Datasheet

INA139, INA169
5
SBOS181D
www.ti.com
TYPICAL CHARACTERISTICS (Cont.)
At T
A
= +25°C, V+ = 5V, V
IN+
= 12V, and R
L
= 25kΩ, unless otherwise noted.
STEP RESPONSE
20µs/div
1.5V
G = 100
0.5V
1V
G = 100
0V
STEP RESPONSE
10µs/div
1V
G = 50
0V
2V
G = 10
0V
OPERATION
Figure 1 shows the basic circuit diagram for both the INA139
and the INA169. Load current, I
S
, is drawn from the supply,
V
S
, through the shunt resistor, R
S
. The voltage drop in the
shunt resistor, V
S
, is forced across R
G1
by the internal op
amp, causing current to flow into the collector of Q1. The
external resistor, R
L
, converts the output current to a voltage,
V
OUT
, at the OUT pin.
The transfer function for the INA139 is:
I
O
= g
m
(V
IN+
) – (V
IN–
) (1)
where g
m
= 1000µA/V (2)
In the circuit of Figure 1, the input voltage, (V
IN+
) – (V
IN–
), is
equal to I
S
• R
S
and the output voltage, V
OUT
, is equal to
I
O
• R
L
. The transconductance, g
m
, of the INA139 is
1000µA/V. The complete transfer function for the current
measurement amplifier in this application is:
V
OUT
= (I
S
) (R
S
) (1000µA/V) (R
L
) (3)
FIGURE 1. Basic Circuit Connections.
VOLTAGE GAIN EXACT R
L
(Ω) NEAREST 1% R
L
(Ω)
11k 1k
22k 2k
5 5k 4.99k
10 10k 10k
20 20k 20k
50 50k 49k
100 100k 100k
Shunt
R
S
INA139
2
1
OUT
Q1
R
L
I
O
+
V
O
–
Load
R
G1
1kΩ
R
G2
1kΩ
V
IN+
V
IN–
3
4
I
S
V+
5
NOTE: (1) Maximum V
P
and V+ voltage is 60V with the INA169.
V+ power can be
common or
independent of
load supply.
2.7V ≤ (V+) ≤ 40V
(1)
V
P
Load Power Supply
+2.7V to 40V
(1)