DATASHEET
NOT RECOMMENDED FOR NEW DESIGNS
RECOMMENDED REPLACEMENT PART
ISL23425
ISL23348
FN7903
Rev 1.00
August 24, 2011
Quad, 128 Tap, Low Voltage Digitally Controlled Potentiometer (XDCP™)
The ISL23348 is a volatile, low voltage, low noise, low power,
128 tap, quad digitally controlled potentiometer (DCP) with an
I2C Bus™ interface. It integrates four DCP cores, wiper
switches and control logic on a monolithic CMOS integrated
circuit.
Features
Each digitally controlled potentiometer is implemented with a
combination of resistor elements and CMOS switches. The
position of the wipers are controlled by the user through the
I2C bus interface. Each potentiometer has an associated
volatile Wiper Register (WRi, i = 0, 1, 2, 3) that can be directly
written to and read by the user. The contents of the WRi
controls the position of the wiper. When powered on, the wiper
of each DCP will always commence at mid-scale (64 tap
position).
• I2C serial interface
- No additional level translator for low bus supply
- Three address pins allow up to eight devices per bus
The low voltage, low power consumption, and small package
of the ISL23348 make it an ideal choice for use in battery
operated equipment. In addition, the ISL23348 has a VLOGIC
pin allowing down to 1.2V bus operation, independent from the
VCC value. This allows for low logic levels to be connected
directly to the ISL23348 without passing through a voltage
level shifter.
The DCP can be used as a three-terminal potentiometer or as a
two-terminal variable resistor in a wide variety of applications
including control, parameter adjustments, and signal processing.
• Four potentiometers per package
• 128 resistor taps
• 10kΩ 50kΩor 100kΩ total resistance
• Maximum supply current without serial bus activity
(standby)
- 5µA @ VCC and VLOGIC = 5V
- 2µA @ VCC and VLOGIC = 1.7V
• Shutdown mode
- Forces the DCP into an end-to-end open circuit and RWi is
connected to RLi internally
- Reduces power consumption by disconnecting the DCP
resistor from the circuit
• Power supply
- VCC = 1.7V to 5.5V analog power supply
- VLOGIC = 1.2V to 5.5V I2C bus/logic power supply
• Wiper resistance: 70Ω typical @ VCC = 3.3V
• Power-on preset to mid-scale (64 tap position)
Applications
• Extended industrial temperature range: -40°C to +125°C
• Power supply margining
• 20 Ld TSSOP or 20 QFN packages
• Trimming sensor circuits
• Pb-free (RoHS compliant)
• Gain adjustment in battery powered instruments
• RF power amplifier bias compensation
10000
VREF
RESISTANCE (Ω)
8000
RH1
6000
1 DCP
OF
ISL23348
4000
RW1
VREF_M
+
ISL28114
2000
RL1
0
0
32
64
TAP POSITION (DECIMAL)
96
FIGURE 1. FORWARD AND BACKWARD RESISTANCE vs TAP
POSITION, 10kΩ DCP
FN7903 Rev 1.00
August 24, 2011
128
FIGURE 2. VREF ADJUSTMENT
Page 1 of 19
ISL23348
Block Diagram
VLOGIC
VCC
RH0
SCL
SDA
LEVEL
SHIFTER
I/O
BLOCK
A0
A1
A2
POWER UP
INTERFACE
CONTROL
AND
STATUS
LOGIC
WR0
VOLATILE
REGISTER
RW0
WR1
VOLATILE
REGISTER
RW1
WR2
VOLATILE
REGISTER
RW2
WR3
VOLATILE
REGISTER
RW3
RL0
RH1
RL1
RH2
RL2
RH3
RL3
GND
Pin Configurations
Pin Descriptions
ISL23348
(20 LD TSSOP)
TOP VIEW
RL0
1
20 RL3
RW0
2
19 RW3
TSSOP
QFN
SYMBOL
DESCRIPTION
1
19
RL0
DCP0 “low” terminal
2
20
RW0
DCP0 wiper terminal
3
1
VCC
Analog power supply.
