®
LY8010
2.5 W Mono Filterless Class D Audio power Amplifier (WCSP / DFN)
Rev. 1.6
APPLICATION INFORMATION
Fully Differential Amplifier
The LY8010 is a fully differential amplifier with differential inputs and outputs. The fully differential amplifier
consists of a differential amplifier and a common-mode amplifier. The differential amplifier ensures that the
amplifier outputs a differential voltage on the output that is equal to the differential input times the gain. The
common-mode feedback ensures that the common-mode voltage at the output is biased around VDD/2
regardless of the common-mode voltage at the input. The fully differential LY8010 can still be used with a
single-ended input; however, the LY8010 should be used with differential inputs when in a noisy environment,
like a wireless handset, to ensure maximum noise rejection.
Advantages of Fully Differential Amplifiers
Input-coupling capacitors not required:
The fully differential amplifier allows the inputs to be biased at voltage other than mid-supply. For example,
if a codec has a midsupply lower than the midsupply of the LY8010, the common-mode feedback circuit will
adjust, and the LY8010 outputs will still be biased at midsupply of the LY8010. The inputs of the LY8010 can
be biased from 0.5 V to VDD - 0.8 V. If the inputs are biased outside of that range, input - coupling capacitors
are required.
Midsupply bypass capacitor, C(BYPASS), not required:
The fully differential amplifier does not require a bypass capacitor. This is because any shift in the midsupply
affects both positive and negative channels equally and cancels at the differential output.
Better RF-immunity:
GSM handsets save power by turning on and shutting off the RF transmitter at a rate of 217 Hz. The
transmitted signal is picked-up on input and output traces. The fully differential amplifier cancels the signal
much better than the typical audio amplifier.
Component Selection
Figure 1 shows the LY8010 typical schematic with differential inputs and Figure 2 shows the LY8010
with differential and capacitors inputs , and Figure 3 shows the LY8010 with single-ended inputs.
Differential inputs should be used whenever possible because the single-ended inputs are much more
susceptible to noise.
Table 1. Typical Component Values
Reference
Description
150KΩ
1.0uF
Note
1% tolerance resistors
+22%,-80%
Ri
Cs
Ci
3.3nF
(±10%)
(1) Ci is only needed for single-ended input or if VICM is not between 0.5 V and VDD - 0.8 V. Ci = 3.3 nF
(with Ri = 150KΩ) gives a high-pass corner frequency of 321 Hz.
For example
fc = 1 / ( 2πRiCi )
fc = 1 / ( 2π x 150KΩ x 3.3nF)=321.524 Hz
Lyontek Inc. reserves the rights to change the specifications and products without notice.
5F, No. 2, lndustry E . Rd. IX, Science-Based Industrial Park, Hsinchu 300, Taiwan
TEL: 886-3-6668838
FAX: 886-3-6668836
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