1CAUTION: These devices are sensitive to electrostatic discharge; follow proper IC Handling Procedures.
1-888-INTERSIL or 1-888-468-3774 |Copyright Intersil Americas Inc. 2011. All Rights Reserved
Intersil (and design) and XDCP are trademarks owned by Intersil Corporation or one of its subsidiaries.
All other trademarks mentioned are the property of their respective owners
Dual, 128-Tap, Low Voltage Digitally Controlled
Potentiometer (XDCP™)
ISL23428
The ISL23428 is a volatile, low voltage, low noise, low power,
128-tap, dual digitally controlled potentiometer (DCP) with an
SPI Bus™ interface. It integrates two DCP cores, wiper switches
and control logic on a monolithic CMOS integrated circuit.
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
SPI bus interface. Each potentiometer has an associated
volatile Wiper Register (WRi, i = 0, 1) 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).
The low voltage, low power consumption, and small package
of the ISL23428 make it an ideal choice for use in battery
operated equipment. In addition, the ISL23428 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 ISL23428 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.
Applications
• Power supply margining
• Trimming sensor circuits
• Gain adjustment in battery powered instruments
• RF power amplifier bias compensation
Features
• Two potentiometers per package
•128 resistor taps
•10k 50kor 100k total resistance
• SPI serial interface
- No additional level translator for low bus supply
- Daisy Chaining of multiple DCPs
•Power supply
-V
CC = 1.7V to 5.5V analog power supply
-V
LOGIC = 1.2V to 5.5V SPI bus/logic power supply
• Maximum supply current without serial bus activity
(standby)
- 4µA @ VCC and VLOGIC = 5V
- 1.7µA @ 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
• Wiper resistance: 70 typical @ VCC = 3.3V
• Power-on preset to mid-scale (64 tap position)
• Extended industrial temperature range: -40°C to +125°C
• 14 Ld TSSOP or 16 Ld UTQFN packages
• Pb-free (RoHS compliant)
FIGURE 1. FORWARD AND BACKWARD RESISTANCE vs TAP
POSITION, 10kΩ DCP
FIGURE 2. VREF ADJUSTMENT
0
2000
4000
6000
8000
10000
0326496128
TAP POSITION (DECIMAL)
RESISTANCE (Ω)
VREF_M
ISL28114
ISL23428 +
-
VREF
RL
RW
RH
August 25, 2011
FN7904.0
ISL23428
2FN7904.0
August 25, 2011
Block Diagram
POWER UP
INTERFACE,
CONTROL
AND
STATUS
LOGIC
SPI
INTERFACE
VCC
GND
SCK
SDI
SDO
CS
RH0
RL0RW0
RH1
RL1RW1
WR0
VOLATILE
REGISTER
AND
WIPER
CONTROL
CIRCUITRY
WR1
VOLATILE
REGISTER
AND
WIPER
CONTROL
CIRCUITRY
VLOGIC
Pin Configurations
ISL23428
(14 LD TSSOP)
TOP VIEW
ISL23428
(16 LD UTQFN)
TOP VIEW
RW1
RL1
RL0
VCC
RH1
RH0
SDI
CS
SCK
RW0
VLOGIC
GND
GND
SDO
1
2
3
4
5
6
7
14
13
12
11
10
9
8
GND VLOGIC
RH1
GND
NC
RL1
RW1
VCC
CS
RW0
SCK RH0
RL0
SDO
SDI
1
3
4
15
16
14
13
2
12
10
9
11
6
5
7
8
GND
Pin Descriptions
TSSOP UTQFN SYMBOL DESCRIPTION
1, 7 5, 6, 15 GND Ground pin
216V
LOGIC SPI bus/logic supply
Range 1.2V to 5.5V
3 1 SDO Logic Pin - Serial bus data output
(configurable)
4 2 SCK Logic Pin - Serial bus clock input
5 3 SDI Logic Pin - Serial bus data input
64 CS
Logic Pin - Active low chip select
8 8 RL1 DCP1 “low” terminal
99RW1DCP1 wiper terminal
10 10 RH1 DCP1 “high” terminal
11 11 RH0 DCP0 “high” terminal
12 12 RW0 DCP0 wiper terminal
13 13 RL0 DCP0 “low” terminal
14 14 VCC Analog power supply.
