MAY 1994
DS3021-2.2
ZN426E8
8-BIT D-A CONVERTER
The ZN426 is a monolithic 8-bit D-A converter
containing an R-2R ladder network of diffused resistors with
precision bipolar switches, and a 2.5V precision voltage
reference. BIT 3 1 14 V CC (+5V)
BIT 2 2 13 BIT 4
FEATURES (MSB) BIT 1 3 12 BIT 5
1/2 LSB Linearity Error ANALOG OUTPUT 4 ZN426E8 11 BIT 6
V REF IN 5 10 BIT 7
Guaranteed Monolithic over the Full Operating V REF OUT 6 9 BIT 8 (LSB)
Temperature Range 0V 7 NC
8
0C to +70C
TTL and 5V CMOS Compatible
Single 5V Supply
Settling Time 1 microsecond Typical DP14
Only Reference Capacitor and Resistor Required
ABSOLUTE MAXIMUM RATINGS
Supply voltage +7.0V Fig.1 Pin connections (not to scale) - top view
Max.voltage, logic and VREF inputs+5.5V
Operating temperature range0C to +70C
Storage temperature range-55C to +125C
ORDERING INFORMATION
Ambient operating temperature 0C to +70C
Package, ZN426E8DP14
Fig.2 System diagram
ZN426
ELECTRICAL CHARACTERISTICS
(at Tamb = 25C and VCC = +5V unless otherwise specified)
Parameter Symbol Units Conditions
Min. Typ. Max.
Converter
Resolution 8 - - bits
Non-linearity - - 0.5 LSB
Differential non-linearity - 0.5 - LSB Note 1
Settling time to 0.5LSB - 1.0 - s 1LSB step
Settling time to 0.5LSB - 2.0 - s All bits ON to OFF
or OFF to ON
Offset voltage ZN426E8 and D VOS - 3.0 5.0 mV All bits OFF
VOS temperature coefficient - 5 - V/C
Full-scale output 2.545 2.550 2.555 V All bits ON
Ext. VREF = 2.560V
Full-scale temp. coefficient - 3 - ppm/C Ext. VREF = 2.560V
Non-linearity temp. coefficient - 7.5 - ppm/C Relative to F.S.R.
Analog output resistance RO - 10 - k
External reference voltage 0 - 3.0 V
Supply voltage VCC 4.5 - 5.5 V
Supply current IS - 5 9 mA
High level input voltage VIH 2.0 - - V
Low level input voltage VIL - - 0.7 V
High level input current IIH - - 10 A VCC = max.
VI = 2.4V
- - 100 A VCC = max.
VI = 5.5V
Low level input current IIL - - -0.18 mA VCC = max.
VI = 0.3V
Internal voltage reference
Output voltage VREF 2.475 2.55 2.626 V Note 2 RREF = 390
Slope resistance RS - 1 2 RREF = 390
VREF temperature coefficient - 40 - ppm/C RREF = 390
NOTE 1: Monotonic over full temperature range.
NOTE 2:The internal reference requires a 1F stabilising capacitor between VREF OUT and 0V and a 390 resistor, RREF,
between VCC and VREF OUT.
INTRODUCTION
The ZN426 is an 8-bit D-A converter. It contains an The use of on-chip voltage reference is pin optional to
advanced design of R-2R ladder network and an array of retain flexibility. An external fixed or varying reference may
precision bipolar switches plus a 2.5V precision voltage therefore be substituted. In this case there is no need to
reference on a single monolithic chip. supply power to the internal reference so RREF and CREF
The special design of the ladder network results in full can be omitted.
8-bit accuracy using normal defused resistors.
2
ZN426
The converter is of the voltage switching type and uses Binary weighted voltages are produced at the output of
an R-2R resistor ladder network as shown in Fig.3. the R-2R ladder, the value depending on the digital number
applied to the bit inputs.
Each 2R element is connected either to 0V or VREF by
transistor switches specially designed for low offset voltage
(typically 1mV).
Fig.3 The R-2R ladder network
APPLICATIONS
8-bit D-A Converter
The ZN426 gives an analog voltage output directly from i. Set all bits to OFF (low) and adjust R2 until
pin 4 therefore the usual current to voltage converting VOUT = 0.000V.
amplifier is not required. The output voltage drift, due to the
temperature coefficient of the analog output resistance RO, ii. Set all bits to ON (high) and adjust R1 until
will be less than 0.004% per C (or 1LSB/100C) if RL is VOUT = Normal full-scale reading - 1LSB
chosen to be 650k.
In order to remove the offset voltage and to calibrate the iii. Repeat i. and ii.
converter a buffer amplifier is necessary. Fig.4 shows a e.g. Set F.S.R. to + 3.840V - 1LSB
typical scheme using the internal reference voltage. To =3.825V
minimise temperature drift in this and similar applications the
source resistance to the inverting input of the operational (1LSB = 3.84 =15.0mV)
256
amplifier should be approximately 6k. The calibration
procedure is as follows:
Fig.4 8-bit D-A converter
3
ZN426
Alternative Output Buffer Using the 741
The circuit of Fig.5, employing the 741 operational
amplifier, may be used as the output buffer.
Fig.5 The ZLD741 as output buffer
HEADQUARTERS OPERATIONS CUSTOMER SERVICE CENTRES
GEC PLESSEY SEMICONDUCTORS FRANCE & BENELUX Les Ulis Cedex Tel: (1) 64 46 23 45 Fax: (1) 64 46 06 07
Cheney Manor, Swindon, GERMANY Munich Tel: (089) 3609 06-0 Fax: (089) 3609 06-55
Wiltshire, United Kingdom. SN2 2QW ITALY Milan Tel: (02) 66040867 Fax: (02)66040993
Tel: (01793) 518000 JAPAN Tokyo Tel: (03) 5276-5501 Fax: (03) 5276-5510
Fax: (01793) 518411 NORTH AMERICA Scotts Valley, USA Tel: (408) 438 2900 Fax: (408) 438 7023
SOUTH EAST ASIA Singapore Tel: (65) 3827708 Fax: (65) 3828872
GEC PLESSEY SEMICONDUCTORS SWEDEN Stockholm Tel: 46 8 702 97 70 Fax: 46 8 640 47 36
P.O. Box 660017, TAIWAN, ROC Taipei Tel: 886 2 5461260 Fax: 886 2 7190260
1500 Green Hills Road, UK, EIRE, DENMARK, FINLAND & NORWAY
Scotts Valley, California 95067-0017, Swindon Tel: (01793) 518510 Fax: (01793) 518582
United States of America. These are supported by Agents and Distributors in major countries world-wide.
Tel (408) 438 2900 GEC Plessey Semiconductors 1994 Publication No. DS3021 Issue No. 2.2 May 1994
Fax: (408) 438 5576 TECHNICAL DOCUMENTATION - NOT FOR RESALE. PRINTED IN UNITED KINGDOM
This publication is issued to provide information only which (unless agreed by the Company in writing) may not be used, applied or reproduced for any purpose nor form part of any order or contract nor to be
regarded as a representation relating to the products or services concerned. No warranty or guarantee express or implied is made regarding the capability, performance or suitability of any product or service. The
Company reserves the right to alter without prior knowledge the specification, design or price of any product or service. Information concerning possible methods of use is provided as a guide only and does not
constitute any guarantee that such methods of use will be satisfactory in a specific piece of equipment. It is the user's responsibility to fully determine the performance and suitability of any equipment using such
4 information and to ensure that any publication or data used is up to date and has not been superseded. These products are not suitable for use in any medical products whose failure to perform may result in
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