ANALOG
DEVICES
HighAccuracy,
l00kHzandlMHz
Voltage
to Frequency
Converte
FEATURES
HighStability: SppmfC max, Model 458L
l5ppmfC max, Model 460L
Low Nonlinearity: 100ppm max, Model 458
150ppm max, Model 460
Versatility: Differential Input Stage
Voltage and Current Inputs
FloatingInputs: t10V CMV
Wide Dynamic Range:6 Decades,Model 460
TTL/DTL CompatibleOueut
tr,uilliililllillillill
&l
APPLICATIONS
Fast Analog-to-DigitalConverter
High ResolutionOptical Data Link
Ratiometric Measurements
2-Wire High Noise lmmunity Digital Transmission
Long Term PrecisionIntegrator
GENERAL DESCRIPTION
Models 458 and 46O are high performance, differential input,
voltage to frequency modular converters designed for analog
to digital applications requiring accuracy and fast data conversion. Model 458 offers a lOOkHz full scale frequency,
guaranteed nonlinearity of 10.017o maximum over five decades (1Hz to l0okHz) of operation and guaranteed low maximum gain drift in three model selections;model 458L:
5ppm/-C max; model 458K: loppm/-C max; and model
458J: 2oppm/-C max. Model 460 offers a lMHz full scale
frequency, guaranteed maximum nonlineariry of 1O.0157o
over six decades (1Hz to lMHz) of operation and guaranteed
low maximum gain drift in three selections; model 46OL:
15ppm/-C max; model 460K: 25ppm/-C max; and model
460J: 50ppm/-C max. Model 460L is the industry's first
lMHz V/F converter to offer 15ppm/oC maximum gain drift.
The differential input stage of models 458 and 460 provide
the versatility of either direct interface to offground 0 to
+1lV input signalswith common mode voltages (CMV) to
110V, as well as ground referenced positive, 0 to +1lV or
negative, 0 to -1lV signals.Both models also accept positive
current signals:0 to +0.5mA, model 458;0 to +1mA, model
460 for cunent to frequency (I/F) applications.
The rated performance of both models 458 and 460 is
achieved without the need for external components or adjustments. Optional adjustments are available for trimming
full scale frequency and the input offset voltage.
l.
I
I
-1w5
wires; in 5/z digit DVM's - featuring high resolution A/D conversion, monotonic performance, no missing codes and high
noise rejection; in strain gage bridge weighing applications accurate ratiometric measurements over wide dynamic range.
DESIGN APPROACH . PRECISION CHARGE BALANCE
Models 458 and 460 incorporate a superior charge balance design that result in high linearity and temperature stability see Figure 1. Both models accept unipolar, single-ended voltage or current input signals directly. By offsetting the input
using the current terminal, models 458 and 46O will accept
bipolar input voltages up to t5V.
OFfSET
VOLTAGE
MOD€L
€
4@
FULL $ALE
1ffiH,
OUPU1
R1
2fr4
tfra
4.7k0
1ftQ
&a
9104
Figure l. Block Diagram - Models 458,460
WHERE TO USE MODELS 458 AND 460
The combination of low gain drift, low nonlinearity and the
versatility of a differential input with both high speed
(lOOkHz/lMHz) models, offer excellent solutions to a wide
variery of demanding applications; in high speed remote data
acquisition systems - two wire data transmission over long
Informationfurnishedby Analog Devicesis believedto be accurate
is assumed
and reliable.However,no responsibility
by AnalogDevices
for its use;nor for any infringements
of patentsor other rightsof third
partieswhich may resultfrom its use.No licenseis grantedby implication or otherwiseunderany patentor patentrightsof AnalogDevices.
