CAT525 CATALYST [Catalyst Semiconductor], CAT525 Datasheet - Page 5

• Manufacturer Part Number: CAT525
• Manufacturer: CATALYST [Catalyst Semiconductor]

PIN DESCRIPTION
DEVICE OPERATION
The CAT525 is a quad 8-bit Digital to Analog Converter
(DAC) whose outputs can be programmed to any one of
256 individual voltage steps. Once programmed, these
output settings are retained in non-volatile EEPROM
memory and will not be lost when power is removed from
the chip. Upon power up the DACs return to the settings
stored in EEPROM memory. Each DAC can be written
to and read from independently without effecting the
output voltage during the read or write cycle. Each
output can also be adjusted without altering the stored
output setting, which is useful for testing new output
settings before storing them in memory.
DIGITAL INTERFACE
The CAT525 employs a standard 3 wire serial control
interface consisting of Clock (CLK), Chip Select (CS)
and Data In (DI) inputs. For all operations, 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 DAC
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.
Pin
10
11
12
13
14
15
16
17
18
19
20
1
2
3
4
5
6
7
8
9
Name
V
V
V
CLK
RDY/BSY
CS
DI
DO
PROG
GND
V
V
V
V
V
V
V
V
V
V
REF
REF
DD
REF
REF
REF
REF
OUT
OUT
OUT
OUT
REF
REF
H2
H1
L1
L2
L3
L4
H4
H3
4
3
2
1
Function
Maximum DAC 2 output voltage
Maximum DAC 1 output voltage
Power supply positive
Clock input pin
Ready/Busy output
Chip select
Serial data input pin
Serial data output pin
EEPROM Programming Enable
Input
Power supply ground
Minimum DAC 1 output voltage
Minimum DAC 2 output voltage
Minimum DAC 3 output voltage
Minimum DAC 4 output voltage
DAC 4 output
DAC 3 output
DAC 2 output
DAC 1 output
Maximum DAC 4 output voltage
Maximum DAC 3 output voltage
5
DAC addressing is as follows:
CHIP SELECT
Chip Select (CS) enables and disables the CAT525’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 DAC control registers will
remain in effect until CS goes low. Bringing CS to a logic
low returns all DAC outputs to the settings stored in
EEPROM memory and switches DO to its high imped-
ance Tri-State mode.
Because CS functions like a reset the CS pin has been
desensitized 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 CAT525’s clock controls both data flow in and out of
the IC and EEPROM 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 EEPROM memory, even
though the data being saved may already be resident in
the DAC control register.
No clock is necessary upon system power-up. The
CAT525’s internal power-on reset circuitry loads data
from EEPROM to the DACs without using the external
clock.
DAC OUTPUT
V
V
V
V
OUT
OUT
OUT
OUT
1
2
3
4
A0
0
1
0
1
Doc. No. 25078-00 4/01 - A M-1
A1
0
0
1
1
CAT525