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