OPA561 datasheet(7/17 Pages) TI1

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OPA561

SBOS206E − DECEMBER 2001 − REVISED FEBRUARY 2007

www.ti.com

APPLICATIONS INFORMATION

Figure 1 shows the OPA561 connected as a basic

noninverting amplifier. However, the OPA561 can be used

in virtually any op amp configuration.

Power-supply terminals should be bypassed with low

series impedance capacitors. The technique of using a

ceramic and tantalum type in parallel is recommended.

Power-supply wiring should have low series impedance.

402k

Ω(3)

µF

0.1

µF

0.1

µF

−

(1)

E/S(2)

MAX = 200µA)

LIM

V+

NOTES: (1) R

CL sets the current limit value

from 0.2A to 1.2A. (2) E/S Pin

Forced

LOW: Output Disable; Indicates LOW:

Thermal Shutdown. (3) 402k

Ωresistor

permanently enables the OPA561.

OPA561

Figure 1. Basic Circuit Connections

POWER SUPPLIES

The OPA561 operates from single (+7V to +15V) or dual

(

±3.5V to ±7.5V) supplies with excellent performance.

Power-supply voltages do not need to be equal. For

example, the positive supply could be set to 10V with the

negative supply at –5V, or vice-versa. Most behaviors

remain unchanged throughout the operating voltage

range. Parameters that vary significantly with operating

voltage are shown in the typical characteristics.

ADJUSTABLE CURRENT LIMIT

The OPA561’s accurate, user-defined, current limit can be

set from 0.2A to 1.2A by controlling the input to the ILIM pin.

Unlike other designs that use a power resistor in series

with the output current path, the OPA561 senses the load

internally. This allows the current limit to be set with

low-power components. In contrast, other designs require

one or two expensive power resistors that can handle the

full output current (1.2A in this case).

Current Limit Accuracy

Separate circuits monitor the positive and negative

currents. Each output is compared to a single internal

reference that is set by the external current limit resistor (or

voltage). The OPA561 employs a patented circuit

technique to achieve an accurate and stable current limit.

The output current limit has an accuracy of up to 5% on the

1A current limit. Due to internal matching limitations, the

positive and negative current limits can be slightly

different. However, the values are typically within 10% of

each other.

Setting the Current Limit

Leaving the ILIM pin open could damage the part.

Connecting ILIM directly to V− programs the maximum

output current limit, typically 1.2A. The simplest method for

adjusting the current limit (ILIM) uses a resistor or

potentiometer connected between the ILIM pin and V−

according to Equation 1:

LIM

1.2V

) 10kW

10, 000

This external resistor determines a small internal current

which sets the desired output current limit. Alternatively,

the output current limit can be set by applying a voltage to

the ILIM pin. Figure 2 shows a simplified schematic of the

OPA561’s current limit.

0.01

µF

(optional, for noisy

environments)

1.2V

10k

Ω

−

LIM =

Max I

O =ILIM

1.2V

CL +10kΩ

() × 10k

Figure 2. Adjustable Current Limit—Resistor

Method

(1)

Not Recommended for New Designs

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