Datasheet

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SBOS057A − OCTOBER 1996 − REVISED FEBRUARY 2007
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10
APPLICATION INFORMATION
OPA237 series op amps are unity-gain stable and suitable
for a wide range of general-purpose applications. Power
supply pins should be bypassed with 10nF ceramic
capacitors.
OPERATING VOLTAGE
OPA237 series op amps operate from single (+2.7V to
+36V) or dual (±1.35V to ±18V) supplies with excellent
performance. Most behavior remains unchanged
throughout the full operating voltage range. Parameters
which vary significantly with operating voltage are shown
in typical performance curves. Specifications are
production tested with +2.7V, +5V, and ±15V supplies.
OUTPUT CURRENT AND STABILITY
OPA237 series op amps can drive large capacitive loads.
However, under certain limited output conditions any op
amp may become unstable. Figure 1 shows the region
where the OPA237 has a potential for instability. These
load conditions are rarely encountered, especially for
single supply applications. For example, take the case
when a +5V supply with a 10kΩ load to V
S
/2 is used.
OPA237 series op amps remain stable with capacitive
loads up to 4,000pF, if sinking current and up to 10,000pF,
if sourcing current. Furthermore, in single-supply
applications where the load is connected to ground, the op
amp is only sourcing current, and as shown Figure 1, can
drive 10,000pF with output currents up to 1.5mA.
20.5 1 1.5
Output Current (mA)
−
2
−
1.5
−
1
−
0.5 0
100k
10k
1k
100
10
Capacitive Load (pF)
V
S
= +2.7V
V
S
=+5V,±15V
OPERATION NOT
RECOMMENDED
Figure 1. Stability-Capacitive Load vs Output
Current
R
L
10
Ω
A1
OPA237
+
R
1
38.3k
Ω
R
3
38.3k
Ω
R
5
383k
Ω
R
6
10k
Ω
R
7
9.09k
Ω
R
4
20k
Ω
R
2
19.1k
Ω
A2
OPA237
R
8
100k
Ω
R
H
10
Ω
I
H
V+
V
−
V+
V
−
2.7V to =
±
15V
V+ for A
1
,A
2
−
In
+In
−
In
+In
V
O
=10
•
I
H
•
R
H
To Load
To Load
V
O
=10
•
I
L
•
R
L
Common−mode range of A2
extends to V
−
for low−side sensing
Optional for I
B
Cancellation
(R
7
=R
6
II R
8
)
R
2
and R
4
divide down the
common−mode input to A1.
Low−Side
Current Sense
High−Side
Current Sense
Out
Out
NOTE: Low and high−side sensing circuits can be used independently.
V
−
for A
1
,A
2
I
L
Figure 2. Low and High-Side Battery Current Sensing