SUMMIT S9518P, S9518S Datasheet
© SUMMIT MICROELECTRONICS, Inc. 2000 • 300 Orchard City Drive, Suite 131 • Campbell, CA 95008 • Phone 408-378-6461 • Fax 408-378-6586 • www.summitmicro.com
1
Characteristics subject to change without notice
SUMMIT
MICROELECTRONICS, Inc.
2017 5.2 8/2/00
S9518
FEATURES
Digitally Controlled Electronic Potentiometer
• 8-Bit Digital-to-Analog Converter (DAC)
– Independent Reference Inputs
– Differential Non-Linearity of ±0.5LSB max
– Integral Non-Linearity of ±1LSB max
•V
OUT
Value in EEPROM for Power-On Recall
– Equivalent to 256-Step Potentiometer
• Unity Gain Op Amp Drives up to 1mA
• Simple Trimming Adjustment
– Debounced Pushbutton Interface
• Low Noise Operation
• “Clickless” Transitions between DAC Steps
• No Mechanical Wear-out Problem
– 1,000,000 Stores (typical)
– 100 Year Data Retention
• Operation from 2.7V to 5.5V Supply
• Low Power: 1mW max at 5V
Nonvolatile DACPOT™ Electronic Potentiometer
With Debounced Push Button Interface
OVERVIEW
The S9518 DACPOT trimmer is an 8-bit nonvolatile DAC
designed to replace mechanical potentiometers. The
S9518 includes a unity-gain amplifier to buffer the DAC
output and enables V
OUT
to swing from rail to rail. The
DACPOT trimmer operates over a supply voltage range of
2.7V to 5.5V.
The S9518’s simple pushbutton input provides an ideal
interface for operator adjusted equipment. This interface
allows for quick and easy adjustment of even the most
sophisticated systems.
The S9518 is a pin-compatible performance upgrade for
other industry nonvolatile potentiometers. The S9518
offers double the resolution of these devices and provides
‘clickless’ transitions of V
OUT
.
FUNCTIONAL BLOCK DIAGRAM
DWN#
V
DD
8
2
V
OUT
5
8-Bit
E2PROM
VL
6
VH
3
8-Bit Data
Register
Debounce Circuit
& Write Control
Logic
8-Bit DAC
UP#
1
STR#
7
GND
4
2017 T BD 5.0
2
S9518
SUMMIT MICROELECTRONICS, Inc.
2017 5.2 8/2/00
Analog Section
The S9518 is an 8-bit, voltage output digital-to-analog
converter (DAC). The DAC consists of a resistor network
that converts 8-bit digital values into equivalent analog
output voltages in proportion to the applied reference
voltage.
Reference Inputs
The voltage differential between the VL and VH inputs sets
the full-scale output voltage range. VL must be equal to or
greater than ground (a positive voltage). VH must be
greater than VL and less than or equal to VDD. See
specifications for guaranteed operating limits.
Output Buffer Amplifier
The voltage output is from a precision unity-gain follower
that can slew up to 1V/µs.
Digital Interface
The interface provides simple pushbutton control of an
up/down counter that drives the DAC. The DAC output is
a ratiometric voltage output.
UP# is an active low pushbutton input. An internal pull-up
resistor, with nominal value of 50kΩ, eliminates an external resistor. A 30ms debounce period is included in the
input timing to prevent multiple pulsing of the counter.
Either a switch closure to ground or a low logic level will,
after the debounce time, change the potentiometer tap
position. UP# moves the output voltage towards the V
H
reference input.
If the UP# pushbutton is kept depressed the counter will
continue to increment at the rate of one count every
250ms for one second. After one second the counter
increments faster, one count every 50ms, until the
pushbutton is released. Changes to the DAC output using
the UP# input do not alter the data stored in EEPROM.
PINOUT
DWN# is an active low pushbutton input that decrements
the counter and moves the potentiometer output voltage
towards the VL reference input. The DWN# control input
also includes an internal 50kΩ pull-up resistor and a 30ms
debounce period to prevent multiple pulsing. A low logic
level will also change the potentiometer tap position after
the debounce period.
