INA170EA250 Burr-Brown Corporation, INA170EA250 Datasheet - Page 6

• Manufacturer Part Number: INA170EA250
• Description: High-Side/ Bidirectional CURRENT SHUNT MONITOR
• Manufacturer: Burr-Brown Corporation

FIGURE 1. Basic Circuit Connections.
6
OPERATION
Figure 1 shows the basic circuit diagram for the INA170.
Load current I
resistor R
across R
into the collector of Q1. External resistor R
output current to a voltage, V
Without offset, the transfer function for the INA170 is:
In the circuit of Figure 1, the input voltage, (V
equal to I
I
1000 A/V. The complete transfer function for the current
measurement amplifier in this application is:
Applying a positive reference voltage to pin 3 causes a
current to flow through R
offset from zero. The transfer function then becomes:
The maximum differential input voltage for accurate mea-
surements is 0.5V, which produces a 500 A output current.
A differential input voltage of up to 2V will not cause
damage. Differential measurements (pins 1 and 2) can be
O
• R
VOLTAGE GAIN
L
. The transconductance, g
G1
100
S
10
20
50
S
1
2
5
. The voltage drop in shunt resistor V
V
by the internal op-amp, causing current to flow
• R
V
OUT
OUT
S
S
and the output voltage, V
is drawn from supply V
where g
= (I
I
O
V
S
REF
= g
) (R
R
EXACT R
OS
OS
m
•
m
S
R
100k
, forcing output current I
10k
20k
50k
(V
) (1000 A/V) (R
1k
2k
5k
= 1000 A/V
L
OUT
IN
L
+
( )
– V
, at the OUT pin.
I
m
S
IN
–
, of the INA170 is
•
)
1
R
NEAREST 1% R
k
S
•
S
OUT
R
through shunt
L
L
L
4.99k
)
100k
converts the
, is equal to
IN
10k
20k
49k
+
1k
2k
S
– V
is forced
O
V+ power can be
common or
independent of
load supply.
IN
L
2.7
–
to be
( )
Load Power Supply
), is
(1)
(2)
(3)
(4)
www.ti.com
+2.7 to 60V
(V+)
V
P
40V
V
bipolar with a more-positive voltage applied to pin 2. If a
more-negative voltage is applied to pin 1, output current I
will decrease towards zero.
BASIC CONNECTION
Figure 1 shows the basic connection of the INA170. The
input pins, V
possible to the shunt resistor to minimize any resistance in
series with the shunt resistance. The output resistor, R
shown connected between pin 6 and ground. Best accuracy
is achieved with the output voltage measured directly across
R
where load current could flow in the ground connections,
affecting the measurement accuracy.
No power-supply bypass capacitors are required for stability
of the INA170. However, applications with noisy or high
impedance power supplies may require de-coupling capaci-
tors to reject power-supply noise. Connect bypass capacitors
close to the device pins.
POWER SUPPLIES
The input circuitry of the INA170 can accurately measure
beyond its power-supply voltage, V+. For example, the V+
power supply can be 5V, while the load power-supply
voltage (INA170 input voltage) is up to +60V. However, the
output-voltage range of the OUT terminal (pin 6) is limited
by the supply.
SELECTING R
The value chosen for the shunt resistor, R
application and is a compromise between small-signal accu-
racy and maximum permissible voltage loss in the measure-
ment line. High values of R
REF
L
. This is especially important in high-current systems
V+
8
3
INA170
IN
+
5
and V
S
R
OS
AND R
1k
R
G1
V
IN
IN
Q2
+
–
2
, should be connected as closely as
Shunt
R
S
L
S
4
provide better accuracy at lower
1
V
1k
IN
R
–
G2
I
S
Q1
OUT
6
S
, depends on the
I
0
Load
INA170
R
SBOS193B
L
V
+
–
O
L
, is
O