Range 1.7V to 5.5V
7 NC Not Connected
ISL23428
3FN7904.0
August 25, 2011
Ordering Information
PART NUMBER
(Note 4)
PART
MARKING
RESISTANCE
OPTION
(kΩ)
TEMP RANGE
(°C)
PACKAGE
(Pb-free)
PKG.
DWG. #
ISL23428TFVZ (Note 2) 23428 TFVZ 100 -40 to +125 14 Ld TSSOP M14.173
ISL23428TFVZ-T7A (Notes 1, 2) 23428 TFVZ 100 -40 to +125 14 Ld TSSOP M14.173
ISL23428TFVZ-TK (Notes 1, 2) 23428 TFVZ 100 -40 to +125 14 Ld TSSOP M14.173
ISL23428UFVZ (Note 2) 23428 UFVZ 50 -40 to +125 14 Ld TSSOP M14.173
ISL23428UFVZ-T7A (Notes 1, 2) 23428 UFVZ 50 -40 to +125 14 Ld TSSOP M14.173
ISL23428UFVZ-TK (Notes 1, 2) 23428 UFVZ 50 -40 to +125 14 Ld TSSOP M14.173
23425WFVZ (Note 2) 23428 WFVZ 10 -40 to +125 14 Ld TSSOP M14.173
23425WFVZ-T7A (Notes 1, 2) 23428 WFVZ 10 -40 to +125 14 Ld TSSOP M14.173
23425WFVZ-TK (Notes 1, 2) 23428 WFVZ 10 -40 to +125 14 Ld TSSOP M14.173
ISL23428TFRUZ-T7A (Notes 1, 3) GBR 100 -40 to +125 16 Ld 2.6x1.8 UTQFN L16.2.6x1.8A
ISL23428TFRUZ-TK (Notes 1, 3) GBR 100 -40 to +125 16 Ld 2.6x1.8 UTQFN L16.2.6x1.8A
ISL23428UFRUZ-T7A (Notes 1, 3) GBP 50 -40 to +125 16 Ld 2.6x1.8 UTQFN L16.2.6x1.8A
ISL23428UFRUZ-TK (Notes 1, 3) GBP 50 -40 to +125 16 Ld 2.6x1.8 UTQFN L16.2.6x1.8A
ISL23428WFRUZ-T7A (Notes 1, 3) GBN 10 -40 to +125 16 Ld 2.6x1.8 UTQFN L16.2.6x1.8A
ISL23428WFRUZ-TK (Notes 1, 3) GBN 10 -40 to +125 16 Ld 2.6x1.8 UTQFN L16.2.6x1.8A
NOTES:
1. 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. These Intersil Pb-free plastic packaged products employ special Pb-free material sets; molding compounds/die attach materials and NiPdAu plate-e4
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
4. For Moisture Sensitivity Level (MSL), please see device information page for ISL23428. For more information on MSL please see techbrief TB363.
ISL23428
4FN7904.0
August 25, 2011
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) . . . . . . . . . . . . . . .4.5kV
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)
14 Ld TSSOP Package (Notes 5, 6) . . . . . . 112 40
16 Ld UTQFN Package (Notes 5, 6) . . . . . . 110 64
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:
5. JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details.
6. For JC, the “case temp” location is the center top of the package.
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 PARAMETER TEST CONDITIONS
MIN
(Note 19)
TYP
(Note 7)
MAX
(Note 19) UNITS
RTOTAL RH to RL Resistance W option 10 kΩ
U option 50 kΩ
T option 100 kΩ
RH to RL Resistance Tolerance -20 ±2 +20 %
End-to-End Temperature Coefficient W option 125 ppm/°C
U option 65 ppm/°C
T option 45 ppm/°C
VRH, VRL DCP Terminal Voltage VRH or VRL to GND 0V
CC V
RWWiper Resistance RH - floating, VRL = 0V, force IW current to
the wiper, IW = (VCC - VRL)/RTOTAL,
VCC = 2.7V to 5.5V
70 200 Ω
VCC = 1.7V 580 Ω
CH/CL/CWTerminal Capacitance See “DCP Macro Model” on page 9 32/32/32 pF
ILkgDCP Leakage on DCP Pins Voltage at pin from GND to VCC -0.4 <0.1 0.4 µA
Noise Resistor Noise Density Wiper at middle point, W option 16 nV/√Hz
Wiper at middle point, U option 49 nV/√Hz
Wiper at middle point, T option 61 nV/√Hz
Feed Thru Digital Feed-through from Bus to Wiper Wiper at middle point -65 dB
PSRR Power Supply Reject Ratio Wiper output change if VCC change
±10%; wiper at middle point
-75 dB
ISL23428
5FN7904.0
August 25, 2011
VOLTAGE DIVIDER MODE (0V @ RL; VCC @ RH; measured at RW, unloaded)
INL
(Note 12)
Integral Non-linearity, Guaranteed
Monotonic
W option -0.5 ±0.15 +0.5 LSB
(Note 8)
U, T option -0.5 ±0.15 +0.5 LSB
(Note 8)
DNL
(Note 11)
Differential Non-linearity, Guaranteed
Monotonic
W option -0.5 ±0.15 +0.5 LSB
(Note 8)
U, T option -0.5 ±0.15 +0.5 LSB
(Note 8)
FSerror
(Note 10)
Full-scale Error W option -3 -1.5 0LSB
(Note 8)
U, T option -1.5 -0.9 0LSB
(Note 8)
ZSerror
(Note 9)
Zero-scale Error W option 01.5 3LSB
(Note 8)
U, T option 00.9 1.5 LSB
(Note 8)
Vmatch
(Note 21)
DCP to DCP Matching DCPs at same tap position, same voltage
at all RH terminals, and same voltage at
all RL terminals
-2 ±0.5 2LSB
(Note 8)
TCV
(Note 13)
Ratiometric Temperature Coefficient W option, Wiper Register set to 40 hex 8 ppm/°C
U option, Wiper Register set to 40 hex 4 ppm/°C
T option, Wiper Register set to 40 hex 2.3 ppm/°C
tLS_Settling Large Signal Wiper Settling Time From code 0 to 7F hex, measured from 0
to 1 LSB settling of the wiper
300 ns
fcutoff -3dB Cutoff Frequency Wiper at middle point W option 1200 kHz
Wiper at middle point U option 250 kHz
Wiper at middle point T option 120 kHz
RHEOSTAT MODE (Measurements between RW and RL pins with RH not connected, or between RW and RH with RL not connected)
RINL
(Note 17)
Integral Non-Linearity, Guaranteed
Monotonic
W option; VCC = 2.7V to 5.5V -1.0 ±0.5 +1.0 MI
(Note 14)
W option; VCC = 1.7V 4 MI
(Note 14)
U, T option; VCC = 2.7V to 5.5V -0.5 ±0.15 +0.5 MI
(Note 14)
U, T option; VCC = 1.7V 1 MI
(Note 14)
RDNL
(Note 16)
Differential Non-Linearity, Guaranteed
Monotonic
W option; VCC = 2.7V to 5.5V -0.5 ±0.15 +0.5 MI
(Note 14)
W option; VCC = 1.7V ±0.4 MI
(Note 14)
U, T option; VCC = 2.7V to 5.5V -0.5 ±0.15 +0.5 MI
(Note 14)
U, T option; VCC = 1.7V ±0.4 MI
(Note 14)
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. (Continued)
SYMBOL PARAMETER TEST CONDITIONS
