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CAT521 View Datasheet(PDF) - Catalyst Semiconductor => Onsemi

Part Name
Description
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CAT521 Datasheet PDF : 10 Pages
1 2 3 4 5 6 7 8 9 10
PIN DESCRIPTION
Pin Name
Function
1
VDD
Power supply positive
2
CLK
Clock input pin
3
RDY/BSY 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
VREFL
10 NC
Minimum DAC output voltage
No Connect
11 NC
No Connect
12
VOUT
13 NC
DPP output
No Connect
14
VREFH
Maximum DPP 1 output voltage
CAT521
DPP addressing is as follows:
DPP OUTPUT
VOUT
A0 A1
1
0
DEVICE OPERATION
The CAT521 is a single 8-bit configured digitally
programmable potentiometer (DPP™) whose output
can be programmed to any one of 256 individual voltage
steps. Once programmed, the output setting is retained
in non-volatile memory and will not be lost when power
is removed from the chip. Upon power up the DPP
returns to the setting stored in non-volatile memory. The
DPP can be written to and read from without effecting the
output voltage during the read or write cycle. The 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 CAT521 employs a 3 wire, Microwire-like 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
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 CAT521’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 register 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
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 CAT521 clock controls both data flow in and out of
the device 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.
No clock is necessary upon system power-up. The
CAT521 internal power-on reset circuitry loads data
from non-volatile memory to the DPP without using the
external clock.
5
Doc. No. 2003, Rev. F
 

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