Voltage Regulators
1
AN8038, AN8038S
AC-DC switching power supply control IC
with RCC local resonance circuit for
improved conformance with
energy conservation laws
s
Overview
The AN8038 and AN8038S are self-excited AC-DC
switching power supply control IC that adopt RCC local
resonance control. These ICs are designed to achieve high
efficiency over a wide range of loads (light loads at the
standby mode to heavy loads) for improved conformance
with energy conservation laws, and support input levels
used worldwide. They are particularly appropriate for use
in AV and OA equipments.
s
Features
·
Supports improved conformance with energy conser-
vation laws by providing two operating modes.
With external resistors, it is possible to set the operating
point at which the modes change over according to the
load power, as shown below.
1.Continuous (RCC) mode
High efficiency achieved with local resonance opera-
tion (zero cross detection).
2.Discontinuous mode (standby) mode
Reduced switching loss and standby power due to re-
duced frequency
·
Input voltage correction function. This function corrects
the maximum on-period in a manner inversely propor-
tional to the input voltage.
·
Built-in overvoltage protection function (detects at V
CC
pin)
·
Pulse-by-pulse overcurrent protection function (single detection per one cycle)
·
Packages: 8-pin DIP ··· AN8038
8-pin SOP ··· AN8038S
s
Applications
·
Facsimiles and other OA equipment
·
Printers and other personal computer peripheral equipment
·
AV equipment
DIP008-P-0300B
AN8038
Unit: mm
SOP008-P-0225C
AN8038S
Unit: mm
1
2
3
4
8
7
6
5
9.4±0.3
2.54
6.3±0.3
3.8±0.25
0.15
+0.1
0.05
(3.45)
0.51 min.
1.2±0.25
0.5±0.1
7.62±0.25
3
°
to 15
°
0.50±0.20
0
°
to10
°
0.15±0.10
(1.05)
5.01±0.20
4.30±0.20
6.40±0.20
Seating plane
1.75 max.
1.45±0.10
0.40
+0.10
0.05
0.10
1.27
(0.60)
4
1
5
8
AN8038, AN8038S
Voltage Regulators
2
s
Block Diagram
1
TR
4
IFB
2
5
6
7
CLM
GND
Out
RSTB
OVP
8
V
CC
3
CF
(SD latch)
S
R
Q
(TR latch)
CF
latch
Q
Q
Q
17.5
k
17.5
k
R
Q
INIT
OVP
7 V
7 V
4.2 V
0.25 V
1.0 V
-
0.2 V
I/V
conv.
V
FB
T
ON
T
OFF
High-side
clamp
R Q
S
Low-side
clamp
Current
reviser (IFB)
Current
reviser (ITR)
Start
Stop
Out
drive
V
REF
In
In
Q
S
R
Q
Voltage Regulators
AN8038, AN8038S
3
s
Pin Descriptions
Pin No. Symbol
Description
1
TR
Transformer reset. When a transformer reset is detected, i.e., a low level is input to this pin, the IC
output goes high.
However, the transformer reset signal is ignored during the minimum off-period determined by
the CF pin. The maximum on-period is also corrected according to the current flowing out of this
pin.
2
RSTB
Adjusts the light-load detection level that determines the when the IC switches from RCC to
discontinuous operation. When the voltage (V
FB
) which is I-V conversion of current feedback
signal from IFB pin goes up higher than this pin, minimum off-period current at CF pin decreases,
and operating frequency decreases.
The detection level can be adjusted arbitrarily using an external pull-down resistor.
3
CF
Connection for the capacitor that determines the on and off periods for the IC output (Out).
4
IFB
Input for the current feedback signal from the power supply output photocoupler
5
CLM
Input of the pulse-by-pulse overcurrent protection circuit. Normally, it will be necessary to add
an external filter for this input.
6
GND
Ground
7
V
OUT
Output to drive a power MOSFET directly
8
V
CC
Power supply. This pin watches V
CC
, and has operating threshold voltages for the start, stop,
OVP, and OVP reset levels.
Parameter
Symbol
Range
Unit
Supply voltage
V
CC
From the stop voltage to the OVP operating voltage
V
s
Recommended Operating Range
Note) *1: When mounted on a printed circuit board: 477 mW
*2: When mounted on a printed circuit board: 191 mW
Parameter
Symbol
Rating
Unit
Supply voltage
V
CC
28
V
Peak output current
I
OP
-
1,
+
2
A
Power dissipation
AN8038
P
D
(T
a
=
25
°
C)
500
mW
(Independent IC
P
D
(T
a
=
85
°
C)
260
without a heat sink) AN8038S
P
D
(T
a
=
25
°
C)
306
*1
P
D
(T
a
=
85
°
C)
122
*2
Operating temperature
T
opr
-
30 to
+
85
°
C
Storage temperature
T
stg
-
55 to
+
150
°
C
s
Absolute Maximum Ratings
AN8038, AN8038S
Voltage Regulators
4
s
Electrical Characteristics at V
CC
=
18 V, T
a
=
25
°
C
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Low voltage protection (U.V.L.O.)
Start V
CC
12.9
14.4
15.9
V
initial startup supply voltage.
Low voltage protection (U.V.L.O.)