MIN
(Note 19)
TYP
(Note 7)
MAX
(Note 19) UNITS
ISL23428
6FN7904.0
August 25, 2011
Roffset
(Note 15)
Offset, Wiper at 0 Position W option; VCC = 2.7V to 5.5V 01.8 3MI
(Note 14)
W option; VCC = 1.7V 3 MI
(Note 14)
U, T option; VCC = 2.7V to 5.5V 00.3 1MI
(Note 14)
U, T option; VCC = 1.7V 0.5 MI
(Note 14)
Rmatch
(Note 22)
DCP to DCP Matching Any two DCPs at the same tap position
with the same terminal voltages
-2 ±0.5 2LSB
(Note 8)
TCR
(Note 18)
Resistance TemperatureCoefficient W option; Wiper register set between 19
hex and 7F hex
170 ppm/°C
U option; Wiper register set between 19
hex and 7F hex
80 ppm/°C
T option; Wiper register set between 19
hex and 7F hex
50 ppm/°C
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. (Continued)
SYMBOL PARAMETER TEST CONDITIONS
MIN
(Note 19)
TYP
(Note 7)
MAX
(Note 19) UNITS
Operating 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 PARAMETER TEST CONDITIONS
MIN
(Note 19)
TYP
(Note 7)
MAX
(Note 19) UNITS
ILOGIC VLOGIC Supply Current (Write/Read) VLOGIC = 5.5V, VCC = 5.5V,
fSCK = 5MHz (for SPI active read and write)
1.5 mA
VLOGIC = 1.2V, VCC = 1.7V,
fSCK = 1MHz (for SPI active read and write)
30 µA
ICC VCC Supply Current (Write/Read) VLOGIC = 5.5V, VCC = 5.5V 100 µA
VLOGIC = 1.2V, VCC = 1.7V 10 µA
ILOGIC SB VLOGIC Standby Current VLOGIC = VCC = 5.5V,
SPI interface in standby
2µA
VLOGIC = 1.2V, VCC = 1.7V,
SPI interface in standby
0.5 µA
ICC SB VCC Standby Current VLOGIC = VCC = 5.5V,
SPI interface in standby
2µA
VLOGIC = 1.2V, VCC = 1.7V,
SPI interface in standby
1.2 µA
ILOGIC
SHDN
VLOGIC Shutdown Current VLOGIC = VCC = 5.5V,
SPI interface in standby
2µA
VLOGIC = 1.2V, VCC = 1.7V,
SPI interface in standby
0.5 µA
ICC SHDN VCC Shutdown Current VLOGIC = VCC = 5.5V,
SPI interface in standby
2µA
VLOGIC = 1.2V, VCC = 1.7V,
SPI interface in standby
1.2 µA
ILkgDig Leakage Current, at Pins CS, SDO, SDI, SCK Voltage at pin from GND to VLOGIC -0.4 <0.1 0.4 µA
ISL23428
7FN7904.0
August 25, 2011
tDCP Wiper Response Time W option; CS rising edge to wiper new
position, from 10% to 90% of final value.
0.4 µs
U option; CS rising edge to wiper new
position, from 10% to 90% of final value.
1.5 µs
T option; CS rising edge to wiper new
position, from 10% to 90% of final value.
3.5 µs
tShdnRec DCP Recall Time from Shutdown Mode CS rising edge to wiper recalled position
and RH connection
1.5 µs
VCC, VLOGIC
Ramp
VCC ,VLOGIC Ramp Rate (Note 20) Ramp monotonic at any level 0.01 50 V/ms
Serial Interface Specification For SCK, SDI, SDO, CS Unless Otherwise Noted.
SYMBOL PARAMETER TEST CONDITIONS
MIN
(Note 19)
TYP
(Note 7)
MAX
(Note 19) UNITS
VIL Input LOW Voltage -0.3 0.3 x VLOGIC V
VIH Input HIGH Voltage 0.7 x VLOGIC VLOGIC+ 0.3 V
Hysteresis SDI and SCK Input Buffer
Hysteresis
VLOGIC > 2V 0.05 x VLOGIC V
VLOGIC < 2V 0.1 x VLOGIC V
VOL SDO Output Buffer LOW Voltage IOL = 3mA, VLOGIC > 2V 0 0.4 V
IOL = 1.5mA, VLOGIC < 2V 0.2 x VLOGIC V
Rpu SDO Pull-Up Resistor Off-Chip Maximum is determined by
tRO and tFO with maximum
bus load Cb = 30pF,
fSCK =5MHz
1.5 kΩ
Cpin SCK, SDO, SDI, CS Pin Capacitance 10 pF
