PLESSEY SEMICONDUCTORS PLESSEY uze off z2zas13 oooaen3 off Semiconductors [-S)-04-07 LOW COST 6-BIT D-A CONVERTER The ZN436 is a monolithic 6-bit D-A converter containing an R-2R ladder network of diffused resistors with precision bipolar switches. ot]t ta y} +Vee {+5V) FEATURES . 4 2 * we s Lia 12 iT Mi s6-Bit Accuracy , AMALOGUE OUTPUT [] 4 11, o6e M = TTL and 5V CMOS Compatible . veer in []5 yon) ac Ms Single +5V Supply nant . . . ke [J opine Wi sSttling Time 1 microsecond Typical wq7 abn HM Designed for Low-Cost Applications H @ = = Commercial and Military Temperature Ranges ZN436J (DC14) ZN436E (DP14) ORDERING INFORMATION Device type Operating temperature Package Pin connections - top view ZN436E 0C to +70C DP14 ZN436J ~55S to +125C DC14 [ TS eee cm | R-2R LADDER a! ANALOGUE | | | wot | ls SWITCHES | VREF o> +] INPUT | | Ltn te deb bb (LSB) DBp DBy DB2 DBg O84 DBs (MSB) 198 Fig.1 System diagram PLESSEY SEMICONDUCTORS INTRODUCTION ; The ZN436 is an 6-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 ladder network results in uze of 2220513 oooaeyy aff zNa96 T-51-09-07 full 6-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. 2. R(Wkn) R |er 2R 2R VREF R R PIN 4 ANALOGUE OUTPUT 0 VOLTS, i} SWICHES INPUT f U [. y L. <_ VOLTAGE __ DBO OBI Fig. 2 The R-2R ladder network DB4 DBS MSB Each 2R element is connected either to OV or Varer 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 22 Suggested external reference sources are the ZN404 or one of the ZN458 range. Each ZN404 is capable of supplying up to five ZN436 circuits and this is increased to ten for the ZN458 range. 199 2N436 PLESSEY SEMICONDUCTORS AcE off 7220513 O008e4S uff ABSOLUTE MAXIMUM RATINGS T-51-09-07 Supply voltage Vcc ee ee ee ee ee (TLV Max. voltage, logic and Vacge inputs .. .. .. +5.5V Storage temperature range .. .. .. .. .. 55to +125C CHARACTERISTICS (at Tamp = 25C and Vcc = +5V unless otherwise specified) Parameter Symbol] Min. | Typ. | Max. | Units Conditions Accuracy (useful resolution) ZN436J 6 - - bits Vacr input = 2.0 to 3.0V ZN436E 6 - - bits Non-linearity - - +0.5} L.S.B. | Note 1 Differential non-linearity - +0.5 - L.S.B. | Note 2 Settling time to 0.5 L.S.B. - 1.0 - ps 1 L.S.B. step Settling time to 0.5 L.S.B. - 2.0 - ys All bits ON to OFF or OFF to ON Offset voltage ZN436J Vos - 5.0 8.0 mV All bits OFF note 1 ZN436E - 3.0 5.0 mV Vos temperature coefficient - 5.0 - pVIPC Full-scale output 2.510} 2.520 | 2.530 Vv All bits ON Ext. Vacr = 2.560V Full-scale temp. coefficient - 3.0 - ppm/C| Ext. Vacs = 2.560V Non-linearity temp. coefficient - 7.5 - ppm/C | Relative to F.S.R. Notes: 1. The ZN436J differs from the ZN436E in the following respects: (a) For the ZN436J, the maximum linearity error may increase to + 1LSB over the temperature ranges - 55 to OC and +70 to +125C. (b) Offset voltage. The difference is due to package lead resistance. This offset will normally "be removed by the setting up procedure, and because the offset temperature coefficient is low, the specified accuracy will be maintained. 2. Monotonic over the full operating temperature range. PLESSEY SEMICONDUCTORS L2E off 7220513 0008246 bff ZN436 CHARACTERISTICS (cont.) T-51-09-07 Parameter Symbol |Min.| Typ. | Max. | Units Conditions Analogue output resistance Ro - 10 - kQ External reference voltage 0 - 3.0 Vv Supply voltage Vec 4.5] - 5.5 Vv Supply current Ig - 5 9 mA High level input voltage Vin 2.0] - - V Low level input voltage Vie 7 - 0.7 Vv High level input current Vin - - 10 BA Vec=max., Vj=2.4V - - 100 pA Vec=max., V)=5.5V Low level input current hie - - |-0.18] mA | Vec=max., Vj) =0.3V APPLICATIONS 1. 6-bit D-A converter The ZN436 gives an analogue voltage output directly from pin 4 therefore the usual current to voltage converting amplifier is not required. The output voltage drift, due to the temperature coefficient of the analogue output resistance Ro, will be less than 0.004% per C (or 12SB/100C) if R, is chosen to be 2650k0. in order to remove the offset voltage and to calibrate the converter a buffer amplifier is necessary. Fig. 3 shows a typical scheme. To minimise temperature drift in this and similar applications the source resistance to the inverting input of the operational amplifier should be approximately 6kQ. The calibration procedure is as follows: i. Set all bits to OFF (low) and adjust R, until Vout =0.000V. ii. Set all bits to ON (high) and adjust R, until Vout = Nominal full-scale reading - 1LSB. iii. Repeat i. and ii. 201 znNagg -:PLESSEY SEMICONDUCTORS 1ceE off 7220513 O004C4? aj T-51-09-07 +5Vo oor 68a Net 0B341 14) DB2 ag 2 13} DB2 OBI 13 12)- DBI ANALOGUE 4 11} 080 OUTPUT VREF INO 5 10]NC. 68k (2-5V NOMINAL) ncJ6 9INC. Ri SET 7 BINC Ska FSR 18ka a OV an 6-5V Fig. 3 6-bit D-A converter Alternative output buffer using the 741 operational amplifier, may be used as the out- The following circuit, employing the 741 put buffer (Fig. 3). ZN 436 Ping Fig.4 The 741 as output buffer 202