Range 1.7V to 5.5V
VCC
3
18 RH3
RH0
4
17 RL2
4
2
RH0
DCP0 “high” terminal
RL1
5
16 RW2
5
3
RL1
DCP1 “low” terminal
RW1
6
15 RH2
6
4
RW1
DCP1 wiper terminal
RH1
7
14 SCL
GND
8
13 SDA
7
5
RH1
DCP1 “high” terminal
VLOGIC
9
12 A2
8
6
GND
Ground pin
A0 10
11 A1
9
7
VLOGIC
I2C bus /logic supply. Range 1.2V to 5.5V
10
8
A0
Logic Pin - Hardwire slave address pin for
I2C serial bus.
Range: VLOGIC or GND
11
9
A1
Logic Pin - Hardwire slave address pin for
I2C serial bus.
Range: VLOGIC or GND
12
10
A2
Logic Pin - Hardwire slave address pin for
I2C serial bus.
Range: VLOGIC or GND
13
11
SDA
Logic Pin - Serial bus data input/open
drain output
14
12
SCL
Logic Pin - Serial bus clock input
RL0
RL3
RW3
20
19
18
17
VCC
1
6
16
RH3
RH0
2
15
RL2
RL1
3
14
RW2
RW1
4
13
RH2
15
13
RH2
DCP2 “high” terminal
RH1
5
12
SCL
16
14
RW2
DCP2 wiper terminal
GND
6
11
SDA
17
15
RL2
DCP2 “low” terminal
10
18
16
RH3
DCP3 “high” terminal
A2
RW0
ISL23348
(20 LD QFN)
TOP VIEW
19
17
RW3
DCP3 wiper terminal
20
18
RL3
DCP3 “low” terminal
FN7903 Rev 1.00
August 24, 2011
9
A1
8
A0
VLOGIC
7
Page 2 of 19
ISL23348
Ordering Information
PART NUMBER
(Notes 1, 2, 3)
PART MARKING
RESISTANCE
OPTION
(kΩ)
TEMP RANGE
(°C)
-40 to +125
PACKAGE
(Pb-free)
20 Ld TSSOP
PKG.
DWG. #
ISL23348TFVZ
23348 TFVZ
100
M20.173
ISL23348UFVZ
23348 UFVZ
50
-40 to +125
20 Ld TSSOP
M20.173
ISL23348WFVZ
23348 WFVZ
10
-40 to +125
20 Ld TSSOP
M20.173
ISL23348TFRZ
348T
100
-40 to +125
20 Ld 3x4 QFN
L20.3x4
ISL23348UFRZ
348U
50
-40 to +125
20 Ld 3x4 QFN
L20.3x4
ISL23348WFRZ
348W
10
-40 to +125
20 Ld 3x4 QFN
L20.3x4
NOTES:
1. Add “-TK” suffix for 1k unit or “-T7A” suffix for 250 unit Tape and Reel options. Please refer to TB347 for details on reel specifications.
2. These Intersil Pb-free plastic packaged products employ special Pb-free material sets, molding compounds/die attach materials, and 100% matte tin
plate plus anneal (e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations). Intersil Pb-free
products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020.
3. For Moisture Sensitivity Level (MSL), please see device information page for ISL23348. For more information on MSL please see techbrief TB363.
FN7903 Rev 1.00
August 24, 2011
Page 3 of 19
ISL23348
Absolute Maximum Ratings
Thermal Information
Supply Voltage Range
VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
VLOGIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
Voltage on Any DCP Terminal Pin . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
Voltage on Any Digital Pins . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3V to 6.0V
Wiper Current IW (10s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±6mA
ESD Rating
Human Body Model (Tested per JESD22-A114E) . . . . . . . . . . . . . . . . 6kV
CDM Model (Tested per JESD22-A114E) . . . . . . . . . . . . . . . . . . . . . . . 1kV
Machine Model (Tested per JESD22-A115-A) . . . . . . . . . . . . . . . . . 300V
Latch Up (Tested per JESD-78B; Class 2, Level A) . . . . 100mA @ +125°C
Thermal Resistance (Typical)
JA (°C/W) JC (°C/W)
20 Ld TSSOP Package (Notes 4, 6) . . . . . .
85
33
20 Ld QFN Package (Notes 5, 7) . . . . . . . .
40
4
Maximum Junction Temperature (Plastic Package) . . . . . . . . . . . .+150°C
Storage Temperature Range. . . . . . . . . . . . . . . . . . . . . . . .-65°C to +150°C
Pb-Free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . see link below
http://www.intersil.com/pbfree/Pb-FreeReflow.asp
Recommended Operating Conditions
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +125°C
VCC Supply Voltage. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.7V to 5.5V
VLOGIC Supply Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1.2V to 5.5V
DCP Terminal Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .0 to VCC
Max Wiper Current . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ±3mA
CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product
reliability and result in failures not covered by warranty.
