, unless otherwise noted.)
DD A
DD
DIFFERENTIAL NONLINEARITY
vs. CODE (VRM MODE)
INTEGRAL NONLINEARITY
vs. CODE (VDM MODE)
DIFFERENTIAL NONLINEARITY
vs. CODE (VDM MODE)
0.20
0.16
0.12
0.08
0.04
0
0.10
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
MAX5479
MAX5479
MAX5478
0.08
0.06
0.04
0.02
0
-0.02
-0.04
-0.08
-0.12
-0.16
-0.20
-0.02
-0.04
-0.06
-0.08
-0.10
-0.12
-0.14
-0.04
-0.06
-0.08
-0.10
0
32 64 96 128 160 192 224 256
CODE
0
32 64 96 128 160 192 224 256
CODE
0
32 64 96 128 160 192 224 256
CODE
INTEGRAL NONLINEARITY
vs. CODE (VRM MODE)
DIFFERENTIAL NONLINEARITY
vs. CODE (VRM MODE)
0.20
0.16
0.12
0.08
0.04
0
0.20
0.16
0.12
0.08
0.04
0
MAX5479
MAX5479
-0.04
-0.08
-0.12
-0.16
-0.20
-0.04
-0.08
-0.12
-0.16
-0.20
0
0
32 64 96 128 160 192 224 256
CODE
32 64 96 128 160 192 224 256
CODE
CROSSTALK vs. FREQUENCY (MAX5479)
CROSSTALK vs. FREQUENCY (MAX5478)
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
0
-10
-20
-30
-40
-50
-60
-70
-80
-90
-100
C
= 10pF
W_
C
= 10pF
W_
TAP = 0
TAP = 128
0.1
1
10
100
1000 10,000
0.01
0.1
1
10
100
1000
FREQUENCY (kHz)
FREQUENCY (kHz)
6
_______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
Typical Operating Characteristics (continued)
(V
= +5V, H_ = V , L_ = GND, T = +25°C, unless otherwise noted.)
DD
DD
A
MIDSCALE WIPER RESPONSE
vs. FREQUENCY (MAX5478)
MIDSCALE WIPER RESPONSE
vs. FREQUENCY (MAX5479)
2
1
2
1
C
= 10pF
W_
0
0
-1
-2
-3
-4
-5
-6
-7
-8
-1
-2
-3
-4
-5
C
= 10pF
W_
C
= 50pF
W_
C
= 50pF
10
W_
0.1
1
10
FREQUENCY (kHz)
100
1000
0.1
1
100
1000
FREQUENCY (kHz)
THD+N vs. FREQUENCY
(MAX5479)
THD+N vs. FREQUENCY
(MAX5478)
10
1
10
1
MIDSCALE
MIDSCALE
0.1
0.1
0.01
0.001
0.0001
0.01
0.001
0.0001
0.01
0.1
1
10
100
0.01
0.1
1
10
100
FREQUENCY (kHz)
FREQUENCY (kHz)
SUPPLY CURRENT
vs. DIGITAL INPUT VOLTAGE
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE (MAX5478)
END-TO-END RESISTANCE % CHANGE
vs. TEMPERATURE (MAX5479)
0.5
0.5
600
WP = GND
550
500
0.4
0.3
0.4
0.3
450
400
350
300
0.2
0.2
0.1
0.1
V
= 5V
CC
0
0
250
200
-0.1
-0.2
-0.3
-0.4
-0.5
-0.1
-0.2
-0.3
-0.4
-0.5
V
= 3V
CC
150
100
50
0
0
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
DIGITAL INPUT VOLTAGE (V)
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
7
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
Pin Description
PIN
THIN QFN
NAME
FUNCTION
TSSOP
1
2
3
4
5
6
15
14
13
12
11
10
HA
WA
LA
Potentiometer A High Terminal
Potentiometer A Wiper Terminal
Potentiometer A Low Terminal
Potentiometer B High Terminal
Potentiometer B Wiper Terminal
Potentiometer B Low Terminal
HB
WB
LB
Write-Protect Input. Connect to GND to allow changes to the wiper position and the data stored
in the EEPROM. Connect to V or leave open to enable the write protection of the EEPROM.
