CAT523 Datasheet, PDF (6/15 Pages) Catalyst Semiconductor – Configured Digitally Programmable Potentiometer (DPP): Programmable Voltage Applications

CAT523
Not Recommended for New Design
PIN DESCRIPTION
Pin Name Function
1
V_DD
Power supply positive
2
CLK Clock input pin
3 RDY/¯B¯S¯Y¯ Ready/Busy output
4
CS
Chip select
5
DI
Serial data input pin
6
DO
Serial data output pin
7
PROG
EEPROM Programming Enable
Input
8
GND Power supply ground
9
V_REFL Minimum DAC output voltage
10
NC
No Connect
11
NC
No Connect
12
V_OUT2 DPP output channel 2
13
V_OUT1 DPP output channel 1
14
V_REFH Maximum DPP output voltage
DPP addressing is as follows:
DPP OUTPUT
V_OUT1
V_OUT2
A0 A1
00
10
DEVICE OPERATION
The CAT523 is a dual 8-bit configured digitally
programmable potentiometer (DPP) whose outputs
can be programmed to any one of 256 individual
voltage steps. Once programmed, these output
settings are retained in non-volatile memory and will
not be lost when power is removed from the chip.
Upon power up the DPPs return to the settings stored
in non-volatile memory. Each DPP can be written to
and read from independently without effecting the
output voltage during the read or write cycle. Each
output can also be temporarily adjusted without
changing the stored output setting, which is useful for
testing new output settings before storing them in
memory.
DIGITAL INTERFACE
The CAT523 employs a 3 wire, Microwire-like, serial
control interface consisting of Clock (CLK), Chip
Select (CS) and Data In (DI) inputs. For all ope–
rations, address and data are shifted in LSB first. In
addition, all digital data must be preceded by a logic
“1” as a start bit. The DPP address and data are
clocked into the DI pin on the clock’s rising edge.
When sending multiple blocks of information a
minimum of two clock cycles is required between the
last block sent and the next start bit.
Multiple devices may share a common input data line
by selectively activating the CS control of the desired
IC. Data Outputs (DO) can also share a common line
because the DO pin is Tri-Stated and returns to a high
impedance when not in use.
CHIP SELECT
Chip Select (CS) enables and disables the CAT523’s
read and write operations. When CS is high data may
be read to or from the chip, and the Data Output (DO)
pin is active. Data loaded into the DPP control
registers will remain in effect until CS goes low.
Bringing CS to a logic low returns all DPP outputs to
the settings stored in non-volatile memory and
switches DO to its high impedance Tri-State mode.
Because CS functions like a reset the CS pin has
been equipped with a 30 ns to 90 ns filter circuit to
prevent noise spikes from causing unwanted resets
and the loss of volatile data.
CLOCK
The CAT523’s clock controls both data flow in and out
of the IC and non-volatile memory cell programming.
Serial data is shifted into the DI pin and out of the DO
pin on the clock’s rising edge. While it is not
necessary for the clock to be running between data
transfers, the clock must be operating in order to write
to non-volatile memory, even though the data being
saved may already be resident in the DPP wiper
control register.
Doc. No. MD-2005 Rev. I
6
© 2008 SCILLC. All rights reserved.
Characteristics subject to change without notice