Datasheet

OPA569
SBOS264A
12
www.ti.com
APPLICATIONS INFORMATION
BASIC CONFIGURATION
Figure 1 shows the OPA569 connected as a basic non-
inverting amplifier; however, the OPA569 can be used in
virtually any op amp configuration. A current limit setting
resistor (R
SET
, in Figure 1) is essential to the OPA569’s
operation, and cannot be omitted.
Power-supply terminals should be bypassed with low series
impedance capacitors. Using a larger tantalum and smaller
ceramic type in parallel is recommended. Power-supply
wiring should have low series impedance.
POWER SUPPLIES
The OPA569 operates with excellent performance from a
single (+2.7V to +5.5V) supply or from dual supplies. Power
supply voltages do not need to be equal as long as the total
voltage remains below 5.5V. Parameters that vary signifi-
cantly with operating voltage are shown in the typical charac-
teristics section.
ADJUSTABLE CURRENT LIMIT AND CURRENT
LIMIT FLAG PIN
The OPA569 provides over-current protection to the load
through its accurate, user-adjustable current limit (pin 3). The
current limit value, I
LIMIT
, can be set from 0.2A to 2.2A by
controlling the current through the Current Limit Set pin. The
current limit, I
LIMIT
, will be 9800 I
SET
; where I
SET
is the current
through the Current Limit Set pin. Setting the current limit
requires no special power resistors. The output current does
not flow through this pin.
Setting the current limit
As illustrated in Figure 2, the simplest method of setting the
current limit is to connect a resistor or potentiometer between
FIGURE 1. Basic Connections.
FIGURE 2. Setting the Current Limit—Resistor Method.
V
IN
R
1
R
2
47µF
Enable
(2)
47µF
0.1µF
Current
Limit Set
47µF
12,
13
14,
15
19
5
6
8
3
17,
18
0.1µF
R
SET
(Ω)I
LIMIT
(A)
23.2k
11.5k
7.68k
5.76k
0.5
1.0
1.5
2.0
R
SET
(1)
V+
NOTES: (1) R
SET
sets the current
limit value from 0.2A to 2.2A.
R
SET
can be a potentiometer to
easily adjust current limit and
calibrate out errors at the current
limit node. (2) Enable—pull LOW
to disable output.
V
O
I
MONITOR
V–
OPA569
R
SET
V
ADJUST
(1)
(b) Resistor/Voltage Source Method
NOTE: (1) This voltage source must be able to
sink the current from the Current Limit Set pin,
which is I
LIMIT
/9800.
1.18V
V–
I
LIMIT
= 9800 (1.18V – V
ADJUST
)
R
SET
5
6
3
14,
15
17,
18
5
6
3
14,
15
17,
18
R
POT
(a) Resistor or Potentiometer Method
Putting a set resistor in series with the potentiometer
will prevent potential short-circuit on pin.
1.18V
V–
I
LIMIT
= 9800 (1.18V/R
SET
)
the current limit set pin and V–, the negative supply, accord-
ing to the formula:
I
LIMIT
= 9800 • (1.18V/R
SET
)
Alternatively, the output current limit can be set by applying
a voltage source in series with a resistance using the equa-
tion:
I
LIMIT
= 9800 • [(1.18V – V
ADJUST
)/R
SET
]
The voltage source will be referenced to V–.