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THIS DOCUMENT IS FOR MAINTENANCE PURPOSES ONLY AND IS NOT RECOMMENDED FOR NEW DESIGNS
MAY 1994
DS3008-2.0
ZN429E8/ZN429D
LOW COST 8-BIT D-A CONVERTER
The ZN429 is a monolithic 8-bit D-A converter containing an R-2R ladder network of diffused resistors with precision bipolar switches.
BIT 3 BIT 2 (MSB) BIT 1 ANALOG OUTPUT V REF IN NC 0V 1 2 3 4 5 6 7 14 13 12 ZN429E8 11 10 9 8 +V CC (+5V) BIT 4 BIT 5 BIT 6 BIT 7 BIT 8 (LSB) NC
FEATURES s Linearity Error 1/2 LSB s Single +5V Supply s Low Power Consumption 25mW Typical s Settling Time 1 Microsecond Typical s TTL and 5V CMOS Compatible s Designed for Low Cost Applications ABSOLUTE MAXIMUM RATINGS
Supply voltage, VCC Max. voltage, logic and VREF inputs Storage temperature range +7.0V +5.5V -55C to +125C
DP14
NC ANALOG OUTPUT V REF IN GROUND BIT 8 BIT 7 GROUND
1 2 3 4 5 6 7
14 13 12 ZN429D 11 10 9 8
BIT 1 BIT 2 BIT 3 +V CC BIT 4 BIT 5 BIT 6
ORDERING INFORMATION
Ambient operating temperature Package, ZN429D Package, ZN429E8 -40C to +85C MP14 DP14
MP14
Fig.1 Pin connections (not to scale) - top view
ZN429
ELECTRICAL CHARACTERISTICS
(at Tamb = 25C and VCC = +5V unless otherwise specified) Parameter Converter Resolution Accuracy Non-linearity Differential non-linearity Settling time to 0.5LSB Settling time to 0.5LSB Offset voltage ZN429E8, ZN429D VOS temperature coefficient Full-scale output Full-scale temp. coefficient Non-linearity temp. coefficient Analog output resistance External reference voltage Supply voltage Supply current High level input voltage Low level input voltage High level input current VCC IS VIH VIL IIH RO VOS Symbol Min. Typ. Max. Units Conditions
8 8 2.545 0 4.5 2.0 -
0.5 1.0 2.0 3.0 5 2.550 3 7.5 10 5 -
0.5 5.0 2.555 3.0 5.5 9 0.7 10 100 -0.18
bits bits LSB LSB s s mV V/C V ppm/C ppm/C k V V mA V V A A mA VCC = max. VI = 2.4V VCC = max. VI = 5.5V VCC = max. VI = 0.3V All bits ON Ext. VREF = 2.56V Ext. VREF = 2.560V Relative to F.S.R. Note 1 1 LSB step All bits ON to OFF or OFF to ON All bits OFF
Low level input current
IIL
-
NOTE 1: Monotonic over full temperature range.
INTRODUCTION
The ZN429 is an 8-bit D-A converter. It contains an advanced design of R-2R ladder network and an array of precision bipolar switches on a single monolithic chip. The special design of the ladder network results in full 8-bit accuracy using normal diffused resistors. The converter is of the voltage switching type and uses an R-2R resistor ladder network as shown in Fig.3. Each 2R element is connected either to 0V or VREF by transistor switches specially designed for low offset voltage (typically 1mV). Binary weighted voltages are produced at the output of the R-2R ladder, the value depending on the digital number applied to the bit inputs. An external fixed or varying reference is required which should have a slope resistance less than 2. Suggested external reference sources are the ZN404 or one of the ZN458 range. Each ZN404 is capable of supplying up to five ZN429 circuits and this is increased to ten for the ZN458 range.
ZN429
Fig.3 The R-2R ladder network
APPLICATIONS
(1) Unipolar D-A Converter The nominal output range of the ZN429 is 0 to VREF IN through a 10 resistance. Other output ranges can readily be obtained by using an external amplifier. The resulting full-scale range is given by VOUT FS =( 1 + R1 ) VREF IN = G.VREF IN R2 The impedance at the inverting input is R1//R2 and for low drift with temperature this parallel combination should be equal to the ladder resistance (10k). The required nominal values of R1 and R2 are given by R1 = 10Gk and R2 = 10G/(G-1)k. Using these relationships a table of nominal resistance values for R1 and R2 can be constructed for VREF IN = 2.5V. Output Range +5V +10V G 2 4 R1 20k 40k R2 20k 13.33k
For gain setting R1 is adjusted about its nominal value. Practical circuit realisations (including amplifier stabilising components) for +5 and +10V output ranges are given in Fig.5. Settling time for a major transition is 2.5s typical.
