LM3875T National Semiconductor, LM3875T Datasheet - Page 12

• Manufacturer Part Number: LM3875T
• Description: IC AMP AUDIO PWR 56W AB TO220-11
• Manufacturer: National Semiconductor
• Series: Overture™r
• Type: Class ABr

Specifications of LM3875T

• Output Type: 1-Channel (Mono)
• Max Output Power X Channels @ Load: 56W x 1 @ 8 Ohm
• Voltage - Supply: 20 V ~ 84 V, ±10 V ~ 42 V
• Features: Short-Circuit and Thermal Protection
• Mounting Type: Through Hole
• Package / Case: TO-220-11 (Bent and Staggered Leads)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: *LM3875T; *LM3875T/NOPB; LM3875T/NOPB

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Typical Performance Characteristics
Application Information
GENERAL FEATURES
Under-Voltage Protection: Upon system power-up the
under-voltage Protection Circuitry allows the power supplies
and their corresponding caps to come up close to their full
values before turning on the LM3875 such that no DC output
spikes occur. Upon turn-off, the output of the LM3875 is
brought to ground before the power supplies such that no
transients occur at power-down.
Over-Voltage Protection: The LM3875 contains overvolt-
age protection circuitry that limits the output current to ap-
proximately 4Apeak 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 alternately by sinking large current spikes.
SPiKe Protection: The LM3875 is protected from instanta-
neous peak-temperature stressing by the power transistor
array. The Safe Operating Area graph in the Typical Perfor-
mance Characteristics section shows the area of device
operation where the SPiKe Protection Circuitry is not en-
abled. The waveform to the right of the SOA graph exempli-
fies how the dynamic protection will cause waveform distor-
tion when enabled.
Common-Mode Rejection
Pulse Response
Ratio
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(Continued)
Thermal Protection: The LM3875 has a sophisticated ther-
mal protection scheme to prevent long-term thermal stress
to the device. When the temperature on the die reaches
165˚C, the LM3875 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 device is allowed to heat up to a
relatively high temperature if the fault condition is temporary,
but a sustained fault will cause the device to cycle in a
Schmitt Trigger fashion between the thermal shutdown tem-
perature limits of 165˚C and 155˚C. This greatly reduces the
stress imposed on the IC by thermal cycling, which in turn
improves its reliability under sustained fault conditions.
Since the die temperature is directly dependent upon the
heat sink, the heat sink should be chosen as discussed in
the Thermal Considerations section, such that thermal
shutdown will not be reached during normal operation. Using
the best heat sink possible within the cost and space con-
straints of the system will improve the long-term reliability of
any power semiconductor device.
Large Signal Response
Frequency Response
Open Loop
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