Voltage Regulators
1
AN8021L, AN8021SB
AC-DC switching power supply control IC
s
Overview
The AN8021L and AN8021SB are ICs which are
suitable for controlling the switching power supply us-
ing primary side control method.
Those are most suited for a switching power supply
of relatively small capacity. Less frequently used func-
tions are removed and only the necessary minimum func-
tions are incorporated, so that they are compact and very
easy to use.
Moreover, the internal settings are incorporated as
much as possible, thus cost down can be realized by de-
creasing the peripheral parts.
s
Features
·
It operates at a control frequency up to 700 kHz, realiz-
ing the output rise time of 35 ns and the output fall time
of 25 ns.
·
Pre-start operating current is as small as 70
µ
A (typical)
so that it is possible to use a miniaturized start resistor.
·
Output block employs totem pole method.
The absolute maximum rating of
±
1.0 A (peak) allows
the direct drive of power MOSFET.
·
Built-in pulse-by-pulse overcurrent protection circuit
·
Built-in protection circuit against malfunction at low
voltage (on/off: 14.2 V/9.2 V)
·
Equipped with timer latch function and overvoltage pro-
tection circuit.
·
Two kinds of packages: 9-pin SIP, 16-pin SOP
s
Applications
·
Various power supply equipment
SIP009-P-0000D
AN8021L
Unit: mm
SSOP016-P-0225B
AN8021SB
Unit: mm
21.7
±0.3
9
8
7
6
5
4
3
2
1
4.3
±0.3
1.0
±0.25
2.7
±0.25
1.4
±0.25
1.35
±0.25
0.4
±0.25
0.5
±0.1
1.2
±0.25
2.54
0.3
+0.1
0.05
0.10
±0.10
1.50
±0.20
0.65
(0.45) 0.80
6.30
±0.30
4.30
±0.30
0.35
±0.10
6.50
±0.30
+0.10
-0.05
0.15
0.50
±0.05
1.00
±0.20
Seating plane
16
9
8
1
Seatng plane
2
AN8021L, AN8021SB
Voltage Regulators
Pin No.
Symbol
Description
1
SS
Soft start pin
2
RT
Resistor connection pin that determines charge and discharge current of triangular wave
3
CT
Triangular wave generating capacitor connection pin
4
CLM(
-
)
Pulse-by-pulse overcurrent protection input pin
5
GND
Grounding pin
6
V
OUT
Power MOSFET direct drive pin
7
V
CC
Power supply voltage pin
8
TIM/OVP
Pin for overvoltage protection and timer latch (joint use)
9
IFB
Current feedback signal input pin from power-supply-output photocoupler
s
Pin Descriptions
·
AN8021L
s
Block Diagram
Note) The number in ( ) shows the pin number for the AN8021SB.
(4)SV
CC
V
REF
Start/Stop
Drive
PWM
Reset
4.1 V
V
CC
(3)PV
CC
7
V
OUT
(2)
6
CLM(
-
)
(15)
4
GND
(1)PGND
5
(16)SGND
TIM/OVP
(5)
8
SS
(11)
1
IFB
(6)
9
OVP
CLM
OSC
OCL
FB
CT
(13)
3
RT
(12)
2
·
AN8021SB
Pin No. Symbol
Description
1
PGND
Grounding pin
2
V
OUT
Power MOSFET direct drive pin
3
PV
CC
Power supply voltage pin
4
SV
CC
Power supply voltage pin
5
TIM/OVP
Pin for overvoltage protection and
timer latch combined use
6
IFB
Power supply output photocoupler
current feedback signal input pin
7
N.C.
N.C.
8
N.C.
N.C.
9
N.C.
N.C.
Pin No. Symbol
Description
10
N.C.
N.C.
11
SS
Soft start pin
12
RT
Charge and discharge current of
triangular wave determining resistance
connection pin
13
CT
Triangular wave generating capacitor
connection pin
14
N.C.
N.C.
15
CLM(
-
)
Pulse-by-pulse overcurrent protection
input pin
16
SGND
Grounding pin
3
Voltage Regulators
AN8021L, AN8021SB
s
Absolute Maximum Ratings
Parameter
Symbol
Rating
Unit
Supply voltage
V
CC
35
V
OVP terminal allowable application voltage
V
OVP
V
CC
V
CLM terminal allowable application voltage
V
CLM
-
0.3 to
+
7.0
V
SS terminal allowable application voltage
V
SS
-
0.3 to
+
7.0
V
Constant output current
I
O
±
150
mA
Peak output current
I
OP
±
1 000
mA
IFB terminal allowable application voltage
I
FB
-
5
mA
Power dissipation
AN8021L
P
D
658
mW
AN8021SB
340
Operating ambient temperature
*
T
opr
-
30 to
+
85
°
C
Storage temperature
*
T
stg
-
55 to
+
150
°
C
s
Recommended Operating Range
Parameter
Symbol
Range
Unit
Timing resistor R
T
R
7
15 to 20
k
Note) *: Expect for the operating ambient temperature and storage temperature, all ratings are for T
a
=
25
°
C.
