Page 1
1
DO
PROG
RDY/BSY
CLK
1
2
3
4
5
6
7
14
13
12
11
8
10
9
VDD
V
REF
H1
GND
V
OUT
1
CS
DI
V
REF
L1
NC
NC
NC
DO
PROG
RDY/BSY
CLK
1
2
3
4
5
6
7
14
13
12
11
8
10
9
VDD
V
REF
H1
GND
V
OUT
1
CS
DI
V
REF
L1
NC
NC
NC
CAT521
8-Bit Digital POT With Independent Reference Inputs
FEATURES
■ Buffered Outputs
■ Output settings retained without power
■ Output range includes both supply rails
■ Programming voltage generated on-chip
■ Serial µP interface
■ Single supply operation: 2.7V-5.5V
APPLICATIONS
■ Automated product calibration.
■ Remote control adjustment of equipment
■ Offset, gain and zero adjustments in Self-
Calibrating and Adaptive Control systems.
■ Tamper-proof calibrations.
DESCRIPTION
The CAT521 is a dual 8-Bit Memory DAC designed as an
electronic replacement for mechanical potentiometers
and trim pots. Intended for final calibration of products
such as camcorders, fax machines and cellular telephones on automated high volume production lines and
systems capable of self calibration, it is also well suited
for applications were equipment requiring periodic adjustment is either difficult to access or located in a
hazardous environment.
The CAT521 consists of a programmable DAC with
independent high and low reference inputs and is capable of a rail to rail output swing. The output is buffered
by a rail to rail OP AMP. Output settings, stored in nonvolatile EEPROM memory, are not lost when the device
is powered down and are automatically reinstated when
power is returned. The output can be dithered to test
new output values without effecting the stored settings
FUNCTIONAL DIAGRAM PIN CONFIGURATION
and stored settings can be read back without disturbing
the DAC’s output.
Control of the CAT521 is accomplished with a simple 3
wire serial interface. A Chip Select pin allows several
CAT521's to share a common serial interface and communications back to the host controller is via a single
serial data line thanks to the CAT521’s Tri-Stated Data
Output pin. A RDY/BSY output working in concert with
an internal low voltage detector signals proper operation
of EEPROM Erase/Write cycle.
The CAT521 operates from a single 3–5 volt power
supply. The high voltage required for EEPROM Erase/
Write operations is generated on-chip.
The CAT521 is available in the 0°C to 70°C Commercial
and –40°C to +85°C Industrial operating temperature
ranges and offered in 14-pin plastic DIP and Surface
mount packages.
DIP Package (P)
SOIC Package (J)
CAT521
© 2001 by Catalyst Semiconductor, Inc.
Characteristics subject to change without notice
Advanced Information
CAT521
CAT521
GND
EEPROM
LATCH
DAC 1
12
PROG
RDY/BSY
PROGRAM
CONTROL
H.V.
CHARGE
PUMP
SERIAL DATA OUTPUT
V
1
OUT
V L1
REF
V H1
REF
DO
V
DD
DATA
CONTROLLER
14
3
CLK
CS
2
4
5
7
9
8
1
6
DI
+
–
Page 2
CAT521
2
Advanced Information
ABSOLUTE MAXIMUM RATINGS
Supply Voltage*
V
DD
to GND ......................................–0.5V to +7V
Inputs
CLK to GND............................–0.5V to V
DD
+0.5V
CS to GND..............................–0.5V to V
DD
+0.5V
DI to GND ...............................–0.5V to V
DD
+0.5V
RDY/BSY to GND...................–0.5V to V
DD
+0.5V
PROG to GND ........................–0.5V to V
DD
+0.5V
V
REF
H to GND ........................–0.5V to V
DD
+0.5V
V
REF
L to GND.........................–0.5V to V
DD
+0.5V
Outputs
D0 to GND...............................–0.5V to V
DD
+0.5V
V
OUT
1– 2 to GND...................–0.5V to V
DD
+0.5V
Operating Ambient Temperature
Commercial (‘C’ suffix) .................... 0°C to +70°C
Industrial (‘I’ suffix)...................... – 40°C to +85°C
Junction Temperature ..................................... +150°C
Storage Temperature ....................... –65°C to +150°C
Lead Soldering (10 sec max) .......................... +300°C
* Stresses above those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Absolute
Maximum Ratings are limited values applied individually while
other parameters are within specified operating conditions,
and functional operation at any of these conditions is NOT
implied. Device performance and reliability may be impaired by
exposure to absolute rating conditions for extended periods of
time.