NOTES:
4. JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
5. JA is measured in free air with the component mounted on a high effective thermal conductivity test board with “direct attach” features. See Tech
Brief TB379.
6. For JC, the “case temp” location is taken at the package top center.
7. For JC, the “case temp” location is the center of the exposed metal pad on the package underside.
Analog Specifications VCC = 2.7V to 5.5V, VLOGIC = 1.2V to 5.5V over recommended operating conditions unless otherwise stated.
Boldface limits apply over the operating temperature range, -40°C to +125°C.
SYMBOL
RTOTAL
PARAMETER
RH to RL Resistance
TEST CONDITIONS
VRH, VRL
U option
50
kΩ
T option
100
kΩ
-20
±2
+20
%
W option
125
ppm/°C
U option
65
ppm/°C
T option
45
ppm/°C
Wiper Resistance
RH - floating, VRL = 0V, force IW current to the
wiper, IW = (VCC - VRL)/RTOTAL, VCC = 2.7V to 5.5V
CH/CL/CW
Terminal Capacitance
See “DCP Macro Model” on page 9
ILkgDCP
Leakage on DCP Pins
Voltage at pin from GND to VCC
Noise
Resistor Noise Density
0
70
VCC = 1.7V
PSRR
UNITS
kΩ
VRH or VRL to GND
Feed Thru
MAX
(Note 20)
10
DCP Terminal Voltage
RW
TYP
(Note 8)
W option
RH to RL Resistance Tolerance
End-to-End Temperature Coefficient
MIN
(Note 20)
-0.4
VCC
V
200
Ω
580
Ω
32/32/32
pF
2V
0
IOL = 1.5mA, VLOGIC < 2V
Cpin
SDA, SCL Pin Capacitance
fSCL
SCL Frequency
tsp
Pulse Width Suppression Time at
SDA and SCL Inputs
tAA
0.4
V
0.2 x VLOGIC
V
10
pF
400
kHz
Any pulse narrower than the max spec is
suppressed
50
ns
SCL Falling Edge to SDA Output
Data Valid
SCL falling edge crossing 30% of VLOGIC, until
SDA exits the 30% to 70% of VLOGIC window
900
ns
tBUF
Time the Bus Must be Free Before
the Start of a New Transmission
SDA crossing 70% of VLOGIC during a STOP
condition, to SDA crossing 70% of VLOGIC during
the following START condition
1300
ns
tLOW
Clock LOW Time
Measured at the 30% of VLOGIC crossing
1300
ns
tHIGH
Clock HIGH Time
Measured at the 70% of VLOGIC crossing
600
ns
tSU:STA
START Condition Set-up Time
SCL rising edge to SDA falling edge; both crossing
70% of VLOGIC
600
ns
tHD:STA
START Condition Hold Time
From SDA falling edge crossing 30% of VLOGIC to
SCL falling edge crossing 70% of VLOGIC
600
ns
tSU:DAT
Input Data Set-up Time
From SDA exiting the 30% to 70% of VLOGIC
window, to SCL rising edge crossing 30% of
VLOGIC
100
ns
tHD:DAT
Input Data Hold Time
From SCL falling edge crossing 70% of VLOGIC to
SDA entering the 30% to 70% of VLOGIC window
0
ns
FN7903 Rev 1.00
August 24, 2011
Page 7 of 19
ISL23348
Serial Interface Specification
SYMBOL
For SCL, SDA, A0, A1, A2 unless otherwise noted. (Continued)
PARAMETER
TEST CONDITIONS
tSU:STO
STOP Condition Set-up Time
From SCL rising edge crossing 70% of VLOGIC, to
SDA rising edge crossing 30% of VLOGIC
tHD:STO
STOP Condition Hold Time for Read From SDA rising edge to SCL falling edge; both
or Write
crossing 70% of VLOGIC
MIN
(Note 20)
TYP
(Note 8)
MAX
(Note 20)
UNITS
600
ns
1300
ns
0
ns
tDH
Output Data Hold Time
From SCL falling edge crossing 30% of VLOGIC,
until SDA enters the 30% to 70% of VLOGIC
window. IOL = 3mA, VLOGIC > 2V. IOL = 0.5mA,
VLOGIC < 2V
tR
SDA and SCL Rise Time
From 30% to 70% of VLOGIC
20 + 0.1 x Cb
250
ns
tF
SDA and SCL Fall Time
From 70% to 30% of VLOGIC
20 + 0.1 x Cb
250
ns
Cb
Capacitive Loading of SDA or SCL
Total on-chip and off-chip
10
400
pF
tSU:A
A1, A0, A2 Setup Time
Before START condition
600
ns
tHD:A
A1, A0, A2 Hold Time
After STOP condition
600
ns
NOTES:
