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. FEATURES ■ Linearity Error ±1/2 LSB ■ Single +5V Supply ■ Low Power Consumption 25mW Typical ■ Settling Time 1 Microsecond Typical ■ TTL and 5V CMOS Compatible ■ Designed for Low Cost Applications ABSOLUTE MAXIMUM RATINGS Supply voltage, VCC Max. voltage, logic and VREF inputs Storage temperature range +7.0V +5.5V -55°C to +125°C ORDERING INFORMATION Ambient operating temperature Package, ZN429D Package, ZN429E8 -40°C to +85°C MP14 DP14 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 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 MP14 Fig.1 Pin connections (not to scale) - top view ZN429 ELECTRICAL CHARACTERISTICS (at Tamb = 25°C and VCC = +5V unless otherwise specified) Parameter Symbol Units Conditions Min. Typ. Max. Converter Resolution 8 - - bits Accuracy 8 - - bits Non-linearity - - ±0.5 LSB Differential non-linearity - ±0.5 - LSB Settling time to 0.5LSB - 1.0 - µs 1 LSB step Settling time to 0.5LSB - 2.0 - µs All bits ON to OFF or OFF to ON - 3.0 5.0 mV All bits OFF - 5 - µV/°C 2.545 2.550 2.555 V All bits ON Ext. VREF = 2.56V Full-scale temp. coefficient - 3 - ppm/°C Ext. VREF = 2.560V Non-linearity temp. coefficient - 7.5 - ppm/°C Relative to F.S.R. - 10 - kΩ 0 - 3.0 V Offset voltage ZN429E8, ZN429D VOS VOS temperature coefficient Full-scale output Analog output resistance RO External reference voltage Note 1 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 µA VCC = max. VI = 2.4V - - 100 µA VCC = max. VI = 5.5V - - -0.18 mA VCC = max. VI = 0.3V 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 2Ω. 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 10Ω 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 (10kΩ). The required nominal values of R1 and R2 are given by R1 = 10GkΩ and R2 = 10G/(G-1)kΩ. Using these relationships a table of nominal resistance values for R1 and R2 can be constructed for VREF IN = 2.5V. Output Range G R1 R2 +5V 2 20kΩ 20kΩ +10V 4 40kΩ 13.33kΩ 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 2.5µs 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. UNIPOLAR SETTING UP POINTS Output Range, +FS LSB FS - 1LSB +5V 19.5 mV 4.9805V +10V 39.1mV 9.9609V 1LSB = FS 256 UNIPOLAR LOGIC CODING Input Code (Binary) Analog Output (Nominal Value) 11111111 11111110 11000000 10000001 10000000 01111111 01000000 00000001 00000000 FS - 1LSB FS - 2 LSB 3/ FS 4 1 /2 FS + 1LSB 1 /2 FS 1/ FS - 1LSB 2 1/ FS 4 1LSB 0 (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 10kΩ. The nominal values of R1, R2 and R3 which meet these conditions are given by R1 = 20GkΩ, R2 = 20G/(G-1)kΩ and R3 = 20kΩ. 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 G R1 R2 R3 ±5V 2 40kΩ 40kΩ 20kΩ ±10V 4 80kΩ 26.67kΩ 20kΩ 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 2.5µs typical. ZN429 Fig.6 Bipolar operation - basic circuit BIPOLAR ADJUSTMENT PROCEDURE BIPOLAR LOGIC CODING (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 SETTING UP POINTS Input Range, ± FS LSB -FS +(FS 1LSB) ±5V 39.1 mV -5.0000V +4.9609V ±10V 78.1mV -10.0000V 9.9219V Input Code (Offset Binary) Analog Output (Nominal Value) 11111111 11111110 11000000 10000001 10000000 01111111 01000000 00000001 00000000 +(FS - 1LSB) +(FS - 2 LSB) +1/2 FS + 1LSB 0 -1 LSB -1/2 FS -(FS - 1LSB) -FS 1LSB = 2FS 256 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. © 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