7
9
WP
DD
8
7
6
5
4
3
2
GND Ground
9
A2
A1
Address Input 2. Connect to V
or GND (see Table 1).
or GND (see Table 1).
or GND (see Table 1).
DD
DD
DD
10
11
12
13
Address Input 1. Connect to V
Address Input 0. Connect to V
I2C Serial Data
A0
SDA
SCL
I2C Clock Input
Power-Supply Input. Connect a +2.7V to +5.25V power supply to V
with a 0.1µF capacitor installed as close to the device as possible.
and bypass V
to GND
DD
DD
14
1
V
DD
—
—
8, 16
EP
N.C.
EP
No Connection. Do not connect.
Exposed Paddle. Do not connect.
SDA
SCL
t
BUF
t
SU:DAT
t
SU:STA
t
t
SU:STO
HD:DAT
t
LOW
t
HD:STA
t
HIGH
t
HD:STA
t
R
t
F
STOP
CONDITION
(P)
START
CONDITION
(S)
START
CONDITION
(S)
REPEATED START
CONDITION
(SR)
ACKNOWLEDGE
(A)
PARAMETERS ARE MEASURED FROM 30% TO 70%.
2
Figure 1. I C Serial-Interface Timing Diagram
The MAX5477/MAX5478/MAX5479 provide access to
the high, low, and wiper terminals for a standard volt-
age-divider configuration. Connect H_, L_, and W_ in
any desired configuration as long as their voltages
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.
remain between GND and V
.
DD
8
_______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
A simple 2-wire I2C-compatible serial interface moves
the wiper among the 256 tap points (Figure 2). A non-
H_
volatile memory stores the wiper position and recalls
the stored wiper position upon power-up. The non-
volatile memory is guaranteed for 50 years for wiper
data retention and up to 200,000 wiper store cycles.
S
S
S
256
255
254
R
R
255
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 inter-
face. 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.
254
R
W
256-POSITION
DECODER
W_
S
3
S
2
S
1
WIPER
CODE 02h
R
R
2
1
Digital Interface
The MAX5477/MAX5478/MAX5479 feature an internal,
nonvolatile EEPROM that stores the wiper state for ini-
tialization 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 posi-
tion, or writes data to a nonvolatile register for storage
(see Table 2).
L_
Figure 2. Potentiometer Configuration
The volatile register retains data as long as the device
is powered. Removing power clears the volatile regis-
ter. 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 non-
volatile register to the volatile register.
SDA
S
P
SCL
START
CONDITION
STOP
CONDITION
A write-protect feature prevents accidental overwriting
of the EEPROM. Connect WP to V
or leave open to
DD
prevent any EEPROM write cycles. The wiper register
only updates with the value in the EEPROM when WP =
Figure 3. Start and Stop Conditions
SDA
0
1
0
1
A2
A1
A0
NOP/W
ACK
START
MSB
LSB
SCL
Figure 4. Slave Address
_______________________________________________________________________________________
9
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
interface, or if the master in a single-master system has
an open-drain SCL output. SCL and SDA should not
Table 1. Slave Addresses
AꢂꢂRESS INPUTS
exceed V
in a mixed-voltage system, despite the
DD
SꢀAVE AꢂꢂRESS
open-drain drivers.
A2
A1
A0
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).
GND
GND
GND
GND
GND
GND
GND
0101000
0101001
0101010
0101011
0101100
0101101
0101110
0101111
V
DD
V
V
GND
DD
DD
V
DD
V
V
V
V
GND
GND
GND
DD
DD
DD
DD
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).
V
DD
V
V
GND
DD
DD
V
DD
V
. Connect WP to GND to allow write commands to
DD
the EEPROM and to update the wiper position from
either the value in the EEPROM or directly from the I2C
interface. Connecting WP to GND increases the supply
current by 19.6µA (max).
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).
Serial Addressing
The MAX5477/MAX5478/MAX5479 operate as slave
devices that send and receive data through an I2C-/
SMBus™-compatible 2-wire serial interface. The inter-
face 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).