P.O. Box 280: Norwood, Massachusetts
02062 U.S.A.
Tel:617132947OO
TWX: 710/394'6577
Telex:924491
Cables:
ANALOGNORWOODMASS
note.d)
otherwis"
Vs=trbvDC
unress
and
@+2b'c
SPECIFICATIINS r,ro,rar
l0okHz
MODEL
J
TRANSFER FUNCTION
Volragelnpur
Current Input
ANALOG INPUT
Configuration
Voltage Signal Range
e^ Teminal (eqgp = 0)
epgp Terminal (e," = 0)
Differential(e^ - e*rr)
Overrange
Current Signal Range (i^)
Common Mode Voltage
Common Mode Rejection
Impedance, e61 Terminal
e*ug Terminal
i61 Terminal
Max Safe lnput
lMHz Full Scale
460
Full Scale
458
J
K
four = (1o4Hzlv) enJ
f6g1 = (2 x 10"H2lmA) i^
four = (losHz/v) eb,l
fouT = (1ooHz/mA) in\,I
Differential
Differential
0 to +10V dc min
O to -10V dc min
0 to +1oV dc min
+ 10% min
o ro +O,smA min
1 10V
40dB
20kQ
0 to +10V dc min
O to -10V dc min
o to +lOV dc min
+1O7omln
O to +1mA min
110V
40dB
1OkQ
20kQ
OQ
40ko
OQ
!vs
ACCURACY
Warm Up Time
N o n l i n e a r i t y ,e h t = + O . 1 m V t o + 1 1 V
elN = -o lmV to -l lV
' . ^
,
.
l
fu[ )cate Error
Gain vs. Temperature (o to +7ooC)
vs. Supply Voltage
vs. Time
.
K
rVs
2 Minute s ta O.O2o/o
1O.0150,6
of Full Scale,max
tO.O15',6of Full Scale
+O.17oto +2o/o,max
150ppm/"C max I t25ppm/'C mu
x25ppm/%
t 10ppm/day
5 Seconds to O.010,6
iO.O1% of Full Scale , max
tO.01'lo of Full Scale
+O.1% to +2o/o, max
r2oppm/"C max ' lloppm/'c
tl5ppm/%
l1oppm/day
max
' t5Ppm/oc mu
110mV mu
t30gV/'C max
lLottv loh
t2opgm{d1y
110mV mu
13otv/oC mu
!Iopv/'k
ttopgm{d11
R L S P O N SL
S e r t l i n gT i m e , t O . O l 0 / 6+ l O V S t e P
0verload Recovery Time
3 Output PulsesPlus 2tls
lOms
2 Output Pulrs Plus 2ps
FREQUENCY OUTPUT"
Waveform
Pulse Width
Rise and Fall Time
Pulse Polarity
"1" (High) Level
Logic
"O" (Low) Level
Logic
Capacitive Loading
Fan Out Loading
lmpedance
TTL/DTL Compatible Pulses
5ps
300ns/50ns
Positive
+2.4V min
+O.4V max
5OOPFmax
1O TTL Loads min
3kQ (High State)
TTL/DTL Compatible Pulses
500ns
60ns/5Ons
Positive
+2.4V min
+O.4V max
2OOPFmu
1O TTL Loads min
t15V dc
t(13 to 18)V dc
(+21, 8)ne
tl5V dc
t(13 to 18)V dc
lnput offrt Voltage2
vs. Temperature (0 to +70oc)
vs. Supply Voltage
vs. Time
_
1-:
ozoojuigh stgl:)
.
_.
powrR
suPPLYa
Voltage, Rated Performance
Voltage, 0perating
Current, Quiescent
TEMPERATURE RANGE
Rated Performance
Operating
Storage
J.2l:,81-t
O to +70oC
-25oc to +85"c
-55'c to +t25oc
O to +7OoC
-25'6 1q +85oC
+tzs"c11lc19
\IECHANICAL
Cse Size
Weight
Mating Socket
rpccrfications
subject to change without
Ac1919
" .
.
AJlusrableto zero using5OOOpotentiometer.
t \Jrus(ableto zero using5OkOpotentiometer.
:Protected for continuous shortrircuits
to gtound and momentary (les the
'Recommcnded power
opply, ADI model 9O4, t15V @ 5OmA output.
z" x2" xo.4"
45 Grams
,
:
2"x2" xo.4"
45 Grams
AC1016
1 ec)
shorE
to the +Vs supply. Output
is not protected
for shorts to th€ -vS $pply.
notice.
OUTLINE DIMENSIONS
l<-
r.o1 (508t MAX---+l
T
Dimensions shown in inches and (mm).
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I O rtN
2 or r5osr MAx---
coMo5
2 oelN.
