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PURPOSES ONLY AND IS NOT
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ZN428E8/ZN428J8/ZN428D
8-BIT LATCHED INPUT D-A CONVERTER
AUGUST 1994
DS3007-2.1
The ZN428 is a monolithic 8-bit D-A converter with input
latches to facilitate updating from a data bus. The latch is
transparent when enable is LOW and the data is held when
enable is taken HIGH. The ZN428 also contains a 2.5V
reference the use of which is pin optional to retain flexibility.
An external fixed or varying reference may therefore be
substituted.
FEATURES
s Contains DAC with Data Latch and On-Chip
Reference
s Guaranteed Monotonic over the Full Operating
Temperature Range
s Single +5V Supply
s Microprocessor Compatible
s TTL and 5V CMOS Compatible
s 800ns Settling Time
s Complementary to ZN427 A to D Series
s Commercial or Military Temperature Range
ORDERING INFORMATION
Device Type
ZN428D
ZN428E8
ZN428J8
Operating temperature
0°C to +70°C
0°C to +70°C
-55°C to +125°C
Package
MP16W
DP16
DC16
BIT 7
BIT 8
NC
ENABLE
ANALOG OUTPUT
VREF IN
VREF OUT
ANALOG GROUND
1 16
2 15
3 14
4 ZN428J8 13
5 ZN428E8 12
6 11
7 10
89
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1 (MSB)
+VCC (+5V)
DIGITAL GROUND
DC16
DP16
BIT 7
BIT 8
NC
ENABLE
ANALOG OUTPUT
VREF IN
VREF OUT
ANALOG GROUND
1 16
2 15
3 14
4 13
5
ZN428D
12
6 11
7 10
89
BIT 6
BIT 5
BIT 4
BIT 3
BIT 2
BIT 1 (MSB)
+VCC (+5V)
DIGITAL GROUND
MP16 WIDE BODY
Fig.1 Pin connections (not to scale) - top view

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ZN428
ABSOLUTE MAXIMUM RATINGS
Supply voltage VCC
Max.voltage, logic and VREF inputs
Operating temperature range
Storage temperature range
Analog ground to digital ground
+7.0V
+VCC
0°C to +70°C (ZN428E8, ZN428D)
-55°C to +125°C (ZN428J8)
-55°C to +125°C
±200mV
ELECTRICAL CHARACTERISTICS
(VCC = +5V, Tamb = 25°C unless otherwise specified)
Parameter
Internal Voltage Reference
Output voltage
Slope resistance
VREF OUT T.C.
Reference current
D-A Converter
Linearity error
Differential non-linearity
Linearity error T.C.
Differential non-linearity T.C.
Offset voltage
Offset voltage T.C.
Full-scale output
Full-scale output T.C.
Analog output resistance
External reference voltage
Settling time to 0.5 LSB
Min.
2.475
-
-
4
-
-
-
-
-
-
2.545
-
-
0
-
-
Typ.
2.550
0.5
50
-
-
±0.5
±3
±6
2
±6
2.550
2
4
-
800
1.25
Max.
2.625
2
-
15
±0.5
-
-
-
5
-
2.555
-
-
3.0
-
-
Operating temperature range:
ZN428D and ZN428 E8
0
- 70
ZN428J8
-55
-
125
Supply voltage (VCC)
Supply current
4.5 5.0 5.5
- 20 30
Power consumption
- 100 -
Note 1: See REFERENCE
Note 2: RL = 10M, CL = 10pF
Note 3: All inputs HIGH (VIH = 3.5V)
Units
V
ppm/°C
mA
LSB
LSB
ppm/°C
ppm/°C
mV
µV/°C
ppm/°C
k
V
ns
µs
°C
°C
V
mA
mW
Conditions
RREF = 390
CREF = 1µF
Note 1
2.0V VREF IN 3.0V
All bits off
External reference
VREF IN = 2.560V,
all bits ON
1 LSB major transition
(Note 2)
All bits ON to OFF or
OFF to ON (Note 2)
Note 3

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ZN428
ELECTRICAL CHARACTERISTICS (cont.)
Parameter
Min.
Logic (over specified operating
temperature range)
High level input voltage
2.0
Low level input voltage
-
High level input current
-
-
Low level input current
-
Input clamp diode voltage
-
Enable pulse width
100
Data set-up time
150
Data hold time
10
Note 4: Set up time before ENABLE goes high
Note 5: Hold time after ENABLE goes high
Typ.
-
-
-
-
-
-1.5
-
-
-
Max.
-
0.8
60
20
-5
-
-
-
-
Units
Conditions
V
V
µA VIN = 5.5V, VCC = Max.
µA VIN = 2.4V, VCC = Max.
µA VIN = 0.4V, VCC = Max.
V IIN = -8mA
ns
ns Note 4
ns Note 5
D-A CONVERTER
The converter is of the voltage switching type and uses
an R-2R ladder network as shown in Fig.3. Each 2R element
is connected to 0V or VREF IN by transistor voltage switches
specially designed for low offset voltage (<1mV). A binary
weighted voltage is produced at the output of the R-2R
ladder.
Fig.3 The R-2R ladder network
Analog
output
=
n
256
(VREF
IN
-
VOS)
+
VOS
where n is the digital input to the D-A from the data latch.
VOS is a small offset voltage produced by the D-A switch
currents flowing through the package lead resistance. The
value of VOS is typically 1mV. This offset will normally be
removed by the setting up procedure (see Operating Notes)
and because the offset temperature coefficient is low
(±6µV/°C)the effect on accuracy is negligible.

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ZN428
Fig.4 Analog output equivalent circuit
Fig.4 shows equivalent circuit of the output (ignoring
VOS). The output resistance R has a temperature coefficient
of +0.2% per °C.
The gain drift due to this is 0.2R % per °C.
R+RL
RL should be chosen as large as possible to make the
gain drift small. As an example if RL = 400kthen the gain
drift due to the T.C. of R for a 100°C change in ambient
temperature will be less than 0.2%. Alternatively the ZN428
can be buffered by an amplifier (see Operating Notes).
REFERENCE
(a) Internal Reference
The internal reference is an active bandgap circuit which
is equivalent to a 2.5V Zener diode with very low slope
impedance (Fig.5). A resistor (RREF), should be connected
between +VCC (pin 10) and pin 7. The recommended value
of 390will supply a nominal reference current of (5.0-
2.5)/0.39 = 6.4mA. A stabilising/decoupling capacitor CREF =
1µF is required between pins 7 and 8 for internal reference
option, VREF OUT (pin 7) being connected to VREF IN (pin 6).
Fig.5 Internal voltage reference