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.
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 (typ-
ically 4.7kΩ) if there are multiple masters on the 2-wire
Slave Address
The MAX5477/MAX5478/MAX5479 have a 7-bit-long
slave address (Figure 4). The 8th bit following the 7-bit
CLOCK PULSE FOR
ACKNOWLEDGMENT
START
SDA
CONDITION
SCL
1
2
8
9
NOT ACKNOWLEDGE
SCL
SDA
DATA STABLE, CHANGE OF
DATA VALID
DATA ALLOWED
ACKNOWLEDGE
Figure 5. Bit Transfer
Figure 6. Acknowledge
SMBus is a trademark of Intel Corporation.
10 ______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
COMMAND BYTE IS STORED ON RECEIPT OF STOP CONDITION
D15
D14
D13
D12
D11
D10
D9
D8
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
S
SLAVE ADDRESS
0
A
COMMAND BYTE
A
P
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
NOP/W
Figure 7. Command Byte Received
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
HOW CONTROL BYTE AND DATA BYTE MAP INTO
MAX5477/MAX5478/MAX5479 REGISTERS
D15 D14 D13 D12 D11 D10 D9 D8
D7 D6 D5 D4 D3 D2 D1 D0
ACKNOWLEDGE FROM
MAX5477/MAX5478/MAX5479
A
P
S
SLAVE ADDRESS
0
A
COMMAND BYTE
A
DATA BYTE
1 BYTE
NOP/W
Figure 8. Command and Single Data Byte Received
NVREG: The data byte writes to the nonvolatile memory
register. The wiper position is unchanged.
slave address is the NOP/W bit. Set the NOP/W bit low for
a write command and high for a no-operation command.
NVREGxVREG: Data transfers from the nonvolatile
memory register to the volatile memory register (wiper
position updates).
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
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.
to V
or GND to set these 3 bits. Each device must
DD
have a unique address to share a common bus.
Message Format for Writing
Write to the MAX5477/MAX5478/MAX5479 by transmit-
ting 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 select-
ed by the command byte (Figure 8).
Connect WP to V
or leave open to enable the write-
DD
protect feature. The wiper position only updates with
the value in the EEPROM when WP = V . Connect WP
DD
to GND to allow EEPROM write cycles and to update
the wiper position from nonvolatile memory or directly
from the I2C serial interface.
Command Byte
Use the command byte to select the source and desti-
nation of the wiper data (nonvolatile or volatile memory
registers) and swap data between nonvolatile and
volatile memory registers (see Table 2).
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.
Command Descriptions
VREG: The data byte writes to the volatile memory reg-
ister and the wiper position updates with the data in the
volatile memory register.
______________________________________________________________________________________ 11
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
Table 2. Command ꢁyte Summary
AꢂꢂRESS ꢁYTE
COMMANꢂ ꢁYTE
ꢂATA ꢁYTE
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27
NOTES
SCL CYCLE START
STOP
(P)
ACK
(A)
ACK
(A)
ACK
(A)
NUMBER
(S)
A6 A5 A4 A3 A2 A1 A0
TX NV V R3 R2 R1 R0
D7 D6 D5 D4 D3 D2 D1 D0
VREG
NVREG
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
A2 A1 A0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
0
0
1
1
0
0
1
1
0
1
1
0
0
1
1
0
0
1
1
0
1
0
0
1
1
0
0
1
1
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
1
1
1
1
0
0
0
0
1
1
1
1
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
D7 D6 D5 D4 D3 D2 D1 D0
WIPER A
ONLY
NVREGxVREG
VREGxNVREG
VREG
NVREG
WIPER B
ONLY
NVREGxVREG
VREGxNVREG
VREG
NVREG
WIPERS
A AND B
NVREGxVREG
VREGxNVREG
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).
Standby
The MAX5477/MAX5478/MAX5479 feature a low-power
standby mode. When the device is not being pro-
grammed, it enters into standby mode and supply cur-
rent drops to 500nA (typ).
