Application Information

MUTE MODE

By placing a logic-high voltage on the mute pin, the signal

going into the amplifiers will be muted. If the mute pin is left

floating or connected to a logic-low level, the amplifier will be

in a non-muted state. Refer to the Typical Performance

Characteristics section for curves concerning Mute Attenu-

ation vs Mute Pin Voltage.

STANDBY MODE

The standby mode of the LM4701 allows the user to drasti-

cally reduce power consumption when the amplifier is idle.

By placing a logic-high voltage on the standby pin, the ampli-

fier will go into Standby Mode. In this mode, the current

drawn from the V

for both amplifiers. The current drawn from the V

typically 2.1 mA. Clearly, there is a significant reduction in

idle power consumption when using the standby mode. Re-

fer to the Typical Performance Characteristics section for

curves showing Supply Current vs Standby Pin Voltage for

both supplies.

UNDER-VOLTAGE PROTECTION

Upon system power-up, the under-voltage protection cir-

cuitry allows the power supplies and their corresponding ca-

pacitors to come up close to their full values before turning

on the LM4701 such that no DC output spikes occur. Upon

turn-off, the output of the LM4701 is brought to ground be-

fore the power supplies such that no transients occur at

power-down.

OVER-VOLTAGE PROTECTION

The LM4701 contains over-voltage protection circuitry that

limits the output current to approximately 3.5 Apk while also

providing voltage clamping, though not through internal

clamping diodes. The clamping effect is quite the same,

however, the output transistors are designed to work alter-

nately by sinking large current spikes.

SPiKe PROTECTION

The

LM4701

is

protected

from

instantaneous

peak-temperature stressing of the power transistor array.

The Safe Operating Area graph in the Typical Performance

Characteristics section shows the area of device operation

where SPiKe Protection Circuitry is not enabled. The wave-

form to the right of the SOA graph exemplifies how the dy-

namic protection will cause waveform distortion when en-

abled.

THERMAL PROTECTION

The LM4701 has a sophisticated thermal protection scheme

to prevent long-term thermal stress of the device. When the

temperature on the die reaches 165˚C, the LM4701 shuts

down. It starts operating again when the die temperature

drops to about 155˚C, but if the temperature again begins to

rise, shutdown will occur again at 165˚C. Therefore, the de-

vice is allowed to heat up to a relatively high temperature if

Pulse Power Limit

DS100835-40

Pulse Power Limit

DS100835-41

Supply Current vs

Case Temperature

DS100835-42

Standby Current (I

Standby Pin Voltage

DS100835-43

Supply Current (I

Standby Pin Voltage

DS100835-44

Input Bias Current vs

Case Temperature

DS100835-45

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