Stop V
CC
8.0
8.9
9.8
V
operation stop supply voltage
Overvoltage protection (OVP)
OVP V
CC
18.7
20.5
22.3
V
operating supply voltage
Overvoltage protection (OVP)
OVPC V
CC
6.6
7.5
8.4
V
release supply voltage
Overvoltage protection (OVP)
OVP I
CC1
V
CC
=
22 V
10 V
0.4
0.53
0.66
mA
operating time circuit current 1
Overvoltage protection (OVP)
OVP I
CC2
V
CC
=
22 V
18 V
1.3
1.7
2.1
mA
operating time circuit current 2
Transformer reset detection (TR)
TR V
TH
0.15
0.25
0.35
V
threshold voltage
Transformer reset detection (TR)
TR V
CLH
I
TR
=
1 mA
1.2
1.5
1.8
V
upper limit clamp voltage
Transformer reset detection (TR)
TR V
CLL
I
TR
=
-
1 mA
-
0.3
-
0.15
0
V
lower limit clamp voltage
Transformer reset detection (TR)
TR I
TR
V
TR
=
0.5 V
-
5
0
µ
A
pin source current
Overcurrent protection (CLM)
CLM V
TH
-
225
-
205
-
185
mV
threshold voltage
Oscillator (CF) maximum
CF GI
ON
I
FB
=
Open
0.8
1.0
1.2
on-period current gain
Oscillator (CF) maximum
CF I
ON
I
TR
=
0 mA
210
280
350
µ
A
on-period current
Oscillator (CF) minimum
CF I
OFF1
I
IFB
=
-
0.7 mA
-
1 560
-
1 250
-
940
µ
A
off-period current 1
Oscillator (CF) minimum
CF I
OFF2
I
IFB
=
-
1.3 mA
-
70
-
55
-
40
µ
A
off-period current 2
Output oscillator frequency
f
OSC
CF
=
1 000 pF, I
TR
=
-
450
µ
A
105
140
175
kHz
I
IFB
=
-
0.5 mA
Standby pin (RSTB) voltage
V
RSTB
3.2
3.5
3.8
V
Standby operation (RSTB)
RSTB V
TH
0.3
0.5
0.7
V
threshold voltage
Current feedback pin (IFB) voltage
V
IFB
I
IFB
=
-
0.7 mA
5
5.6
6.2
V
Pre-startup low-level output voltage
STB V
OL
V
CC
=
12 V
1.0
1.25
V
Low-level output voltage
V
OL
I
OUT
=
0.2 A
0.9
2.0
V
High-level output voltage
V
OH
I
OUT
=
-
0.1 A
15.5
16.3
V
Circuit current during startup 1
I
START1
120
190
280
µ
A
Circuit current 1
OPR1 I
CC1
V
CC
=
10 V
6.1
8.7
11.3
mA
Circuit current 2
OPR2 I
CC2
V
CC
=
18 V
6.4
9.1
11.8
mA
Voltage Regulators
AN8038, AN8038S
5
Parameter
Symbol
Conditions
Min
Typ
Max
Unit
Low-voltage protection (U.V.L.O.)
V
CC
5.4
V
start/stop supply voltage difference
Transformer reset (TR) detection
TR
V
TH
0.1
V
threshold hysteresis width
Oscillator (CF) upper limit voltage
V
CLH
I
IFB
=
-
0.5 mA, C
F
=
1 000 pF
4.2
V
Oscillator (CF) lower limit voltage 1
V
CFL1
I
IFB
=
-
0.5 mA, C
F
=
1 000 pF
1.0
V
Oscillator (CF) lower limit voltage 2
V
CFL2
I
IFB
=
-
0.2 mA, C
F
=
1 000 pF
0.1
V
Maximum on-period
t
ON(max)
I
IFB
=
-
0.2 mA, C
F
=
1 000 pF
12
µ
s
V
TR
=
0.1 V
Minimum off-period 1
t
OFF(min)1
I
IFB
=
-
0.2 mA, C
F
=
1 000 pF
2.6
µ
s
V
TR
=
0.1 V
Minimum off-period 2
t
OFF(min)2
I
IFB
=
-
1.3 mA, C
F
=
1 000 pF
67
µ
s
I
TR
=
-
450
µ
A
Light-load oscillator frequency
f
OSC2
I
IFB
=
-
1.3 mA, C
F
=
1 000 pF
15
kHz
I
TR
=
-
450
µ
A
Output rise time
t
r
10% to 90%, I
OUT
=
0 mA
40
ns
Output fall time
t
f
10% to 90%, I
OUT
=
0 mA
20
ns
TR output response time
t
TR
400
ns
CLM output response time
t
CLM
100
ns
Circuit current during startup 2
I
START2
T
a
=
-
30
°
C to
+
85
°
C
100
190
300
µ
A
s
Electrical Characteristics at V
CC
=
18 V, 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.
Pin No.
Equivalent Circuit
Description
I/O
1
TR:
I
Transformer reset detection input.
When a transformer reset is detected, i.e., a low
level is input to this pin, the IC output goes high.
However, the transformer reset signal is ignored
if the signal is shorter than the minimum off-
period determined by the C
F
pin. Also note that
the maximum on-period is corrected according
to the source current.
s
Terminal Equivalent Circuits
1
TR
V
REF
7 V
High-side
clamp
Low-side
clamp
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