CAT5251_13 Datasheet, PDF (4/15 Pages) ON Semiconductor – Quad Digital Potentiometer (POT)

CAT5251
SERIAL BUS PROTOCOL
The CAT5251 supports the SPI bus data transmission
protocol. The synchronous Serial Peripheral Interface (SPI)
helps the CAT5251 to interface directly with many of
today’s popular microcontrollers. The CAT5251 contains an
8-bit instruction register. The instruction set and the
operation codes are detailed in Table 13, Instruction Set on
page 9.
After the device is selected with CS going low the first
byte will be received. The part is accessed via the SI pin, with
data being clocked in on the rising edge of SCK. The first
byte contains one of the six op-codes that define the
operation to be performed.
DEVICE OPERATION
The CAT5251 is four resistor arrays integrated with an
SPI serial interface logic, four 8-bit wiper control registers
and sixteen 8-bit, non-volatile memory data registers. Each
resistor array contains 255 separate resistive elements
connected in series. The physical ends of each array are
equivalent to the fixed terminals of a mechanical
potentiometer (R_H and R_L). R_H and R_L are symmetrical and
may be interchanged. The tap positions between and at the
ends of the series resistors are connected to the output wiper
terminals (R_W) by a CMOS transistor switch. Only one tap
point for each potentiometer is connected to its wiper
terminal at a time and is determined by the value of the wiper
control register. Data can be read or written to the wiper
control registers or the non-volatile memory data registers
via the SPI bus. Additional instructions allow data to be
transferred between the wiper control registers and each
respective potentiometer’s non-volatile data registers. Also,
the device can be instructed to operate in an “increment/
decrement” mode.
Table 2. ABSOLUTE MAXIMUM RATINGS
Parameter
Ratings
Units
Temperature Under Bias
−55 to +125
C
Storage Temperature
−65 to +150
C
Voltage on any Pin with Respect to V_SS (Notes 1, 2)
V_CC with Respect to Ground
Package Power Dissipation Capability (T_A = 25C)
Lead Soldering Temperature (10 s)
−2.0 to +V_CC +2.0
V
−2.0 to +7.0
V
1.0
W
300
C
Wiper Current
6
mA
Stresses exceeding Maximum Ratings may damage the device. Maximum Ratings are stress ratings only. Functional operation above the
Recommended Operating Conditions is not implied. Extended exposure to stresses above the Recommended Operating Conditions may affect
device reliability.
1. The minimum DC input voltage is –0.5 V. During transitions, inputs may undershoot to –2.0 V for periods of less than 20 ns. Maximum DC
voltage on output pins is V_CC + 0.5 V, which may overshoot to V_CC + 2.0 V for periods of less than 20 ns.
2. Latch-up protection is provided for stresses up to 100 mA on address and data pins from –1 V to V_CC + 1 V.
Table 3. RECOMMENDED OPERATING CONDITIONS
Parameter
V_CC
Operating Ambient Temperature (Industrial)
Ratings
+2.5 V to +6
−40 to +85
Units
V
C
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