AD734AN Analog Devices Inc, AD734AN Datasheet - Page 5

• Manufacturer Part Number: AD734AN
• Description: IC MULTIPLIER/DIVIDER 14-DIP
• Manufacturer: Analog Devices Inc

Specifications of AD734AN

• Rohs Status: RoHS non-compliant
• Function: Analog Multiplier
• Number Of Bits/stages: 4-Quadrant
• Package / Case: 14-DIP (0.300", 7.62mm)
• No. Of Pins: 14
• Frequency Max: 10MHz
• No. Of Channels: 6
• Supply Voltage Min: 8V
• Peak Reflow Compatible (260 C): No
• Ic Function: Analog Multiplier IC
• Accuracy: 0.4 %
• Accuracy %: 0.4%
• Output Voltage: 12V
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

REV. C
the AD734 can be operated using the standard (AD534) divider
connections (Figure 8), when the negative feedback path is
established via the Y
(2), we get
In this case, note that the variable X is now the denominator,
and the above restriction (X/U 1.25) on the magnitude of the
X input does not apply. However, X must be positive in order
for the feedback polarity to be correct. Y
summing purposes or connected to the load ground if not
needed. The shorthand form in this case is
In some cases, feedback may be connected to two of the avail-
able inputs. This is true for the square-rooting connections
(Fig-ure 9), where W is connected to both X
X
possibility of again providing a summing input, so setting X
and Y
This is seen more generally to be the geometric-mean function,
since both U and Z can be variable; operation is restricted to
one quadrant. Feedback may also be taken to the U-interface.
Full details of the operation in these modes is provided in the
appropriate section of this data sheet.
Direct Denominator Control
A valuable new feature of the AD734 is the provision to replace
the internal denominator voltage, U, with any value from +10 mV
to +10 V. This can be used (1) to simply alter the multiplier
scaling, thus improve accuracy and achieve reduced noise levels
when operating with small input signals; (2) to implement an
accurate two-quadrant divider, with a 1000:1 gain range and an
asymptotic gain-bandwidth product of 200 MHz; (3) to achieve
certain other special functions, such as AGC or rms.
Figure 2 shows the internal circuitry associated with denomina-
tor control. Note first that the denominator is actually proportional
to a current, Iu, having a nominal value of 356 A for U = 10 V,
whereas the primary reference is a voltage, generated by a buried-
Zener circuit and laser-trimmed to have a very low temperature
coefficient. This voltage is nominally 8 V with a tolerance of
10%.
1
= W and Y
U2
U0
W
U1
1
W
W
= S, we find, in shorthand form
3
4
5
U
Figure 2. Denominator Control Circuitry
28k
Ru
X
Z
2
Qu
1
U
2
= W in Equation (2), and anticipating the
U
X
Iu
Z
2
Qd
1
2
X
Z
input. Substituting W for Y
Z
NOMINALLY
356 A for
U = 10V
Rd
NOM
22.5k
Y
1
.
Y .
S .
NEGATIVE SUPPLY
TC
NOM
8V
AD734
100k
1
Rr
can be used for
Qr
1
and Y
14
13
9
8
2
VP
DD
ER
VN
in Equation
2
LINK TO
DISABLE
. Setting
2
= S
(5)
(6)
(7)
–5–
After temperature-correction (block TC), the reference voltage
is applied to transistor Qd and trimmed resistor Rd, which
generate the required reference current. Transistor Qu and
resistor Ru are not involved in setting up the internal denominator,
and their associated control pins U0, U1 and U2 will normally
be grounded. The reference voltage is also made available, via
the 100 k resistor Rr, at Pin 9 (ER); the purpose of Qr is
explained below.
When the control pin DD (denominator disable) is connected to
VP, the internal source of Iu is shut off, and the collector cur-
rent of Qu must provide the denominator current. The resistor
Ru is laser-trimmed such that the multiplier denominator is
exactly equal to the voltage across it (that is, across pins U1 and
U2). Note that this trimming only sets up the correct internal
ratio; the absolute value of Ru (nominally 28 k ) has a
tolerance of 20%. Also, the alpha of Qu, (typically 0.995)
which might be seen as a source of scaling error, is canceled by
the alpha of other transistors in the complete circuit.
In the simplest scheme (Figure 3), an externally-provided
control voltage, V
resulting voltage across Ru is therefore reduced by one V
example, when V
1.3 V. This error will not be important in some closed-loop
applications, such as automatic gain control (AGC), but clearly
is not acceptable where the denominator value must be well-
defined. When it is required to set up an accurate, fixed value of
U, the on-chip reference may be used. The transistor Qr is
provided to cancel the V
resistor, R2, as shown in Figure 4. R1 is chosen to set the de-
sired value of U and consists of a fixed and adjustable resistor.
Table I shows useful values of the external components for set-
ting up nonstandard denominator values.
R1
V
Figure 4. Connections for a Fixed Denominator
G
Figure 3. Low-Accuracy Denominator Control
NC
NC
4
3
5
4
3
5
U0
U2
U1
U0
U1
U2
G
G
, is applied directly to U0 and U2 and the
= 2 V, the actual value of U will be about
Qu
Qu
Ru
28k
Iu
Iu
Ru
28k
BE
of Qu, and is biased by an external
AD734
AD734
NOM
8V
100k
100k
Rr
Rr
Qr
Qr
DD
VP
ER
VN
VP
DD
ER
VN
14
13
9
8
14
13
AD734
9
8
NC
~
R2
60 A
BE
+V
–V
–V
+V
. For
S
S
S
S