fSCK SCK Frequency VLOGIC = 1.7V to 5.5V 5 MHz
VLOGIC = 1.2V to 1.6V 1 MHz
tCYC SPI Clock Cycle Time VLOGIC ≥ 1.7V 200 ns
tWH SPI Clock High Time VLOGIC ≥ 1.7V 100 ns
tWL SPI Clock Low Time VLOGIC ≥ 1.7V 100 ns
tLEAD Lead Time VLOGIC ≥ 1.7V 250 ns
tLAG Lag Time VLOGIC ≥ 1.7V 250 ns
tSU SDI, SCK and CS Input Setup Time VLOGIC ≥ 1.7V 50 ns
tHSDI, SCK and CS Input Hold Time VLOGIC ≥ 1.7V 50 ns
tRI SDI, SCK and CS Input Rise Time VLOGIC ≥ 1.7V 10 ns
tFI SDI, SCK and CS Input Fall Time VLOGIC ≥ 1.7V 10 20 ns
tDIS SDO Output Disable Time VLOGIC ≥ 1.7V 0 100 ns
tSO SDO Output Setup Time VLOGIC ≥ 1.7V 50 ns
tVSDO Output Valid Time VLOGIC ≥ 1.7V 150 ns
tHO SDO Output Hold Time VLOGIC ≥ 1.7V 0 ns
Operating 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. (Continued)
SYMBOL PARAMETER TEST CONDITIONS
MIN
(Note 19)
TYP
(Note 7)
MAX
(Note 19) UNITS
ISL23428
8FN7904.0
August 25, 2011
tRO SDO Output Rise Time Rpu = 1.5k, Cbus = 30pF 60 ns
tFO SDO Output Fall Time Rpu = 1.5k, Cbus = 30pF 60 ns
tCS CS Deselect Time 2 µs
NOTES:
7. Typical values are for TA = +25°C and 3.3V supply voltages.
8. 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.
9. ZS error = V(RW)0/LSB.
10. FS error = [V(RW)127 – VCC]/LSB.
11. DNL = [V(RW)i – V(RW)i-1]/LSB-1, for i = 1 to 127. i is the DCP register setting.
12. INL = [V(RW)i – i • LSB – V(RW)0]/LSB for i = 1 to 127
13. for i = 8 to 127decimal, T = -40°C to +125°C. Max( ) is the maximum value of the wiper voltage
and Min( ) is the minimum value of the wiper voltage over the temperature range.
14. 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.
15. Roffset = RW0/MI, when measuring between RW and RL.
Roffset = RW127/MI, when measuring between RW and RH.
16. RDNL = (RWi – RWi-1)/MI -1, for i = 8 to 127.
17. RINL = [RWi – (MI • i) – RW0]/MI, for i = 8 to 127.
18. for i = 8 to 127, T = -40°C to +125°C. Max( ) is the maximum value of the resistance and Min( ) is the
minimum value of the resistance over the temperature range.
19. Compliance to datasheet limits is assured by one or more methods: production test, characterization and/or design.
20. 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.
21. VMATCH = [V(RWx)i - V(RWy)i]/LSB, for i = 1 to 127, x = 0 to 1 and y = 0 to 1.
22. RMATCH = (RWi,x - RWi,y)/MI, for i = 1 to 127, x = 0 to 1 and y = 0 to 1.
Serial Interface Specification For SCK, SDI, SDO, CS Unless Otherwise Noted. (Continued)
SYMBOL PARAMETER TEST CONDITIONS
MIN
(Note 19)
TYP
(Note 7)
MAX
(Note 19) UNITS
TCV
Max V RW
i
Min V RW
i
–
VRW
i+25°C
------------------------------------------------------------------------------106
+165°C
---------------------
=
TCR
Max RiMin Ri–
Ri +25°C
-------------------------------------------------------106
+165°C
---------------------
=
ISL23428
9FN7904.0
August 25, 2011
DCP Macro Model
Timing Diagrams
32pF
RH
RTOTAL
CH
32pF
CW
CL
32pF
RW
RL
Input Timing
Output Timing
XDCP™ Timing (for All Load Instructions)
...
CS
SCK
SDI
SDO
MSB LSB
tLEAD
tH
tSU tFI
tCS
tLAG
tCYC
tWL
...
tRI
tWH
...
CS
SCK
SDO
SDI ADDR
MSB LSB
tDIS
tHO
tV
...
tSO
...
CS
SCK
SDI MSB LSB
VW
tDCP
...