If the DWN# pushbutton is kept depressed the counter
continues to decrement at the rate of one count every
250ms for one second. After one second the counter
decrements at one count every 50ms until the pushbutton
is released. Changes to the DAC output using the DWN#
input do not alter the data stored in EEPROM.
STR# This input can be used in two ways:
1) If the input is tied low, then AUTOSTORE is enabled.
When VDD powers down, an automatic store cycle
takes place that updates the nonvolatile EEPROM
memory.
2) STR# is an active low pushbutton input that also
updates the nonvolatile memory. The input is
debounced but does not have an internal pull-up
resistor. For every valid push the S9518 will store the
current potentiometer position to EEPROM.
PIN NAMES
UP#
DWN#
VH
GND
V
DD
STR#
VL
V
OUT
1
2
3
4
8
7
6
5
8-Pin PDIP
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S9518
3
SUMMIT MICROELECTRONICS, Inc.
2017 5.2 8/2/00
There are five main blocks to the S9518: an 8-bit EEPROM memory; input debounce circuits, control logic,
and 8-bit counter; 8-bit data register; decode section and
resistor ladder (DAC); and the buffer amplifier.
The input control section operates just like an up/down
counter. The output of this counter is fed to the data
register and then decoded to activate one of 255 electronic
switches connected to the resistor ladder. The ladder is
comprised of 256 resistors of equal value connected in
series. At the bottom of the ladder and at the junctions of
the resistors there are electronic switches that transfer the
voltage at each point to the buffer amplifier and then to the
output.
The S9518 is designed to interface directly to two
pushbutton switches that effectively move the potentiometer wiper up or down. The UP# and DWN# inputs,
respectively, increment or decrement the 8-bit counter.
The data input to the DAC is decoded to select one of the
256 wiper positions along the resistive ladder. The wiper
increment input UP# and the wiper decrement input
DWN# are connected to internal pull-ups so that they
normally remain high. When pulled low by an external
pushbutton switch or a logic low level input, the wiper will
be switched to the next adjacent tap position. Internal
debounce circuitry prevents inadvertent switching of the
wiper position if UP# or DWN# remain low for less than
30ms (typical).
Each of the buttons can be pushed either once for a single
increment/decrement or held low continuously for multiple
increments/decrements. The number of increments/decrements of the wiper position depends on how long the
button is pushed. When making a continuous push, after
the first second, the increment/decrement speed increases. For the first second the device will be in the slow
scan mode. Then, if the button is held for longer than one
second, the device will go into the fast scan mode. As soon
as the button is released the S9518 will return to a standby
condition.
The DAC, whether set to 00
HEX
or FF
HEX
, acts like its
mechanical equivalent and does not move beyond the last
position. That is, the counter does not wrap around when
clocked up to FF
HEX
or down to 00
HEX
.
AUTOSTORE
The value of the counter is stored in EEPROM memory
whenever the chip senses a power-down of VDD while
STR# is enabled (held low). When power is restored the
contents of the memory are recalled and the counter reset
to the last value stored. If AUTOSTORE is to be implemented, STR# is typically hard wired to GND. If STR# is
held high during power-up and then taken low the wiper will
not respond to the UP# or DWN# inputs until STR# is
brought high and the store is complete. See Figure 1.
Manual (Pushbutton) Store
When STR# is not enabled (held high) a pushbutton switch
may be used to pull STR# low and released to perform a
manual store of the wiper position in EEPROM memory.
See Figure 2.
Effect of VDD Removal
The resistor ladder, connected between VH and VL, does
not change value when VDD is removed. However, the
buffer amplifier no longer functions, and consequently a
high impedance appears at the V
OUT
pin.
Figure 2: Typical circuit with STR store pin
controlled by push button switch
Figure 1: Typical circuit with STR store pin used in
AUTOSTORE mode
DEVICE OPERATION
UP#
DWN#
V
H
GND
V
DD
STR#
V
L
V
OUT
8
7
6
5
1
2
3
4
V
DD
20kΩ
2017 T Fig02 5.0
UP#
DWN#
V
H
GND
V
DD
STR#
V
L
V
OUT
8
7
6
5
1
2
3
4
V
DD
22µF
2017 T Fig01 5.1
470Ω
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