Philips Semiconductors
Product specification
SMPS control circuit
SG3524
DC ELECTRICAL CHARACTERISTICS
(Continued)
T
A
= 0°C to +70°C, V
IN
= 20V, and f = 20kHz, unless otherwise specified.
SYMBOL
PARAMETER
TEST CONDITIONS
LIMITS
Min
40
V
CE
=40V
I
C
=50mA
V
IN
=20V
R
C
=2kΩ, T
A
=25°C
R
C
=2kΩ, T
A
=25°C
17
0.1
1
18
0.2
0.1
50
2
Typ
Max
UNIT
Output section
(each output)
Collector-emitter voltage (breakdown)
Collector-leakage current
Saturation voltage
Emitter output voltage
t
R
t
F
Rise time
Fall time
(excluding oscillator charging current,
error and current limit dividers, and
with outputs open)
V
µA
V
V
µs
µs
Total standby current
V
IN
=40V
8
10
mA
THEORY OF OPERATION
Voltage Reference
An internal series regulator provides a nominal 5V output which is
used both to generate a reference voltage and is the regulated
source for all the internal timing and controlling circuitry. This
regulator may be bypassed for operation from a fixed 5V supply by
connecting Pins 15 and 16 together to the input voltage. In this
configuration, the maximum input voltage is 6.0V.
This reference regulator may be used as a 5V source for other
circuitry. It will provide up to 50mA of current itself and can easily be
expanded to higher currents with an external PNP as shown in
Figure 3.
Q1
100Ω
+V
IN
15
SG3524
REFERENCE
SECTION
8
16
+
10µF
V
REF
I
L
to 1.0A
DEPENDING
ON CHOICE
FOR Q1
GND
SL00176
Figure 3. Expanded Reference Current Capability
TEST CIRCUIT
I
S
OSC OUT
V
REF
2k
1W
15
3
16
8
6
7
RAMP
V
IN
8–40V
2k
2
N.I.
INPUT
1
INV.
INPUT
9
COMP
SHUT
DOWN
10k
10
4
SG3524
12
13
11
5 14
CURRENT
LIMIT
2k
1W
OUTPUTS
V
IN
0.1
R
T
C
T
10k
2k
1k
SL00177
Figure 4. Test Circuit
1994 Aug 31
3
PHILIPS [ NXP SEMICONDUCTORS ]