SDO
*When CS is HIGH
SDO at Z or Hi-Z state
ISL23428
10 FN7904.0
August 25, 2011
Typical Performance Curves
FIGURE 3. 10kΩ DNL vs TAP POSITION, VCC = 3.3V, +25°C FIGURE 4. 50kΩ DNL vs TAP POSITION, VCC = 3.3V, +25°C
FIGURE 5. 10kΩ INL vs TAP POSITION, VCC = 3.3V, +25°C FIGURE 6. 50kΩ INL vs TAP POSITION, VCC = 3.3V, +25°C
FIGURE 7. 10kΩ RDNL vs TAP POSITION, VCC = 3.3V, +25°C FIGURE 8. 50kΩ RDNL vs TAP POSITION, VCC = 3.3V, +25°C
-0.20
-0.10
0.00
0.10
0.20
0 326496128
TAP POSITION (DECIMAL)
DNL (LSB)
-0.04
-0.02
0.00
0.02
0.04
0326496128
TAP POSITION (DECIMAL)
DNL (LSB)
-0.30
-0.15
0.00
0.15
0.30
0 326496128
TAP POSITION (DECIMAL)
INL (LSB)
0.00
0.03
0.06
0.09
0.12
0326496128
TAP POSITION (DECIMAL)
INL (LSB)
-0.20
-0.10
0.00
0.10
0.20
0 326496128
TAP POSITION (DECIMAL)
RDNL (MI)
-0.04
-0.02
0.00
0.02
0.04
0 32 64 96 128
TAP POSITION (DECIMAL)
RDNL (MI)
ISL23428
11 FN7904.0
August 25, 2011
FIGURE 9. 10kΩ RINL vs TAP POSITION, VCC = 3.3V, +25°C FIGURE 10. 50kΩ RINL vs TAP POSITION, VCC = 3.3V, +25°C
FIGURE 11. 10kΩ WIPER RESISTANCE vs TAP POSITION, VCC = 3.3V FIGURE 12. 50kΩ WIPER RESISTANCE vs TAP POSITION, VCC = 3.3V
FIGURE 13. 10kΩ TCv vs TAP POSITION, VCC = 3.3V FIGURE 14. 50kΩ TCv vs TAP POSITION, VCC = 3.3V
Typical Performance Curves (Continued)
-0.30
-0.15
0.00
0.15
0.30
0326496128
TAP POSITION (DECIMAL)
RINL (MI)
-0.08
-0.04
0.00
0.04
0.08
0 32 64 96 128
TAP POSITION (DECIMAL)
RINL (MI)
0
20
40
60
80
100
0 326496128
TAP POSITION (DECIMAL)
WIPER RESISTANCE ()
+125°C
-40°C
+25°C
0
20
40
60
80
100
120
0 32 64 96 128
TAP POSITION (DECIMAL)
WIPER RESISTANCE ()
+125°C
-40°C
+25°C
0
50
100
150
200
15 43 71 99 127
TAP POSITION (DECIMAL)
TCv (ppm/°C)
0
10
20
30
40
15 43 71 99 127
TAP POSITION (DECIMAL)
TCv (ppm/°C)
ISL23428
12 FN7904.0
August 25, 2011
FIGURE 15. 10kΩ TCr vs TAP POSITION FIGURE 16. 50kΩ TCr vs TAP POSITION, VCC = 3.3V
FIGURE 17. 100kΩ TCv vs TAP POSITION, VCC = 3.3V FIGURE 18. 100kΩ TCr vs TAP POSITION, VCC = 3.3V
FIGURE 19. WIPER DIGITAL FEED-THROUGH FIGURE 20. WIPER TRANSITION GLITCH
Typical Performance Curves (Continued)
0
100
200
300
400
500
15 43 71 99 127
TCr (ppm/°C)
TAP POSITION (DECIMAL)
0
30
60
90
120
15 43 71 99 127
TCr (ppm/°C)
TAP POSITION (DECIMAL)
0
5
10
15
20
15 43 71 99 127
TCv (ppm/°C)
TAP POSITION (DECIMAL)
0
30
60
90
120
15 43 71 99 127
TCr (ppm/°C)
TAP POSITION (DECIMAL)
SCK CLOCK
RW PIN
CH1: 1V/DIV, 1µs/DIV
CH2: 10mV/DIV, 1µs/DIV
CH1: 20mV/DIV, 2µs/DIV
CH2: 2V/DIV, 2µs/DIV
WIPER
CS RISING
ISL23428
13 FN7904.0
August 25, 2011
Functional Pin Descriptions
Potentiometers Pins
RHI AND RLI
The high (RHi, i = 0, 1) and low (RLi, i = 0, 1) terminals of the
ISL23428 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) 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.
