Tripath Technology, Inc. - Technical Information
1/2 TA2022
V5
RFBA
RFBA
RFBC
RFBC
Processing
&
FBKOUT1
FBKGND1
OUT1
OUT 1 GROUND
Modulation
RFBB
AGND
RFBB
Figure 2: Modulator Feedback
The modulator feedback resistors are:
R
R
FBA = User specified, typically 1KΩ
R
FBA * VPP
FBB
=
(VPP - 4)
R
FBA * VPP
R
A
FBC
=
4
R
FBC * (RFBA + RFBB )
V - MODULATOR
≈
+ 1
R
FBA * RFBB
The above equations assume that VPP=|VNN|.
For example, in a system with VPPMAX=36V and VNNMAX=-36V,
R
FBA = 1kΩ, 1%
RFBB = 1.125kΩ, use 1.13kΩ, 1%
RFBC = 9.0kΩ, use 9.09kΩ, 1%
The resultant modulator gain is:
9.09k Ω * (1.0k Ω + 1.13k Ω)
A
V - MODULATOR
≈
+ 1 = 18.13V/V
1.0k Ω * 1.13k Ω
17
TA2022 – KLI/1.2/07-04