Programmable Filter
Figure 11 shows the MAX5477/MAX5478/MAX5479 in a
1st-order programmable application filter. Adjust the
Applications Information
gain of the filter with R , and set the cutoff frequency
2
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 fil-
ters with adjustable gain and/or cutoff frequency.
with R . Use the following equations to calculate the
3
gain (A) and the -3dB cutoff frequency (f ):
C
R
1
A = 1 +
R
2
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-
1
f
=
C
2π × R × C
3
5V
5V
H_
30V
30V
W_
MAX5477
MAX5478
MAX5479
V
OUT
H_
V
OUT
MAX480
MAX480
L_
MAX5477
MAX5478
MAX5479
W_
L_
Figure 10. Positive LCD Bias Control Using a Variable Resistor
12 ______________________________________________________________________________________
Figure 9. Positive LCD Bias Control Using a Voltage-Divider
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
5V
WA
V+
1/2 MAX5477
WA
LA
V
IN
HA
R
3
HA
LA
C
V
OUT
MAX410
7
3
2
1
8
MAX5477
MAX5478
MAX5479
V-
6
MAX410
R
1
4
R = R x D / 256
WHERE R = END-TO-END RESISTANCE
AND = D DECIMAL VALUE OF WIPER CODE
2
HL
HB
R , R = R x D / 256
2
3
HL
R1
HL
WHERE R = END-TO-END RESISTANCE
AND D = DECIMAL VALUE OF WIPER CODE
HL
HB
WB
R
2
1/2 MAX5477
R2
WB
LB
LB
Figure 11. Programmable Filter
Figure 12. Offset Voltage Adjustment Circuit
5V
10kΩ
V
V
V
= 1.23V x
= 1.23V x
= 1.23V x
FOR THE MAX5477
FOR THE MAX5478
FOR THE MAX5479
IN
IN
OUT_
OUT_
OUT_
R
V
OUT
ADJ
OUT
V
OUT1
OUT2
50kΩ
R
HB
LB
HA
MAX6160
MAX6160
100kΩ
R
WA
WB
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
1/2 MAX5477
1/2 MAX5478
1/2 MAX5479
ADJ
WHERE R = R x D / 256
HL
AND D = DECIMAL VALUE OF WIPER CODE
R
R
GND
GND
LA
Figure 13. Adjustable Voltage Reference
Offset Voltage and Gain Adjustment
Connect the high and low terminals of one potentiome-
ter 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 tempera-
ture range. Install the other potentiometer in the feed-
back path to adjust the gain of the MAX410 (Figure 12).
Pin Configurations
TOP VIEW
N.C. HA
WA
14
LA
13
16
15
HA
WA
LA
1
2
3
4
5
6
7
14 V
DD
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
DD
HB
WB
LB
1
2
3
4
12
11
10
9
13 SCL
12 SDA
11 A0
SCL
SDA
A0
MAX5477
MAX5478
MAX5479
MAX5477
MAX5478
MAX5479
HB
WB
LB
10 A1
WP
V
- 0.2V by changing the wiper positions of the
9
8
A2
IN
MAX5477/MAX5478/MAX5479.
5
6
7
8
WP
GND
A1
A2 GND
N.C.
Chip Information
TRANSISTOR COUNT: 12,651
THIN QFN
TSSOP
(4.4mm x 5mm)
(3mm x 3mm)
PROCESS: BiCMOS
______________________________________________________________________________________ 13
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
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.)
D2
b
0.10 M
C
A
B
D
D2/2
D/2
E/2
E2/2
(NE - 1)
X e
C
E
E2
L
L
k
e
C
L
(ND - 1)
X e
C
L
C
L
0.10
C
0.08 C
A
A2
A1
L
L
e
e
PACKAGE OUTLINE
12, 16L, THIN QFN, 3x3x0.8mm
1
E
21-0136
2
EXPOSED PAD VARIATIONS
DOWN
BONDS
ALLOWED
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
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.
PACKAGE OUTLINE
12, 16L, THIN QFN, 3x3x0.8mm
2
E
21-0136
2
14 ______________________________________________________________________________________
Dual, 256-Tap, Nonvolatile, I2C-Interface,
Digital Potentiometers
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.)
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.
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