OPA569 datasheet(12/28 Pages) TI1

12 / 28 page

OPA569

SBOS264A

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 (RSET, 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, ILIMIT, can be set from 0.2A to 2.2A by

controlling the current through the Current Limit Set pin. The

current limit, ILIMIT, will be 9800 ISET; where ISET 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.

µF

Enable(2)

µF

0.1

µF

Current

Limit Set

µF

12,

14,

17,

0.1

µF

SET (Ω)ILIMIT (A)

23.2k

11.5k

7.68k

5.76k

0.5

1.0

1.5

2.0

SET

(1)

V+

NOTES: (1) R

SET sets the current

limit value from 0.2A to 2.2A.

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.

MONITOR

V–

OPA569

SET

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–

LIMIT = 9800 (1.18V – VADJUST)

SET

14,

17,

14,

17,

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–

LIMIT = 9800 (1.18V/RSET)

the current limit set pin and V–, the negative supply, accord-

ing to the formula:

ILIMIT = 9800 • (1.18V/RSET)

Alternatively, the output current limit can be set by applying

a voltage source in series with a resistance using the equa-

tion:

ILIMIT = 9800 • [(1.18V – VADJUST)/RSET]

The voltage source will be referenced to V–.

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