tp2150b Tripath Technology Inc., tp2150b Datasheet - Page 15

• Manufacturer Part Number: tp2150b
• Description: Dual High Side And Low Side Mosfet Driver
• Manufacturer: Tripath Technology Inc.

T r i p a t h T e c h n o l o g y , I n c . - T e c h n i c a l I n f o r m a t i o n
Output Filter Design
One advantage of Tripath amplifiers over PWM solutions is the ability to use higher-cutoff-
frequency filters. This means load-dependent peaking/droop in the 20kHz audio band potentially
caused by the filter can be made negligible. This is especially important for applications where the
user may select a 6-Ohm or 8-Ohm speaker. Furthermore, speakers are not purely resistive loads
and the impedance they present changes over frequency and from speaker model to speaker
model.
Tripath recommends designing the filter as a 2nd order, 100kHz LC filter. Tripath has obtained
good results with L
= 11uH and C
= 0.15uF for 6: and 8: loads and L
= 18uH and C
= 0.22uF
F
F
F
F
for 4: loads.
The core material of the output filter inductor has an effect on the distortion levels produced by a
TP2150B amplifier. Tripath recommends low-mu type-2 iron powder cores because of their low
loss and high linearity (available from Micrometals, www.micrometals.com).
Tripath also recommends that an RC damper be used after the LC low-pass filter. No-load
operation of a TP2150B amplifier can create significant peaking in the LC filter, which produces
strong resonant currents that can overheat the output MOSFETs and/or other components. The
RC dampens the peaking and prevents problems. Tripath has obtained good results with R
=
Z
20: and C
= 0.15uF for 6: and 8: loads and R
= 15: and C
= 0.22uF for 4: loads.
Z
Z
Z
15
TP2150B - MC/ 1.7/06.04