N57L5125
www.onsemi.com
5
FUNCTIONAL DESCRIPTION
The N57L5125 consists of a fixed resistor and a wiper
contact with 32−tap points that are digitally controlled
through a 2-wire up/down serial interface. Three end-to-end
resistance values are available: 10 kW, 50 kW and 100 kW.
The N57L5125 is designed to operate as a potentiometer.
In this configuration, the low terminal of the resistor array
is connected to ground (pin 2).
Digital Interface Operation
The devices have two modes of operation when the serial
interface is active: increment and decrement mode. The
serial interface is only active when CS
is low.
The CS
and U/D inputs control the position of the wiper
along the resistor array. When CS
transitions from high to
low, the part will go into increment mode if U/D
input is
high, and into decrement mode when U/D
input is low. Once
the mode is set, the device will remain in that mode until CS
goes high again. A low-to-high transition at the U/D pin will
increment or decrement the wiper position depending on the
current mode (Figures 5 and 6).
When the CS
input transitions to high (serial interface
inactive), the value of the counter is stored and the wiper
position is maintained.
Note that when the wiper reaches the maximum (or
minimum) tap position, the wiper will not wrap around to the
minimum (or maximum) position.
Power-On Reset
All parts in this family feature power-on reset (POR)
circuitry that sets the wiper position to midscale at
power-up. By default, the chip is in the increment mode.
Figure 5. Serial Interface Timing Diagram, Increment Mode
W
U/D
CS
t
CU
t
CI
t
IL
t
IH
t
SETTLE
t
SETTLE
t
IC
Note: “W” is not a digital signal. It represents wiper transitions.
Figure 6. Serial Interface Timing Diagram, Decrement Mode
W
Note: “W” is not a digital signal. It represents wiper transitions.
t
SETTLE
t
CI
t
CU
U/D
CS
t
IH
t
IL
t
SETTLE
t
IC
