EN 59
3139 785 30981
8.
Circuit- and IC description
8.4 IC
Description
8.4.1 Analog
Board
IC7421 - SMPS Control IC
BLOCK
DIAGRAM
d
t
h
SUPP
L
Y
M
ANA
G
E
M
ENT
in
t
e
r
nal
supply
UV
L
O
s
t
a
rt
M
-
level
VCC
1
2
3
G
ND
S
1
CTR
L
FRE
Q
UENCY
CONTRO
L
VO
L
TA
G
E
CONTRO
LL
ED
OSCI
LL
ATOR
L
O
G
IC
L
O
G
IC
OVER-
VO
L
TA
G
E
PROTECTION
OVERPOWER
PROTECTION
sh
ort
winding
s
o
f
t
s
t
a
rt
S2
OVER-
TE
M
PERATURE
PROTECTION
S
Q
R
UV
L
O
Q
M
AXI
M
U
M
ON-TI
M
E
PROTECTION
POWER-ON
RESET
−
1
VA
LL
EY
T
E
A
1507
100 m
V
clamp
DRIVER
START-UP
CURRENT
SOURCE
0.75
V
0.5
V
5
I
sense
6
DRIVER
MG
U2
30
4
DE
M
8
DRAIN
7
H
VS
n.c.
OCP
L
EB
b
lank
I
ss
2
.5
V
b
u
r
s
t
de
t
ec
t
Figure 8-6
PIN DESCRIPTION AND CONFIGURATION
SYMB
O
L P
IN
DESCR
I
P
TION
V
CC
1
supply v
o
l
t
age
G
ND
2
g
ro
und
CTR
L
3
c
o
n
tro
l inpu
t
DE
M
4
inpu
t
f
ro
m auxilia
r
y winding f
or
demagne
t
iza
t
i
o
n
t
iming,
OVP
and
OPP
I
sense
5
p
ro
g
r
amma
b
le cu
rr
en
t
sense inpu
t
DRIVER
6
ga
t
e d
r
ive
r
o
u
t
pu
t
H
VS
7
high v
o
l
t
age safe
t
y space
r
, n
ot
c
o
nnec
t
ed
DRAIN
8
d
r
ain
o
f ex
t
e
r
nal M
OS
swi
t
ch, inpu
t
f
or
s
t
a
rt-
up cu
rr
en
t
and valley sensing
hand
boo
k, halfpage
MG
U2
31
T
E
A
1507
1
2
3
4
VCC
G
ND
CTR
L
DE
M
DRAIN
H
VS
DRIVER
I
sense
8
7
6
5
F
ig.3
P
in c
o
nfigu
r
a
t
i
o
n.