8. Typical values are for TA = +25°C and 3.3V supply voltages.
9. LSB = [V(RW)127 – V(RW)0]/127. V(RW)127 and V(RW)0 are V(RW) for the DCP register set to 7f hex and 00 hex respectively. LSB is the incremental
voltage when changing from one tap to an adjacent tap.
10. ZS error = V(RW)0/LSB.
11. FS error = [V(RW)127 – VCC]/LSB.
12. DNL = [V(RW)i – V(RW)i-1]/LSB-1, for i = 1 to 127. i is the DCP register setting.
13. INL = [V(RW)i – i • LSB – V(RW)0]/LSB for i = 1 to 127
Max V RW i – Min V RW i
14.
for i = 16 to 127 decimal, T = -40°C to +125°C. Max( ) is the maximum value of the wiper voltage
10 6
TC V = ------------------------------------------------------------------------------ --------------------V RW i +25°C
+165°C and Min( ) is the minimum value of the wiper voltage over the temperature range.
15. MI = |RW127 – RW0|/127. MI is a minimum increment. RW127 and RW0 are the measured resistances for the DCP register set to 7f hex and 00
hex respectively.
16. Roffset = RW0/MI, when measuring between RW and RL.
Roffset = RW127/MI, when measuring between RW and RH.
17. RDNL = (RWi – RWi-1)/MI -1, for i = 8 to 127.
18. RINL = [RWi – (MI • i) – RW0]/MI, for i = 8 to 127.
6
for i = 8 to 127, T = -40°C to +125°C. Max( ) is the maximum value of the resistance and Min( ) is the
Max Ri – Min Ri
10
TC R = ------------------------------------------------------- --------------------Ri +25°C
+165°C minimum value of the resistance over the temperature range.
20. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design.
19.
21. It is preferable to ramp up both the VLOGIC and the VCC supplies at the same time. If this is not possible, it is recommended to ramp-up the VLOGIC
first followed by the VCC.