I
3 O EBEF
o.41
(r.2)
o.04
{1.02)OtA
+vso4
-VsOo
FOUT O 7
TRIMO g
T
BonoM vr&
MATING SOCKET:AC1O16
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Fol
I
,i":i,
II
I
( 2 . 5G
1RID
: !15ppm/"C mex
:.,',.,:,.,"
:,;.l
VOLTAGE TO FREQUENCY OPERATION
Models 458 and 46O provide accurate conversion of analog
signals into a train of constant width and constant amplitude
pulses at a rate directly proportional to the analog signal amplitude. The output continuously tracks the input signal, responding directly to changes in the input signal; external
clock synchronization is not required. The output pulse
rrain is TTL/DTL compatible, permitting direct interface to
digital processing circuits.
BASIC V/F HOOK.UP AND OPTIONAL TRIMS
Models 458 and 46O can be applied directly to achieve rated
performance without external trim potentiometers or other
components. Figures 2, 3 and 4 below illustrate the basic
wiring connections for either V/F converter model. Using the
basic hookup without trims, full scale (e^ = 1OV) accuracy
is +O.1olo1s +2o/oand the input offset voltage is tlomV
max. The full scale and input offset voltage errors can be
eliminated by using the FINE TRIM PROCEDURE'
Set the input voltage to +10.000V and adjust the FULL
SCALE trim for an outPut pulse frequency of lOOkHz (model
458), or lMHz (model +60). The V/F converter may now be
used without further adiustment.
DIFFERENTIAL INPUT
The eng and epBp input terminals represent a true differential input capable of accepting a signal from a strain gage
bridge, a balanced line, or a signal source sitting at a common mode voltage. The differential input eliminates the need
for a differential amplifier to handle these signals'
To apply the 458 or 460 voltage irputs differentially, the
en{ pin must always be positive with respect to the e*u"
pin as shown in Figure 4. The differential signal source may
be completely floating with common mode voltages up to
J1OV max. For differential inputs the outPut frequency is:
/er+ez\
F o u =r f 11.'-.')*\-/.
/
L\-h"-/
FINE TRIM PROCEDURE
Connect the optional trims as shown in Figure 2, 3 or 4 and
allow a five minute warm-up after initial power turn-on.
Using a precision, stable voltage source, set the input voltage,
eg, to 1OmV. Adjust the OFFSET trim, Ro, for an output
pulse interval of O.1 sec (model 458) or O.O1sec (model 46O).
Ke= loauz/V; model 458
'
10"HzlV: model 46o
OFFSETTING INPUT FOR BIPOLAR INPUTS
The input summingterminal, +iil,J,may be used to improve
dynamic responseas well as scalethe output frequency to
directly convert bipolar input voltages.An offset current is
fed through an external resistorfrom a stablevoltage reference.As shown in Figure 5, input voltagesof t5V min can
be converteddirectly.
+15Vm
-.35:iET
-15Vm
MooELs
458,460
7
Four
8
LOAD
RL
ANALOG
COMMON
CMR ERROR
INPUT
SIGNAL
V/F INTERCONNECTIONS
FULL SCALE
ADJUST
t
f - ], ( c r n n/ _KJ t
_
POWER COMMON
Figure 2. Positive lnput Signal
INPUT
| *..1 ",Tr-l
-fei-T-Ere-]
+15Vm
FULL SALE
ADJUST
R
^ OFFSET
..U
ADJUST
-15VDC
MoDELs
1158,il60
ANALOG
COMMON
7
Four
|
458
f
@
I2*Q
l3eA
MODEL €8
OUTPUT
MODEL 4@
OUTPUT
I
0
Figure 5. Offfttting lnpu t to Accept !5V Biqolar lnquts
8
The output may also be scaledup so that low amplitude signals,suchas lV will give full scaleoutput frequency; lOOkHz
model 458 or lMHz model 460. By scalingthe output frequency for low level signals,the step responsewill signifi
cantly improve.As shown in Figure 6 for model 458, the
from 2OOpsbefore
step responsefor a 1 volt input decreases
scaling.
input scaling,to 2oprswith
POWER COMMON
Figure 3. Nqative lnput Signal
Figure 4. Floating lnPut Signal
WITH OPTIONAL
OPERATION,
FORVOLTAGETO FREOUENCY
EXTERNALCONNECTIOilS
ADJUSTMENTS
INPUTOFFSETVOLTAGEANO FULL SCALEFREOUENCY
Rs = ruLL scaLt ADJUSTMENT;mQ (us lw T.c. kM,
<50Fn/'c or quivalmt)
Ro = INPUTOFFSETADJUSTMENT;ffio (u$ ld T.c. cerm€t, <soppn/'C o' qui€lont)
CAUTION:DO NOT SHORTOUTPUTTERMINALTO -15V
Figure 6. Off*tting lnput to Achieve lmproved Dynamic
Responrefor Small Signal lnputs
-3-
PERFORMANCESPECIFICATIONS
Nonlinearity: Nonlinearity error is specifiedas a % of 1OV
full scaleinput and is guaranteedover rhe 0.lmV to 1lV
operatingsignalrange;i0.01% max, models458IlKlL,
10.0157omax, models46OJ/K/L.Typical nonlinearityperformance is illustrated in Fizure 7.