Fig.4 Unipolar operation - basic circuit
ZN429
Fig.5 Unipolar operation - component values
UNIPOLAR ADJUSTMENT PROCEDURE
(i) Set all bits to OFF (LOW) and adjust zero until VOUT = 0.0000V. (ii) Set all bits ON (HIGH) and adjust gain until VOUT = FS - 1LSB. (2) Bipolar D-A Converter For bipolar operation the output from the ZN429 is offset by half full-scale by connecting a resistor R3 between VREF IN and the inverting input of the buffer amplifier (Fig.6). When the digital input of the ZN429 is zero the analog output is zero and the amplifier output should be -full-scale. An input of all ones to the D-A will give a ZN429 output of d VREF IN and the amplifier output required is +full-scale. Also, to match the ladder resistance the parallel combination of R1, R2 and R3 should be 10k. The nominal values of R1, R2 and R3 which meet these conditions are given by R1 = 20Gk, R2 = 20G/(G-1)k and R3 = 20k. where the resultant output range is G.VREF IN. Assuming that VREF IN = 2.5V the nominal values of resistors for 5 and 10V output ranges are given in the following table: Output Range 5V 10V G 2 4 R1 40k 80k R2 40k 26.67k R3 20k 20k
UNIPOLAR SETTING UP POINTS
Output Range, +FS +5V +10V
1LSB = FS 256
LSB 19.5 mV 39.1mV
FS - 1LSB 4.9805V 9.9609V
UNIPOLAR LOGIC CODING
Input Code (Binary) 11111111 11111110 11000000 10000001 10000000 01111111 01000000 00000001 00000000 Analog Output (Nominal Value) FS - 1LSB FS - 2 LSB 3/ FS 4 1 /2 FS + 1LSB 1 /2 FS 1/ FS - 1LSB 2 1/ FS 4 1LSB 0
Minus full scale (0FFSET) is set by adjusting R1 about its nominal value relative to R3. Plus full-scale (GAIN) is set by adjusting R2 relative to R1. Settling time for a major transistion is 2.5s typical.
ZN429
Fig.6 Bipolar operation - basic circuit
BIPOLAR ADJUSTMENT PROCEDURE
(i) Set all bits to OFF (LOW) and adjust OFFSETuntil the amplifier output reads -FULL-SCALE. (ii) Set all bits ON (HIGH) and adjust gain until the amplifier reads +(FULL-SCALE - 1LSB).
BIPOLAR LOGIC CODING
Input Code (Offset Binary) 11111111 11111110 11000000 10000001 10000000 01111111 01000000 00000001 00000000 Analog Output (Nominal Value) +(FS - 1LSB) +(FS - 2 LSB) +1/2 FS + 1LSB 0 -1 LSB -1/2 FS -(FS - 1LSB) -FS
BIPOLAR SETTING UP POINTS
Input Range, FS 5V 10V
1LSB = 2FS 256
LSB
-FS
+(FS 1LSB) +4.9609V 9.9219V
39.1 mV 78.1mV
-5.0000V -10.0000V
Fig.7 Bipolar operation - component values
ZN429
HEADQUARTERS OPERATIONS GEC PLESSEY SEMICONDUCTORS Cheney Manor, Swindon, Wiltshire, United Kingdom. SN2 2QW Tel: (01793) 518000 Fax: (01793) 518411 GEC PLESSEY SEMICONDUCTORS P.O. Box 660017, 1500 Green Hills Road, Scotts Valley, California 95067-0017, United States of America. Tel (408) 438 2900 Fax: (408) 438 5576
CUSTOMER SERVICE CENTRES * FRANCE & BENELUX Les Ulis Cedex Tel: (1) 64 46 23 45 Fax: (1) 64 46 06 07 * GERMANY Munich Tel: (089) 3609 06-0 Fax: (089) 3609 06-55 * ITALY Milan Tel: (02) 66040867 Fax: (02)66040993 * JAPAN Tokyo Tel: (03) 5276-5501 Fax: (03) 5276-5510 * NORTH AMERICA Scotts Valley, USA Tel: (408) 438 2900 Fax: (408) 438 7023 * SOUTH EAST ASIA Singapore Tel: (65) 3827708 Fax: (65) 3828872 * SWEDEN Stockholm Tel: 46 8 702 97 70 Fax: 46 8 640 47 36 * TAIWAN, ROC Taipei Tel: 886 2 5461260 Fax: 886 2 7190260 * UK, EIRE, DENMARK, FINLAND & NORWAY Swindon Tel: (01793) 518510 Fax: (01793) 518582 These are supported by Agents and Distributors in major countries world-wide. (c) GEC Plessey Semiconductors 1994 Publication No. DS3008 Issue No. 2.0 May 1994 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

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