Datasheet

G
DA
VCC
R
TA
R
SA
R
OA
CSA
VCC
R
TB
R
SB
R
OB
G
DB
C
TA
C
TB
D
PA1
D
PA2
D
PB1
D
PB2
UCC28070
SLUS794E – NOVEMBER 2007–REVISED APRIL 2011 www.ti.com
Current Sense Offset and PWM Ramp for Improved Noise Immunity
To improve noise immunity at extremely light loads, a PWM ramp with a dc offset is recommended to be added
to the current sense signals. Electrical components R
TA
, R
TB
, R
OA
, R
OB
, C
TA
, C
TB
, D
PA1
, D
PA2
, D
PB1
, D
PB1
C
TA
,
C
TB
form a PWM ramp that is activated and deactivated by the gate drive outputs of the UCC28070. Resistor
R
OA
and R
OB
add a dc offset to the CS resistors (R
SA
and R
SB
).
Figure 26. PWM Ramp and Offset Circuit
36 Copyright © 2007–2011, Texas Instruments Incorporated