22. VMATCH = [V(RWx)i - V(RWy)i]/LSB, for i = 1 to 127, x = 0 to 3 and y = 0 to 3.
23. RMATCH = (RWi,x - RWi,y)/MI, for i = 1 to 127, x = 0 to 3 and y = 0 to 3.
FN7903 Rev 1.00
August 24, 2011
Page 8 of 19
ISL23348
DCP Macro Model
RTOTAL
RH
RL
CH
CL
CW
32pF
32pF
32pF
RW
Timing Diagrams
SDA vs SCL Timing
tHIGH
tF
SCL
tLOW
tsp
tR
tSU:DAT
tSU:STA
SDA
(INPUT TIMING)
tHD:DAT
tHD:STA
tSU:STO
tAA
tDH
tBUF
SDA
(OUTPUT TIMING)
A0, A1 and A2 Pin Timing
START
SCL
STOP
CLK 1
SDA
tSU:A
tHD:A
A0, A1, A2
FN7903 Rev 1.00
August 24, 2011
Page 9 of 19
ISL23348
Typical Performance Curves
0.15
0.04
0.02
0.05
DNL (LSB)
DNL (LSB)
0.10
0.00
-0.05
0.00
-0.02
-0.10
-0.15
0
32
64
96
128
-0.04
0
32
64
TAP POSITION (DECIMAL)
96
128
TAP POSITION (DECIMAL)
FIGURE 3. 10kΩ DNL vs TAP POSITION, VCC = 3.3V, +25°C
FIGURE 4. 50kΩ DNL vs TAP POSITION, VCC = 3.3V, +25°C
0.15
0.16
0.10
0.12
INL (LSB)
INL (LSB)
0.05
0.00
-0.05
0.08
0.04
-0.10
0.00
-0.15
0
32
64
96
128
TAP POSITION (DECIMAL)
0
32
64
96
128
TAP POSITION (DECIMAL)
FIGURE 5. 10kΩ INL vs TAP POSITION, VCC = 3.3V, +25°C
FIGURE 6. 50kΩ INL vs TAP POSITION, VCC = 3.3V, +25°C
0.15
0.04
0.10
0.02
RDNL (MI)
RDNL (MI)
0.05
0.00
-0.05
0.00
-0.02
-0.10
-0.04
-0.15
0
32
64
96
TAP POSITION (DECIMAL)
FIGURE 7. 10kΩ RDNL vs TAP POSITION, VCC = 3.3V, +25°C
FN7903 Rev 1.00
August 24, 2011
0
128
32
64
96
128
TAP POSITION (DECIMAL)
FIGURE 8. 50kΩ RDNL vs TAP POSITION, VCC = 3.3V, +25°C
Page 10 of 19
ISL23348
Typical Performance Curves
(Continued)
0.08
0.30
0.25
0.04
RINL (MI)
RINL (MI)
0.20
0.15
0.00
0.10
-0.04
0.05
0.00
-0.08
0
32
64
96
128
TAP POSITION (DECIMAL)
0
96
128
FIGURE 10. 50kΩ RINL vs TAP POSITION, VCC = 3.3V, +25°C
100
120
+25°C
+125°C
80
WIPER RESISTANCE (Ω)
WIPER RESISTANCE (Ω)
64
TAP POSITION (DECIMAL)
FIGURE 9. 10kΩ RINL vs TAP POSITION, VCC = 3.3V, +25°C
60
40
-40°C
20
0
0
32
64
96
128
TAP POSITION (DECIMAL)
+25°C
100
+125°C
80
60
40
-40°C
20
0
0
FIGURE 11. 10kΩ WIPER RESISTANCE vs TAP POSITION, VCC = 3.3V
200
40
150
30
100
50
32
64
96
TAP POSITION (DECIMAL)
128
FIGURE 12. 50kΩ WIPER RESISTANCE vs TAP POSITION, VCC = 3.3V
TCv (ppm/°C)
TCv (ppm/°C)
32
20
10
0
0
15
43
71
99
TAP POSITION (DECIMAL)
FIGURE 13. 10kΩ TCv vs TAP POSITION, VCC = 3.3V
FN7903 Rev 1.00
August 24, 2011
127
15
43
71
99
127
TAP POSITION (DECIMAL)
FIGURE 14. 50kΩ TCv vs TAP POSITION, VCC = 3.3V
Page 11 of 19
ISL23348
Typical Performance Curves
(Continued)
100
400
80
TCr (ppm/°C)
TCr (ppm/°C)
300
200
100
60
40
20
0
0
15
43
71
99
TAP POSITION (DECIMAL)
127
15
43
71
99
127
TAP POSITION (DECIMAL)
FIGURE 15. 10kΩ TCr vs TAP POSITION
FIGURE 16. 50kΩ TCr vs TAP POSITION, VCC = 3.3V
100
20
80
TCr (ppm/°C)
TCv (ppm/°C)
15
10
5
60
40
20
0
0
15
43
71
99
TAP POSITION (DECIMAL)
FIGURE 17. 100kΩ TCv vs TAP POSITION, VCC = 3.3V
127
15
43
71
99
127
TAP POSITION (DECIMAL)
FIGURE 18. 100kΩ TCr vs TAP POSITION, VCC = 3.3V
CH1: 20mV/DIV, 2µs/DIV
CH2: 2V/DIV, 2µs/DIV
SCL CLOCK
RW PIN
WIPER
SCL
9TH CLK OF THE
DATA BYTE (ACK)
CH1: 1V/DIV, 1µs/DIV
CH2: 10mV/DIV, 1µs/DIV
FIGURE 19. WIPER DIGITAL FEED-THROUGH
FN7903 Rev 1.00
August 24, 2011
FIGURE 20. WIPER TRANSITION GLITCH
Page 12 of 19
ISL23348
Typical Performance Curves
1V/DIV
0.2µs/DIV
(Continued)
SCL
VCC
0.5V/DIV
20µs/DIV
SCL 9TH CLOCK OF THE
DATA BYTE (ACK)
WIPER
WIPER
CH1: RH TERMINAL
CH2: RW TERMINAL
0.5V/DIV, 0.2µs/DIV
-3dB FREQUENCY = 1.437MHz AT MIDDLE TAP
FIGURE 23. 10kΩ -3dB CUT OFF FREQUENCY
FIGURE 22. POWER-ON START-UP IN VOLTAGE DIVIDER MODE
1.8
STANDBY CURRENT ICC (µA)
FIGURE 21. WIPER LARGE SIGNAL SETTLING TIME
1.6
1.4
1.2
1.0
VCC = 5.5V, VLOGIC = 5.5V
0.8
0.6
0.4
