OPA454 datasheet(21/49 Pages) TI2

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OPA454

-IN

+IN

V-

V+

E/D Com

E/D

OUT

DVDD

(Digital Supply)

5V Logic

V+

(Positive Op Amp Supply)

(Negative Op Amp Supply)

OPA454

www.ti.com

SBOS391B – DECEMBER 2007 – REVISED MARCH 2016

Product Folder Links: OPA454

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9.3.6 ENABLE and E/D Com

If left disconnected, E/D Com is pulled near V– (negative supply) by an internal 10-

μA current source. When left

floating, ENABLE is held approximately 2 V above E/D Com by an internal 1-

μA source. Even though active

operation of the OPA454 results when the ENABLE and E/D Com pins are not connected, a moderately fast,

negative-going signal capacitively coupled to the ENABLE pin can overpower the 1-

μA pullup current and cause

device shutdown. This behavior can appear as an oscillation and is encountered first near extreme cold

temperatures. If the enable function is not used, a conservative approach is to connect ENABLE through a 30-pF

capacitor to a low impedance source. Another alternative is the connection of an external current source from V+

(positive supply) sufficient to hold the enable level above the shutdown threshold. Figure 63 shows a circuit that

connects ENABLE and E/D Com. Choosing RP to be 1 MΩ with a +50-V positive power supply voltage results in

IP = 50 μA.

Figure 63. ENABLE and E/D Com

9.3.7 Current Limit

Figure 23 and Figure 47 to Figure 49 show the current limit behavior of the OPA454. Current limiting is

accomplished by internally limiting the drive to the output transistors. The output can supply the limited current

continuously, unless the die temperature rises to 150°C, which initiates thermal shutdown. With adequate

heatsinking, and use of the lowest possible supply voltage, the OPA454 can remain in current limit continuously

without entering thermal shutdown. Although qualification studies have shown minimal parametric shifts induced

by 1000 hours of thermal shutdown cycling, this mode of operation must be avoided to maximize reliability. It is

always best to provide proper heatsinking (either by a physical plate or by airflow) to remain considerably below

the thermal shutdown threshold. For longest operational life of the device, keep the junction temperature below

125°C.

9.4 Device Functional Modes

A unique mode of the OPA454 is the output disable capability. This function conserves power during idle periods

(quiescent current drops to approximately 150 µA). This disable is accomplished without disturbing the input

signal path, not only saving power but also protecting the load. This feature makes disable useful for

implementing external fault shutdown loops.

OPA454 Datasheet(PDF) 21 Page - Texas Instruments

OPA454 Datasheet(HTML) 21 Page - Texas Instruments

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