LM4665LD National Semiconductor, LM4665LD Datasheet - Page 10

• Manufacturer Part Number: LM4665LD
• Manufacturer: National Semiconductor

Specifications of LM4665LD

• Operational Class: Class-AB
• Audio Amplifier Output Configuration: 1-Channel Mono
• Output Power (typ): 1.4x1@8OhmW
• Audio Amplifier Function: Speaker
• Total Harmonic Distortion: 0.8@8Ohm@400mW%
• Single Supply Voltage (typ): 3/5V
• Dual Supply Voltage (typ): Not RequiredV
• Power Supply Requirement: Single
• Rail/rail I/o Type: No
• Power Supply Rejection Ratio: 52dB
• Single Supply Voltage (min): 2.7V
• Single Supply Voltage (max): 5.5V
• Dual Supply Voltage (min): Not RequiredV
• Dual Supply Voltage (max): Not RequiredV
• Operating Temp Range: -40C to 85C
• Operating Temperature Classification: Industrial
• Mounting: Surface Mount
• Pin Count: 10
• Package Type: LLP EP
• Lead Free Status / Rohs Status: Not Compliant

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Application Information
the output pins to the load and the supply pins to the power
supply should be as wide as possible to minimize trace
resistance.
The rising and falling edges are necessarily short in relation
to the minimum pulse width (160ns), having approximately
2ns rise and fall times, typical, depending on parasitic output
capacitance. The inductive nature of the transducer load can
also result in overshoot on one or both edges, clamped by
the parasitic diodes to GND and V
EMI standpoint, this is an aggressive waveform that can
radiate or conduct to other components in the system and
cause interference. It is essential to keep the power and
output traces short and well shielded if possible. Use of
ground planes, beads, and micro-strip layout techniques are
all useful in preventing unwanted interference.
POWER SUPPLY BYPASSING
As with any power amplifier, proper supply bypassing is
critical for low noise performance and high power supply
rejection ratio (PSRR). The capacitor (C
as close as possible to the LM4665. Typical applications
employ a voltage regulator with a 10µF and a 0.1µF bypass
capacitors that increase supply stability. These capacitors do
not eliminate the need for bypassing on the supply pin of the
LM4665. A 1µF tantalum capacitor is recommended.
SHUTDOWN FUNCTION
In order to reduce power consumption while not in use, the
LM4665 contains shutdown circuitry that reduces current
draw to less than 0.01µA. In addition, the LM4665 contains a
Shutdown Mode pin allowing the designer to designate
whether the shutdown circuitry is activated by either a High
level logic signal or a Low level logic signal. The Shutdown
Mode pin should be permanently connected to either GND
(Low) or V
shutdown by toggling the Shutdown pin to the same state as
the Shutdown Mode pin. For simplicity’s sake, this is called
"Shutdown same", as the LM4665 enters into a shutdown
state whenever the two pins are in the same logic state. The
trigger point for either shutdown high or shutdown low is
shown as a typical value in the Electrical Characteristics
Tables and in the Shutdown Hysteresis Voltage graphs
found in the Typical Performance Characteristics section.
It is best to switch between ground and supply for minimum
current usage while in the shutdown state. While the
LM4665 may be disabled with shutdown voltages in between
ground and supply, the idle current will be greater than the
typical 0.01µA value. Increased THD may also be observed
with voltages greater than GND and less than V
Shutdown pin when in PLAY mode.
DD
(High). The LM4665 may then be placed into
DD
in each case. From an
S
) location should be
(Continued)
DD
on the
10
The LM4665 has an internal resistor connected between the
Shutdown Mode and Shutdown pins. The purpose of this
resistor is to eliminate any unwanted state changes when
the Shutdown pin is floating, as long as the Shutdown Mode
pin is connected to GND or V
pin is properly connected, the LM4665 will enter the shut-
down state when the Shutdown pin is left floating or if not
floating, when the shutdown voltage has crossed the corre-
sponding threshold for the logic level assigned by the Shut-
down Mode pin voltage. To minimize the supply current while
in the shutdown state, the Shutdown pin should be driven to
the same potential as the Shutdown Mode pin or left floating.
The amount of additional current due to the internal shut-
down resistor can be found by Equation (1) below.
With only a 0.5V difference between the Shutdown Mode
voltage and the Shutdown voltage an additional 8.3µA of
current will be drawn while in the shutdown state.
GAIN SELECTION FUNCTION
The LM4665 has fixed selectable gain to minimize external
components, increase flexibility and simplify design. For a
differential gain of 6dB (2V/V), the Gain Select pin should be
permanently connected to V
For a differential gain of 12dB (4V/V), the Gain Select pin
should be permanently connected to GND or driven to a
logic low level. The gain of the LM4665 can be switched
while the amplifier is in PLAY mode driving a load with a
signal without damage to the IC. The voltage on the Gain
Select pin should be switched quickly between GND (logic
low) and V
artifacts from appearing at the output. For typical threshold
voltages for the Gain Select function, refer to the Gain
Threshold Voltages graph in the Typical Performance
Characteristics section.
INCREASING SUPPLY VOLTAGE RANGE
When using the micro SMD package (ITL), the operating
supply voltage range is 2.7V - 3.8V with an 8Ω speaker load.
To increase the operating supply voltage range, four Schot-
tky diodes (D
undershoot of the output pulse waveform (See Figure 2
below). To reduce THD+N, small value capacitors in the
range of 10pF - 33pF (C
needed. The diodes should be placed as close to the micro
SMD package as possible.
DD
1
(logic high) to eliminate any possible audible
- D
(V
4
SD MODE
) can be used to control the over and
N1
DD
- V
& C
DD
or driven to a logic high level.
SD
. When the Shutdown Mode
N2
) / 60kΩ
) can also be added as
(1)