VCC = 1.7V, VLOGIC = 1.2V
0.2
0
-40
-15
10
35
60
Bus Interface Pins
Potentiometers Pins
SERIAL DATA INPUT/OUTPUT (SDA)
The high (RHi, i = 0, 1, 2, 3) and low (RLi, i = 0, 1, 2, 3) terminals
of the ISL23348 are equivalent to the fixed terminals of a
mechanical potentiometer. RHi and RLi are referenced to the
relative position of the wiper and not the voltage potential on the
terminals. With WRi set to 127 decimal, the wiper will be closest
to RHi, and with the WRi set to 0, the wiper is closest to RLi.
RWI
RWi (i = 0, 1, 3) is the wiper terminal, and it is equivalent to the
movable terminal of a mechanical potentiometer. The position of
the wiper within the array is determined by the WRi register.
VCC
Power terminal for the potentiometer section analog power source.
Can be any value needed to support the voltage range of the DCP
pins, from 1.7V to 5.5V, independent of the VLOGIC voltage.
FN7903 Rev 1.00
August 24, 2011
110
FIGURE 24. STANDBY CURRENT vs TEMPERATURE
Functional Pin Descriptions
RHI AND RLI
85
TEMPERATURE (°C)
The SDA is a bidirectional serial data input/output pin for I2C
interface. It receives device address, wiper address and data
from an I2C external master device at the rising edge of the serial
clock SCL, and it shifts out data after each falling edge of the
serial clock.
SDA requires an external pull-up resistor, since it is an open drain
input/output.
SERIAL CLOCK (SCL)
This input is the serial clock of the I2C serial interface. SCL
requires an external pull-up resistor, since a master is an open
drain output.
DEVICE ADDRESS (A2, A1, A0)
The address inputs are used to set the least significant 3 bits of
the 7-bit I2C interface slave address. A match in the slave
address serial data stream must match with the Address input
Page 13 of 19
ISL23348
pins in order to initiate communication with the ISL23348. A
maximum of eight ISL23348 devices may occupy the I2C serial
bus (see Table 3).
VLOGIC
Digital power source for the logic control section. It supplies an
internal level translator for 1.2V to 5.5V serial bus operation. Use
the same supply as the I2C logic source.
Memory Description
The ISL23348 contains five volatile 8-bit registers: Wiper Register
WR0, Wiper Register WR1, Wiper Register WR2, Wiper Register
WR3 and Access Control Register (ACR). The memory map of
ISL23348 is shown in Table 1. The Wiper Register WRi at address i
contains current wiper position of DCPi (i = 0, 1, 2, 3). The Access
Control Register (ACR) at address 10h contains information and
control bits described in Table 2.
Principles of Operation
The ISL23348 is an integrated circuit incorporating four DCPs
with its associated registers and an I2C serial interface providing
direct communication between a host and the potentiometer.
The resistor array is comprised of individual resistors connected
in series. At either end of the array and between each resistor is
an electronic switch that transfers the potential at that point to
the wiper.
The electronic switches on the device operate in a
“make-before-break” mode when the wiper changes tap
positions.
Voltage at any of the DCP pins, RHi, RLi or RWi, should not
exceed VCC level at any conditions during power-up and normal
operation.
The VLOGIC pin is the terminal for the logic control digital power
source. It should use the same supply as the I2C logic source,
which allows reliable communication with a wide range of
microcontrollers and is independent from the VCC level. This is
extremely important in systems where the master supply has
lower levels than the DCP analog supply.