DC ELECTRICAL CHARACTERISTICS: V
DD
= +2.7V to +5.5V, V
REF
H = VDD, V
REF
L = 0V, unless otherwise specified
RELIABILITY CHARACTERISTICS
Symbol Parameter Min Max Units Test Method
V
ZAP
(1)
ESD Susceptibility 2000 Volts MIL-STD-883, Test Method 3015
I
LTH
(1)(2)
Latch-Up 100 mA JEDEC Standard 17
NOTES: 1. This parameter is tested initially and after a design or process change that affects the parameter.
2. Latch-up protection is provided for stresses up to 100mA on address and data pins from –1V to VCC + 1V.
Symbol Parameter Conditions Min Typ Max Units
Resolution 8 — — Bits
Accuracy
INL Integral Linearity Error I
LOAD
= 10 µA, TR = C — 0.6 ± 1 LSB
TR = I — 0.6 ± 1 LSB
I
LOAD
= 40 µA, TR = C — 1.2 — LSB
TR = I — 1.2 — LSB
DNL Differential Linearity Error I
LOAD
= 10 µA, TR = C — 0.25 ± 0.5 LSB
TR = I — 0.25 ± 0.5 LSB
I
LOAD
= 40 µA, TR = C — 0.5 — LSB
TR = I — 0.5 — LSB
Logic Inputs
I
IH
Input Leakage Current VIN = V
DD
——10µA
I
IL
Input Leakage Current VIN = 0V — — –10 µA
V
IH
High Level Input Voltage 2 — V
DD
V
V
IL
Low Level Input Voltage 0 — 0.8 V
V
RH
V
REF
H Input Voltage Range 2.7 — V
DD
V
V
RL
V
REF
L Input Voltage Range GND — VDD -2.7 V
Z
IN
V
REF
H–V
REF
L Resistance — 28K — Ω
V
OH
High Level Output Voltage IOH = – 40 µAV
DD
–0.3 — — V
V
OL
Low Level Output Voltage IOL = 1 mA, VDD = +5V — — 0.4 V
IOL = 0.4 mA, VDD = +3V — — 0.4 V
Logic Outputs
References
Page 3
CAT521
3
Advanced Information
DC ELECTRICAL CHARACTERISTICS (Cont.):
VDD = +2.7V to +5.5V, V
REF
H = VDD, V
REF
L = 0V, unless otherwise specified
Symbol Parameter Conditions Min Typ Max Units
Symbol Parameter Conditions Min Typ Max Units
Digital
t
CSMIN
Minimum CS Low Time 150 — — ns
t
CSS
CS Setup Time 100 — — ns
t
CSH
CS Hold Time 0 — — ns
t
DIS
DI Setup Time 50 — — ns
t
DIH
DI Hold Time 50 — — ns
t
DO1
Output Delay to 1 — — 150 ns
t
DO0
Output Delay to 0 — — 150 ns
t
HZ
Output Delay to High-Z — 400 — ns
t
LZ
Output Delay to Low-Z — 400 — ns
t
BUSY
Erase/Write Cycle Time — 4 5 ms
t
PS
PROG Setup Time 150 — — ns
t
PROG
Minimum Pulse Width 700 — — ns
t
CLK
H Minimum CLK High Time 500 — — ns
t
CLK
L Minimum CLK Low Time 300 — — ns
f
C
Clock Frequency DC — 1 MHz
Analog
t
DS
DAC Settling Time to 1 LSB C
LOAD
= 10 pF, VDD = +5V — 3 10 µs
C
LOAD
= 10 pF, VDD = +3V — 6 10 µs
Pin Capacitance
C
IN
Input Capacitance VIN = 0V, f = 1 MHz
(2)
—8—pF
C
OUT
Output Capacitance V
OUT
= 0V, f = 1 MHz
(2)
—6—pF
NOTES: 1. All timing measurements are defined at the point of signal crossing VDD / 2.
