CMOS CURRENT MODE
PWM CONTROLLERS
TC18C46
TC28C46
TC38C46
SWITCH
CURRENT
10
3 CURRENT-SENSE
×
AMPLIFIER
"A" = 1
OUTPUT
PWM COMPARATOR
+
4
3
R
+
–
OFF (LOW)
+
–
S
Q
0.65V
RS
–
7
S
PWM LATCH
FROM
UNDERVOLTAGE
LOCKOUT
5.1V
2
V
DD
V
REF
100µA
Q4
ERROR
R1
1
AMPLIFIER
5
6
+
–
+
–
V1
V1
LIMIT
R2
BUFFER
AMPLIFIER
SHUTDOWN
COMPARATOR
Q3
LOCK-UP
AMPLIFIER
16
–
+
+
–
350mV
Q1
L
Q2
6kΩ
POSITIVE
FEEDBACK
TC18C46
TC28C46
TC38C46
350mV
I
3.5kΩ
Figure 1. R1 and R2 Set Maximum Peak Output Current
I
RS
V
OUT
×
3 CURRENT-
SENSE AMPLIFIER
I
× 3 CURRENT-
SENSE
AMPLIFIER
R*
4
3
+
–
4
3
+
RS
C
–
TCx8C46
TCx8C46
*OPTIONAL RC FILTER
(A) Ground Reference
(B) Above-Ground Resistive Sensing
Figure 2. Resistive Sensing
4-106
TELCOM SEMICONDUCTOR, INC.
TELCOM [ TELCOM SEMICONDUCTOR, INC ]
