OPA452, 453

9

SBOS127C

www.ti.com

APPLICATIONS INFORMATION

Figure 1 shows the OPA452 connected as a basic noninverting

amplifier. The OPA452 can be used in virtually any op amp

configuration. The OPA453 is designed for use in configura-

tions with gains of 5 or greater. Power-supply terminals

should be bypassed with 0.1

µF capacitors, or greater, near

the power-supply pins. Be sure that the capacitors are

appropriately rated for the power-supply voltage used. The

OPA452 and OPA453 can supply output currents up to

50mA with excellent performance.

FIGURE 1. Basic Circuit Connections.

CURRENT LIMIT

The OPA452 and OPA453 are designed with internal cur-

rent-limiting circuitry that limits the output current to approxi-

mately 125mA. The current limit varies slightly with increas-

ing junction temperature and supply voltage, as shown in the

Typical Characteristics. Current limit, in combination with the

thermal protection circuitry, provides protection from most

types of overload conditions including short-circuit to ground.

THERMAL PROTECTION

The OPA452 and OPA453 have thermal shutdown circuitry

that protects the amplifier from damage caused by overload

conditions. The thermal protection circuitry disables the out-

put when the junction temperature reaches approximately

160

°C, allowing the device to cool. When the junction tem-

perature cools to approximately 140

°C, the output circuitry is

automatically re-enabled.

The thermal shutdown function is not intended to replace

proper heat sinking. Activation of the thermal shutdown

circuitry is an indication of excessive power dissipation or an

inadequate heat sink. Continuously running the amplifier into

thermal shutdown can degrade reliability.

The Thermal Shutdown Indicator (Flag) pin can be monitored

to determine if shutdown is occurring. During normal opera-

tion, the current output from the flag pin is typically 50nA.

During shutdown, the current output from the flag pin in-

creases to 140

µA (typical). This current output allows for

easy interfacing to external logic. Figure 2 shows two ex-

amples implementing this function.

FIGURE 2. Thermal Shutdown Indicator.

G = 1+

R

2

R

1

Z

L

R

2

R

1

0.1

µF

10

µF

OPA452

V–

V+

+

+

V

IN

10

µF

0.1

µF

V

O

Flag

(optional)

Flag

100

µA to

165

µA

HCT

OPA452

Logic

Ground

V

OUT

+5V

19.1k

Ω

+5V

V

OUT

CMOS

OPA452

Logic

Ground

Interfacing with CMOS Logic

Interfacing with HCT Logic

39k

Ω

Interface to virtually any CMOS

logic gate by choosing a resistor

value that provides an assured

logic high voltage with the

minimum (100

µA) flag current.

HCT logic has relatively well-

controlled logic level. A properly

chosen resistor value can

assure proper logic high level

throughout the full range of flag

output current.