DCP Description
Each DCP is implemented with a combination of resistor elements
and CMOS switches. The physical ends of each DCP are equivalent
to the fixed terminals of a mechanical potentiometer (RHi and RLi
pins). The RWi pin of the DCP is connected to intermediate nodes,
and is equivalent to the wiper terminal of a mechanical
potentiometer. The position of the wiper terminal within the DCP is
controlled by an 8-bit volatile Wiper Register (WRi). When the WRi of
a DCP contains all zeroes (WRi[7:0] = 00h), its wiper terminal (RW)
is closest to its “Low” terminal (RLi). When the WRi register of a DCP
contains all ones (WRi[7:0] = 7fh), its wiper terminal (RWi) is closest
to its “High” terminal (RHi). As the value of the WRi increases from
all zeroes (0) to all ones (127 decimal), the wiper moves
monotonically from the position closest to RLi to the position closest
to RHi. At the same time, the resistance between RWi and RLi
increases monotonically, while the resistance between RHi and RWi
decreases monotonically.
While the ISL23348 is being powered up, all the wipers (WRi) are
reset to 40h (64 decimal), which positions RWi at the center
between RLi and RHi.
The WRi can be read or written to directly using the I2C serial
interface as described in the following sections.
FN7903 Rev 1.00
August 24, 2011
TABLE 1. MEMORY MAP
ADDRESS
(hex)
VOLATILE
REGISTER NAME
DEFAULT SETTING
(hex)
10
ACR
40
3
WR3
40
2
WR2
40
1
WR1
40
0
WR0
40
TABLE 2. ACCESS CONTROL REGISTER (ACR)
BIT #
7
6
5
4
3
2
1
0
NAME/
VALUE
0
SHDN
0
0
0
0
0
0
Shutdown Function
The SHDN bit (ACR[6]) disables or enables shutdown mode for all
DCP channels simultaneously. When this bit is 0, i.e., DCP is forced
to end-to-end open circuit and RW is connected to RL through a
2kΩ serial resistor, as shown in Figure 25. The default value of the
SHDN bit is 1.
RH
RW
2kΩ
RL
FIGURE 25. DCP CONNECTION IN SHUTDOWN MODE
When the device enters shutdown, all current DCP WRi settings are
maintained. When the device exits shutdown, the wipers will return
to the previous WRi settings after a short settling time (see
Figure 26).
In shutdown mode, if there is a glitch on the power supply which
causes it to drop below 1.3V for more than 0.2µs to 0.4µs, the
wipers will be RESET to their mid positions. This is done to avoid
an undefined state at the wiper outputs.
Page 14 of 19
WIPER VOLTAGE, VRW (V)
ISL23348
POWER-UP
All I2C interface operations must begin with a START condition,
which is a HIGH-to-LOW transition of SDA while SCL is HIGH. The
ISL23348 continuously monitors the SDA and SCL lines for the
START condition and does not respond to any command until this
condition is met (see Figure 27). A START condition is ignored
during the power-up of the device.
MID SCALE = 80H
USER PROGRAMMED
AFTER SHDN
SHDN ACTIVATED SHDN RELEASED
WIPER RESTORE TO
THE ORIGINAL POSITION
SHDN MODE
0
TIME (s)
FIGURE 26. SHUTDOWN MODE WIPER RESPONSE
I2C Serial Interface
The ISL23348 supports an I2C bidirectional bus oriented
protocol. The protocol defines any device that sends data onto
the bus as a transmitter and the receiving device as the receiver.
The device controlling the transfer is a master and the device
being controlled is the slave. The master always initiates data
transfers and provides the clock for both transmit and receive
operations. Therefore, the ISL23348 operates as a slave device
in all applications.
All communication over the I2C interface is conducted by sending
the MSB of each byte of data first.
Protocol Conventions
Data states on the SDA line must change only during SCL LOW
periods. SDA state changes during SCL HIGH are reserved for
indicating START and STOP conditions (see Figure 27). On
power-up of the ISL23348, the SDA pin is in the input mode.
All I2C interface operations must be terminated by a STOP
condition, which is a LOW to HIGH transition of SDA while SCL is
HIGH (see Figure 27). A STOP condition at the end of a read
operation or at the end of a write operation places the device in
its standby mode.