0 0r5
- +12v
f-.1
l L 0 v
CMOS/HNIL
OUT
M O O E L S4 6 O J / K / L
M O D E L S4 5 8 J / K / I
=z
Fisure 7. ror,,ro)*'
i)orr' r"116 tnput vottase
Gain Temperature Stability' Gain drift is specified in ppm
of output signal and is guaranteed for Sach model over the
o to +70"C remqerarure range; 5ppm/"c (+5sL), lOppm/'C
(458K), 2Oppm/-C (458J), 15ppm/-C (460L), 25ppml"C
(460K) and 50ppm/oC (460J) max.
LONG TERM PRECISION INTEGRATOR
In critical measurement applications, such as pollution monitoring where it is required to integrate for periods grearer
than t hour with overall accuracy of 0.057o, the V/F converter offers a superior low cost approach when compared to
the traditional operarional integrator circuit. As shown in
Figure 8, the analog signal is applied to a precision input
amplifier, model 52K and then to the ViF input. The V/F
output is connected to a large capacity counter and display,
operating as a totalizer. The total pulse count is equal to the
time integral of the analog input signal. Since the ourput
displayed is an accumulated pulse count, there is no inregrator drift error. A feature of this approach is the infinite
hold capability without errors due to rime drift, since the
counter may be held at any time without affecting the output reading.
NUMB€ROF PULSES
PAOPORTIONAL TO INPUI
t0 To
RESET
INPUT
e
@
rvr
@
l:J
@
L:J
HUNOREDS
TENS
UNITS
C O U N T € R SA N D O I S P L A Y R € A O O U T _ T I L 3 6 1 4 }
I
\
Figure 9. Circuit for Shifting
to Drive CMOS/HNIL Logic
the Output of the 458/460
PRECISION HIGH CMV ANALOG ISOLATOR
By combining the V/F converter with a floating power supply and optical isolator as shown in Figure 10, accurate low
Ievel measurements in the presence of high common mode
voltages may be achieved. Only the CMV rating of the optical isolator and the breakdown rating of the power supply
limit the CMV rating. Using this approach for isolating transducers, ground loop problems are eliminated. Cost and complexity are minimized since only a single optical isolator is
required to couple the serial pulse outpur from the V/F to
the digital readout.
Figure 10. Optical lsolation Using LED Photo lsolator to
Provide Up to 150OV dc CMV lslation
APPLICATION IN DATA ACQUISITION SYSTEMS
High Noise Immunity Data Transmission, A method of accurately transmitting analog data through high noise environments is illustrated in Figure 11. This approach utilizes the
self clocking output of models 458 and 460 and eliminates
the need for costly additional twisted pair for external synchronization. Model 610 amplifies the low level differential
transducer signal up to the 10V full scale V/F input level.
A differential line driver is used to drive a twisted pair cable,
The differential line driver and receiver offer high noise immunity to common mode noise signals.
!
!
:
" a o o , " o , o " , o u T N T E G R A T E Do v E R ? H o u F s
IOR O.4I67VINTEGRATED FOR 2 DAYS)
Figure 8. Models 458/460 as Long Term lntqrator with
Arbitrary Display Calibration. Frequency Division Ratio can
Otherwise be Chosen to Provide Direct Readout in any
Desired Units.
ANAIOG
METER
0 TO lo&Ht oirrenenrrrr
CMOS/HNIL COMPATIBLEOUTPUT
The circuit shown in Figure 9 may be usedto shift the output
ofthe 458/460from O to +5V to O to +l2Y,ro providea 4V
noiseimmunity for driving high noiseimmunity logic (HNIL)
and CMOSlogic.
Figure 11. Application of Model 458 V/F Converter in a
High Performance,High Noise Rejection Two-Wire Data
TransrnissionSystem
-4-