s
Electrical Characteristics at T
a
=
25
°
C
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Start voltage
V
CC-START
13.0
14.2
15.4
V
Stop voltage
V
CC-STOP
8.5
9.2
9.9
V
Standby bias current
I
CC-STB
V
CC
=
12 V
50
70
105
µ
A
Operating bias current
I
CC-OPR
V
CC
=
34 V
6.4
8.0
9.6
mA
OVP operating bias current 1
I
CC-OVP1
V
CC
=
20 V
2.4
3.0
3.6
mA
OVP operating bias current 2
I
CC-OVP2
V
CC
=
10 V
0.44
0.55
0.66
mA
OVP operating threshold voltage
V
TH-OVP
V
CC
=
18 V
5.4
6.0
6.6
V
OVP release supply voltage
V
CC-OVPC
7.6
8.4
9.2
V
Timer latch charge current
I
CH-TIM
V
CC
=
18 V, R
T
=
19 k
-
20
-
30
-
40
µ
A
Timer latch start feedback current
I
FB-TIM
V
CC
=
18 V
-
0.37
-
0.5
-
0.63
mA
Soft-start charge current
I
CH-SS
V
CC
=
18 V, R
T
=
19 k
-
20
-
30
-
40
µ
A
Overcurrent protection threshold voltage 1
V
TH-CLM1
V
CC
=
18 V
-
180
-
200
-
220
mV
Pre-start low-level output voltage
V
OL-STB
V
CC
=
12 V, I
O
=
10 mA
0.8
1.8
V
Low-level output voltage
V
OL
V
CC
=
18 V, I
O
=
100 mA
1.3
1.8
V
High-level output voltage
V
OH
V
CC
=
18 V, I
O
=
-
100 mA
15.0
16.5
V
Oscillation frequency 1
f
OSC1
V
CC
=
18 V
175
200
225
kHz
Maximum duty 1
Du
max1
V
CC
=
18 V
62
66
70
%
Feedback current at 0% duty
I
FB-Dumin
V
CC
=
18 V
-
1.1
-
1.5
-
1.9
mA
Feedback current at maximum duty
I
FB-Dumax
V
CC
=
18 V
-
0.37
-
0.5
-
0.63
mA
4
AN8021L, AN8021SB
Voltage Regulators
Pin No.
Equivalent circuit
Description
I/O
1
SS:
(11)
Soft start terminal.
When V
CC
is applied, the capacitor connected to
this pin is charged, and the output duty is de-
creased by inputting the capacitor voltage to the
PWM.
2
RT:
(12)
The terminal for connecting a resistor to deter-
mine the charge and discharge current of the
triangular wave.
3
CT:
(13)
The terminal for connecting a capacitor to gen-
erate the triangular wave.
4
CLM(
-
):
I
(15)
The input terminal for pulse-by-pulse
overcurrent protection. It is usually required to
attach an external filter.
5
GND, (PGND), (SGND):
(1)(16)
Grounding terminal.
500
(11)
1
PWM
comp.
500
(12) 2
V
REF
s
Terminal Equivalent Circuits
(13)
V
REF
3
I
O
2I
O
PWM
comp.
Reset
(15)
V
REF
4
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Oscillation frequency 2
f
OSC2
T
a
=
-
30
°
C to
+
85
°
C
160
240
kHz
Overcurrent protection delay time
t
Dry-CLM
V
CC
=
18 V under no load
200
ns
Output voltage rise time
t
r
V
CC
=
18 V under no load
35
ns
Output voltage fall time
t
f
V
CC
=
18 V under no load
25
ns
s
Electrical Characteristics at T
a
=
25
°
C (continued)
·
Design reference data
Note) The characteristics listed below are theoretical values based on the IC design and are not guaranteed.
Note) The number in ( ) shows the pin number for the AN8021SB.
5
Voltage Regulators
AN8021L, AN8021SB
Pin No.
Equivalent circuit
Description
I/O
6
V
OUT
:
O
(2)
The terminal for directly driving a power
MOSFET.
7
V
CC
, (PV
CC
), (SV
CC
):
(3)(4)
Supply voltage terminal.
It monitors the supply voltage and has operat-
ing threshold value for start/stop/OVP reset.
8
TIM/OVP:
I
(5)
The terminal with double functions such as OVP
(overcurrent protection) and timer latch termi-
nal.
[OVP]
When it receives the overvoltage signal of the
power supply output and high is input to the
terminal, internal circuit is turned off. At the
same time, this condition (latch) is hold. To re-
set the OVP latch, it is necessary to reduce V
CC
under the release voltage.
[Timer latch]
The output voltage drop due to the overcurrent
condition of power supply output is detected
through the current level for IFB-input. When
I
IFB
becomes less than current of a certain value,
charge current flows into the capacitor con-
nected to this terminal. When the capacitor is
charged to the threshold voltage of OVP, OVP
starts to operate and the IC stays stop.
9
IFB :
I
(6)
The terminal into which the current feedback
signal is input from the photocoupler of the
power supply output.
s
Terminal Equivalent Circuits (continued)
6 V
500
(5)
Comp.
SV
CC
5
µ
A
8
I/V
conversion
500
(6)
V
REF
9
PWM
comp.
Note) The number in ( ) shows the pin number for the AN8021SB.
(2)
PV
CC
6
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