An ACK (Acknowledge) is a software convention used to indicate
a successful data transfer. The transmitting device, either master
or slave, releases the SDA bus after transmitting eight bits.
During the ninth clock cycle, the receiver pulls the SDA line LOW
to acknowledge the reception of the eight bits of data
(see Figure 28).
The ISL23348 responds with an ACK after recognition of a START
condition followed by a valid Identification Byte, and once again
after successful receipt of an Address Byte. The ISL23348 also
responds with an ACK after receiving a Data Byte of a write
operation. The master must respond with an ACK after receiving
a Data Byte of a read operation.
A valid Identification Byte contains 1010 as the four MSBs, and
the following three bits are matching the logic values present at
pins A2, A1 and A0. The LSB is the Read/Write bit. Its value is “1”
for a Read operation and “0” for a Write operation (see Table 3).
TABLE 3. IDENTIFICATION BYTE FORMAT
LOGIC VALUES AT PINS A2, A1 AND A0 RESPECTIVELY
1
0
1
0
A2
(MSB)
A1
A0
R/W
(LSB)
SCL
SDA
START
DATA
STABLE
DATA
CHANGE
DATA
STABLE
STOP
FIGURE 27. VALID DATA CHANGES, START AND STOP CONDITIONS
FN7903 Rev 1.00
August 24, 2011
Page 15 of 19
ISL23348
SCL FROM
MASTER
1
8
9
SDA OUTPUT FROM
TRANSMITTER
HIGH IMPEDANCE
HIGH IMPEDANCE
SDA OUTPUT FROM
RECEIVER
START
ACK
FIGURE 28. ACKNOWLEDGE RESPONSE FROM RECEIVER
SIGNALS FROM
THE MASTER
S
T
A
R
T
SIGNAL AT SDA
WRITE
IDENTIFICATION
BYTE
ADDRESS
BYTE
1 0 1 0 A2 A1 A0 0
SIGNALS FROM
THE SLAVE
S
T
O
P
DATA
BYTE
0 0 0
A
C
K
A
C
K
A
C
K
FIGURE 29. BYTE WRITE SEQUENCE
SIGNALS
FROM THE
MASTER
S
T
A
R
T
SIGNAL AT SDA
IDENTIFICATION
BYTE WITH
R/W = 0
ADDRESS
BYTE
1 0 1 0 A2 A1 A0 0
SIGNALS FROM
THE SLAVE
S
READ
T
A IDENTIFICATION
BYTE WITH
R
R/W = 1
T
S
A T
C O
K P
A
C
K
1 0 1 0 A2 A1 A0 1
0 0 0
A
C
K
A
C
K
A
C
K
A
C
K
FIRST READ
DATA BYTE
LAST READ
DATA BYTE
FIGURE 30. READ SEQUENCE
Write Operation
Read Operation
A Write operation requires a START condition, followed by a valid
Identification Byte, a valid Address Byte, a Data Byte, and a STOP
condition. After each of the three bytes, the ISL23348 responds
with an ACK. The data is transferred from I2C block to the
corresponding register at the 9th clock of the data byte and
device enters its standby state (see Figures 28 and 29).
A Read operation consists of a three byte instruction followed by
one or more Data Bytes (see Figure 30). The master initiates the
operation issuing the following sequence: a START, the
Identification byte with the R/W bit set to “0”, an Address Byte, a
second START, and a second Identification byte with the R/W bit
set to “1”. After each of the three bytes, the ISL23348 responds
with an ACK; then the ISL23348 transmits Data Byte. The master
terminates the read operation issuing a NACK (ACK) and a STOP
condition following the last bit of the last Data Byte (see
Figure 30).
It is possible to perform a sequential Write to all DCP channels
via a single Write operation. The command is initiated by sending
an additional Data Byte after the first Data byte instead of
sending a STOP condition.
FN7903 Rev 1.00
August 24, 2011
Page 16 of 19
ISL23348
Applications Information
Wiper Transition
VLOGIC Requirements
When stepping up through each tap in voltage divider mode,
some tap transition points can result in noticeable voltage
transients, or overshoot/undershoot, resulting from the sudden
transition from a very low impedance “make” to a much higher
impedance “break” within a short period of time (
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