Power Pins
VCC
Power terminal for the potentiometer section analog power
source. Can be any value needed to support voltage range of DCP
pins, from 1.7V to 5.5V, independent of the VLOGIC voltage.
Bus Interface Pins
SERIAL CLOCK (SCK)
This input is the serial clock of the SPI serial interface.
SERIAL DATA INPUT (SDI)
The SDI is a serial data input pin for SPI interface. It receives
operation code, wiper address and data from the SPI remote
host device. The data bits are shifted in at the rising edge of the
serial clock SCK, while the CS input is low.
FIGURE 21. WIPER LARGE SIGNAL SETTLING TIME FIGURE 22. POWER-ON START-UP IN VOLTAGE DIVIDER MODE
FIGURE 23. 10kΩ -3dB CUT OFF FREQUENCY FIGURE 24. STANDBY CURRENT vs TEMPERATURE
Typical Performance Curves (Continued)
1V/DIV
0.2µs/DIV
WIPER
CS RISING
0.5V/DIV
20µs/DIV VCC
WIPER
0.5V/DIV, 0.2µs/DIV
-3dB FREQUENCY = 1.4MHz AT MIDDLE TAP
CH1: RH TERMINAL
CH2: RW TERMINAL
0
0.2
0.4
0.6
0.8
1.0
1.8
-40 -15 10 35 60 85 110
STANDBY CURRENT I
CC
(µA)
TEMPERATURE (°C)
VCC = 5.5V, VLOGIC = 5.5V
VCC = 1.7V, VLOGIC = 1.2V
1.6
1.4
1.2
ISL23428
14 FN7904.0
August 25, 2011
SERIAL DATA OUTPUT (SDO)
The SDO is a serial data output pin. During a read cycle, the data
bits are shifted out on the falling edge of the serial clock SCK and
will be available to the master on the following rising edge of SCK.
The output type is configured through ACR[1] bit for Push-Pull or
Open Drain operation. Default setting for this pin is Push-Pull. An
external pull-up resistor is required for Open Drain output
operation. When CS is HIGH, the SDO pin is in tri-state (Z) or
high-tri-state (Hi-Z) depends on the selected configuration.
CHIP SELECT (CS)
CS LOW enables the ISL23428, placing it in the active power
mode. A HIGH to LOW transition on CS is required prior to the
start of any operation after power-up. When CS is HIGH, the
ISL23428 is deselected and the SDO pin is at high impedance,
and the device will be in the standby state.
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.
Principles of Operation
The ISL23428 is an integrated circuit incorporating two DCPs
with its associated registers and an SPI 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 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 SPI 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 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 WR of a DCP contains all zeroes
(WRi[7:0] = 00h), its wiper terminal (RWi) 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 ISL23428 is being powered up, both 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 SPI serial
interface, as described in the following sections.
Memory Description
The ISL23428 contains three volatile 8-bit registers: Wiper Register
WR0, Wiper Register WR1, and Access Control Register (ACR).
Memory map of ISL23428 is shown in Table 1. The Wiper Register
WR0 at address 0 contains current wiper position of DCP0; the
Wiper Register WR1 at address 1 contains current wiper position of
DCP1. The Access Control Register (ACR) at address 10h contains
information and control bits described in Table 2.
The SDO bit (ACR[1]) configures type of SDO output pin. The
default value of SDO bit is 0 for Push-Pull output. The SDO pin
can be configured as Open Drain output for some applications. In
this case, an external pull-up resistor is required; reference the
“Serial Interface Specification” on page 7.
Shutdown Function
The SHDN bit (ACR[6]) disables or enables shutdown mode for all
DCP channels simultaneously. When this bit is 0, i.e., each DCP is
forced to end-to-end open circuit and each RW shorted to RL
through a 2kΩ serial resistor, as shown in Figure 25. Default value
of the SHDN bit is 1.