2. These parameters are periodically sampled and are not 100% tested.
CL = 100 pF,
see note 1
AC ELECTRICAL CHARACTERISTICS:
VDD = +2.7V to +5.5V, V
REF
H = VDD, V
REF
L = 0V, unless otherwise specified
Analog Output
FSO Full-Scale Output Voltage VR = V
REF
H – V
REF
L 0.99 VR0.995 V
R
—V
ZSO Zero-Scale Output Voltage VR = V
REF
H – V
REF
L — 0.005 VR0.01 V
R
V
I
L
DAC Output Load Current — — 1 µA
R
OUT
DAC Output Impedance VDD = V
REF
H = +5V — — 1K Ω
VDD = V
REF
H = +3V — — 1K Ω
PSSR Power Supply Rejection I
LOAD
= 1 µA — — 1 LSB / V
Temperature
TC
O
V
OUT
Temperature Coefficient VDD = +5V, I
LOAD
= 250nA — — 200 µV/ °C
V
REF
H= +5V, V
REF
L = 0V
TC
REF
Temperature Coefficient of V
REF
H to V
REF
L — 700 — ppm / °C
V
REF
Resistance
Power Supply
I
DD1
Supply Current (Read) Normal Operating — 0.4 0.6 mA
I
DD2
Supply Current (Write) Programming, VDD = 5V — 1.6 2.5 mA
VDD = 3V — 1.0 1.6 mA
V
DD
Operating Voltage Range 2.7 — 5.5 V
Page 4
CAT521
4
Advanced Information
t
o
1 2 3 4 5
CLK
CS
DI
DO
PROG
t H
CLK
t L
CLK
t
CSH
t
CSS
t
CSMIN
t
DIS
t
DIH
t
DO0
t
LZ
t
DO1
t
HZ
RDY/BSY
t
PROG
t
PS
t
o
1 2 3 4 5
t
BUSY
A. C. TIMING DIAGRAM
Page 5
CAT521
5
Advanced Information
PIN DESCRIPTION
Pin Name Function
1V
DD
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
9V
REF
L1 Minimum DAC 1 output voltage
10 NC No Connect
11 NC No Connect
12 V
OUT
1 DAC 1 output
13 NC No Connect
14 V
REF
H1 Maximum DAC 1 output voltage
DEVICE OPERATION
The CAT521 is a single 8-bit Digital to Analog Converter
(DAC) whose output can be programmed to any one of
256 individual voltage steps. Once programmed, the
output setting is retained in non-volatile EEPROM
memory and will not be lost when power is removed from
the chip. Upon power up the DAC returns to the setting
stored in EEPROM memory. The DAC 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 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.
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 DAC control register 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 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’s clock controls both data flow in and out of
the device 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
CAT521’s internal power-on reset circuitry loads data
from EEPROM to the DAC without using the external
clock.
DAC addressing is as follows:
DAC OUTPUT A0 A1
V
OUT
101
Page 6
CAT521
6
Advanced Information
As data transfers are edge triggered clean clock transitions are necessary to avoid falsely clocking data into the
control register. Standard CMOS and TTL logic families
work well in this regard and it is recommended that any
mechanical switches used for breadboarding or device
evaluation purposes be debounced by a flip-flop or other
suitable debouncing circuit.
V
REF
V
REF
, the voltage applied between pins V
REFH &VREF
L,
sets the DAC’s Zero to Full Scale output range where
V
REF
L = Zero and V
REFH
= Full Scale. V
REF
can span the
full power supply range or just a fraction of it. In typical
applications V
REFH &VREF
L are connected across the
power supply rails. When using less than the full supply
voltage be mindfull of the limits placed on V
REF
H and
V
REF
L as specified in the References section of DC
Electrical Characteristics.
