The following specifications apply for V

Ω, LC filter values as shown in Figure 1, unless other-

wise specified. Limits apply for T

Symbol

Parameter

Conditions

LM4681

Units

Typical

Limit

PSRR

Power Supply Rejection Ratio

V

C

input referred

f = 50Hz

f = 60Hz

f = 100Hz

f = 120Hz

f = 1kHz

82

84

92

95

95

dB

Headphone Amplifiers

P

O

Maximum Power Output Per

Channel

THD+N

≤ 1%, R

Ω,

f

94

70

mW

(min)

THD+N

Distortion + Noise

P

Ω,

f

0.02

%

V

NOISE

Output Noise Voltage, RMS

R

Ω,C

BW = 20Hz to 20kHz, R

Ω

A-weighted, Input referred

22

µV

PSRR

Power Supply Rejection Ratio

(Referred to Input)

200mV, 1kHz, V

Ω

77

dB

The following specifications apply for V

Symbol

Parameter

Conditions

LM4681

Units

(Limits )

Typical

(Note 8)

Limit

(Note 7)

C

RANGE

Gain Range

Digital Code = Full Scale, No Load

Power Amplifier

Headphone Amplifier

30

13

29

12

dB (min)

dB (min)

Digital Code = +1LSB, No Load

Power Amplifier

Headphone Amplifier

–48

–65

–46

–63

dB (min)

dB (min)

A

M

Mute Gain

Digital Code = 0, No Load

Power Amplifier

Headphone Amplifier

–76

–74

–74

dB (max)

dB (max)

Note 1: All voltages are measured with respect to the ground pin, unless otherwise specified.

Note 2: “Absolute Maximum Ratings” indicate limits beyond which damage to the device may occur. “Operating Ratings” indicate conditions for which the device

is functional, but do not guarantee specific performance limits. “Electrical Characteristics” state DC and AC electrical specifications under particular test conditions

which guarantee specific performance limits. This assumes that the device is within the Operating Ratings. Specifications are not guaranteed for parameters where

no limit is given, however, the typical value is a good indication of device performance.

Note 3: For operating at case temperatures above 25˚C, the device must be derated based on a 150˚C maximum junction temperature and a thermal resistance

of

Note 4: Human body model, 100pF discharged through a 1.5k

Ω resistor.

Note 5: Machine Model 220pF − 240pF discharged through all pins.

Note 6: The operating junction temperature maximum is 150˚C.

Note 7: Limits are guaranteed to National’s AOQL (Average Outgoing Quality Level).

Note 8: Typicals are measured at 25˚C and represent the parametric norm.

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