TABLE 1. MEMORY MAP
ADDRESS
(hex)
VOLATILE
REGISTER NAME
DEFAULT SETTING
(hex)
10 ACR 40
1WR1 40
0WR0 40
TABLE 2. ACCESS CONTROL REGISTER (ACR)
BIT # 76543210
NAME/
VALUE
0SHDN
00 0 0SDO0
FIGURE 25. DCP CONNECTION IN SHUTDOWN MODE
2kΩ
RW
RL
RH
ISL23428
15 FN7904.0
August 25, 2011
When the device enters shutdown, all current DCP WR settings are
maintained. When the device exits shutdown, the wipers will
return to the previous WR settings after a short settling time
(see Figure 26).
SPI Serial Interface
The ISL23428 supports an SPI serial protocol, mode 0. The
device is accessed via the SDI input and SDO output with data
clocked in on the rising edge of SCK, and clocked out on the
falling edge of SCK. CS must be LOW during communication with
the ISL23428. The SCK and CS lines are controlled by the host or
master. The ISL23428 operates only as a slave device.
All communication over the SPI interface is conducted by
sending the MSB of each byte of data first.
Protocol Conventions
The SPI protocol contains Instruction Byte followed by one or more
Data Bytes. A valid Instruction Byte contains instruction as the three
MSBs, with the following five register address bits (see Table 3).
The next byte sent to the ISL23428 is the Data Byte.
Table 4 contains a valid instruction set for ISL23428.
If the [R4:R0] bits are zero or one, then the read or write is to the
WRi register. If the [R4:R0] are 10000, then the operation is to
the ACR.
FIGURE 26. SHUTDOWN MODE WIPER RESPONSE
POWER-UP
USER PROGRAMMED
MID SCALE = 40H
SHDN ACTIVATED SHDN RELEASED
AFTER SHDN
WIPER VOLTAGE, VRW (V)
SHDN MODE
TIME (s)
WIPER RESTORE TO
THE ORIGINAL POSITION
0
TABLE 3. INSTRUCTION BYTE FORMAT
BIT #76543210
I2 I1 I0 R4 R3 R2 R1 R0
TABLE 4. INSTRUCTION SET
INSTRUCTION SET
OPERATIONI2 I1 I0 R4 R3 R2 R1 R0
000XXXXXNOP
001XXXXXACR READ
011XXXXXACR WRTE
1 0 0 R4R3R2R1R0WRi or ACR READ
1 1 0 R4R3R2R1R0WRi or ACR WRTE
Where X means “do not care”.
ISL23428
16 FN7904.0
August 25, 2011
Write Operation
A write operation to the ISL23428 is a two or more bytes
operation. First, It requires the CS transition from HIGH-to-LOW.
Then the host sends a valid Instruction Byte, followed by one or
more Data Bytes to the SDI pin. The host terminates the write
operation by pulling the CS pin from LOW-to-HIGH. Instruction is
executed on the rising edge of CS (see Figure 27).
Read Operation
A Read operation to the ISL23428 is a four byte operation. First,
It requires the CS transition from HIGH-to-LOW. Then the host
sends a valid Instruction Byte, followed by a “dummy” Data Byte,
NOP Instruction Byte and another “dummy” Data Byte to SDI pin.
The SPI host receives the Instruction Byte (instruction code +
register address) and requested Data Byte from SDO pin on the
rising edge of SCK during third and fourth bytes, respectively. The
host terminates the read by pulling the CS pin from LOW-to-HIGH
(see Figure 28).
FIGURE 27. TWO BYTE WRITE SEQUENCE
CS
SCK
SDI
SDO
WR INSTRUCTION
DATA BYTE
1 3 4 5 7 8 9 1011121314151626
ADDR
FIGURE 28. FOUR BYTE READ SEQUENCE
CS
SCK
SDI
SDO
RD ADDR
NOP
RD ADDR READ DATA
1 8 16 24 32
ISL23428
17 FN7904.0
August 25, 2011
Applications Information
Communicating with ISL23428
Communication with ISL23428 proceeds using SPI interface
through the ACR (address 10000b), WR0 (addresses 00000b)
and WR1 (addresses 00001b) registers.
The wiper of the potentiometer is controlled by the WRi register.
Writes and read