READY/
BUSYBUSY
BUSYBUSY
BUSY
When saving data to non-volatile EEPROM memory, the
Ready/Busy ouput (RDY/BSY) signals the start and
duration of the EEPROM erase/write cycle. Upon receiving a command to store data (PROG goes high) RDY/
BSY goes low and remains low until the programming
cycle is complete. During this time the CAT521 will
ignore any data appearing at DI and no data will be
output on DO.
RDY/BSY is internally ANDed with a low voltage detector circuit monitoring V
DD.
If V
DD
is below the minimum
value required for EEPROM programming, RDY/BSY
will remain high following the program command indicating a failure to record the desired data in non-volatile
memory.
DATA OUTPUT
Data is output serially by the CAT521, LSB first, via the
Data Out (DO) pin following the reception of a start bit
and two address bits by the Data Input (DI). DO
becomes active whenever CS goes high and resumes
its high impedance Tri-State mode when CS returns low.
Tri-Stating the DO pin allows several 521s to share a
single serial data line and simplifies interfacing multiple
521s to a microprocessor.
WRITING TO MEMORY
Programming the CAT521’s EEPROM memory is accomplished through the control signals: Chip Select
(CS) and Program (PROG). With CS high, a start bit
followed by a two bit DAC address and eight data bits are
clocked into the DAC control register via the DI pin. Data
enters on the clock’s rising edge. The DAC output
changes to its new setting on the clock cycle following
D7, the last data bit.
Programming is accomplished by bringing PROG high
sometime after the start bit and at least 150 ns prior to the
rising edge of the clock cycle immediately following the
D7 bit. Two clock cycles after the D7 bit the DAC control
register will be ready to receive the next set of address
and data bits. The clock must be kept running throughout the programming cycle. Internal control circuitry
takes care of generating and ramping up the programming voltage for data transfer to the EEPROM cells. The
CAT521’s EEPROM memory cells will endure over
1,000,000 write cycles and will retain data for a minimum
of 100 years without being refreshed.
READING DATA
Each time data is transferred into the DAC control
register currently held data is shifted out via the D0 pin,
thus in every data transaction a read cycle occurs. Note,
however, that the reading process is destructive. Data
must be removed from the register in order to be read.
Figure 2 depicts a Read Only cycle in which no change
occurs in the DAC’s output. This feature allows µPs to
poll DACs for their current setting without disturbing the
output voltage but it assumes that the setting being read
is also stored in EEPROM so that it can be restored at the
end of the read cycle. In Figure 2 CS returns low before
the 13th clock cycle completes. In doing so the EEPROM’s
Figure 1. Writing to Memory Figure 2. Reading from Memory
A0 A11
DO
DI
CS
PROG
DAC
OUTPUT
t 1 2 3 4 5 6 7 8 9 10 11 12
o
CURRENT
DAC VALUE
NON-VOLATILE
D0 D1 D2 D3 D4 D5 D6 D7
CURRENT DAC DATA
RDY/BSY
D0 D1 D2 D3 D4 D5 D6 D7
A0 A1 D0 D1 D2 D3 D4 D5 D6 D71
NEW DAC DATA
CURRENT DAC DATA
CURRENT
DAC VALUE
NON-VOLATILE
DAC
OUTPUT
PROG
DO
DI
CS
NEW
DAC VALUE
VOLATILE
NEW
DAC VALUE
NON-VOLATILE
t 1 2 3 4 5 6 7 8 9 10 11 12 N N+1 N+2
o
RDY/BSY
Page 7
CAT521
7
Advanced Information
MSB LSB
1111 1111 —— (.98 V ) + .01 V = .990 V V = +4.90V
1000 0000 —— (.98 V ) + .01 V = .502 V V = +0.02V
0111 1111 —— (.98 V ) + .01 V = .498 V V = -0.02V
0000 0001 —— (.98 V ) + .01 V = .014 V V = -4.86V
0000 0000 —— (.98 V ) + .01 V = .010 V V = -4.90V
REF REF REF
IF
V = 5V
REF
255
255
OUT
DAC INPUT DAC OUTPUT ANALOG
R = R
OUTPUT
REF REF REF OUT
128
255
127
255
REF REF REF OUT
1
255 REF REF REF OUT
REF REF REF OUT
0
255
V = 0.99 V
FS REF
V = 0.01 V
ZERO REF
V = ——— (V - V ) + V
DAC
CODE
255
FS
ZERO ZERO
Figure 3. Temporary Change in Output
D0 D1 D2 D3 D4 D5 D6 D7
A0 A1 D0 D1 D2 D3 D4 D5 D6 D71
NEW DAC DATA
CURRENT DAC DATA
DO
DI
CS
PROG
DAC
OUTPUT
t 1 2 3 4 5 6 7 8 9 10 11 12 N N+1 N+2
o
CURRENT
DAC VALUE
NON-VOLATILE
NEW
DAC VALUE
VOLATILE
CURRENT
DAC VALUE
NON-VOLATILE
RDY/BSY
setting is reloaded into the DAC control register. Since
this value is the same as that which had been there
previously no change in the DAC’s output is noticed.
Had the value held in the control register been different
from that stored in EEPROM then
a change would occur
at the read cycle’s conclusion.
TEMPORARILY CHANGE OUTPUT
The CAT521 allows temporary changes in the DAC’s
output to be made without disturbing the settings retained in EEPROM memory. This feature is particularly
useful when testing for a new output setting and allows
for user adjustment of preset or default values without
losing the original factory settings.
Figure 3 shows the control and data signals needed to
effect a temporary output change. DAC settings may be
changed as many times as required. The temporary
setting remains in effect long as CS remains high. When
CS returns low the DAC will return to the output value
stored in EEPROM memory.
When it is desired to save a new setting acquired using
this feature, the new value must be reloaded into the
DAC control register prior to programming. This is because the CAT521’s internal control circuitry discards
from the programming register the new data two clock
cycles after receiving it if no PROG signal is received.
Amplified DAC Output
APPLICATION CIRCUITS
Bipolar DAC Output
OPT 505
GND
V
DD
V H
REF
V L
REF
CONTROL
& DATA
+
–
OP 07
V = ( ) -V
OUT
R
F
R +
I
-15V
+15V
+5V
RR
I
F
R
I
IRF
V
DAC
For R =IR
F
V = 2V -V
OUT IDAC
V
i
V
OUT
CAT521
OPT 505
GND
V
DD
V H
REF
V L
REF
CONTROL
& DATA
+
–
OP 07
V
OUT
-15V
+15V
+5V
RR
I
F
V = (1 + –––) V
OUT DAC
R
F
R
I
CAT521
Page 8
CAT521
8
Advanced Information
APPLICATION CIRCUITS (Cont.)
OPT 505
LT 1029
I > 2 mA
V+
GND
V
DD
V = 5.000V
REF
V H
REF
V L
REF
CONTROL
& DATA
OPT 505
GND
V
DD
V H
REF
V L
REF
CONTROL
& DATA
+
–
15K
10 µF
5.1V
10K
4.02 K
1.00K
10 µF
35V
LM 324
1N5231B
MPT3055EL
28 - 32V
OUTPUT
0 - 25V
@ 1A
Digitally Trimmed Voltage Reference Digitally Controlled Voltage Reference
CAT521
CAT521
Page 9
CAT521
9
Advanced Information
ORDERING INFORMATION
Notes:
(1) The device used in the above example is a CAT521JI-TE13 (SOIC, Industrial Temperature, Tape & Reel)
Prefix Device # Suffix
521 J
Product
Number
Package
P: PDIP
J: SOIC
CAT
Optional
Company ID
I
T emperature Range
Blank = Commercial (0˚C to +70˚C)
I = Industrial (-40˚C to +85˚C)
-TE13
Tape & Reel
TE13:
2000/Reel
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