Rev.7.4
_10
PWM Control & PWM/PFM Control
Step-Down Switching Regulator-Controllers
S-8520/8521 Series
The S-8520/8521 Series consists of CMOS step-down switching regulator-
controllers with PWM-control (S-8520) and PWM/PFM-switched control (S-
8521). These devices contain a reference voltage source, oscillation circuit,
error amplifier, and other components.
The S-8520 Series provides low-ripple power, high-efficiency, and excellent
transient characteristics thanks to a PWM control circuit capable of varying
the duty ratio linearly from 0
%
up to 100
%.
The series also contains an
error amplifier circuit as well as a soft-start circuit that prevents overshoot at
startup.
The S-8521 Series works with either PWM control or PFM control, and can
switch from one to the other. It normally operates using PWM control with a
duty ratio of 25
%
to 100
%,
but under a light load, it automatically switches
to PFM control with a duty ratio of 25
%.
This series ensures high efficiency
over a wide range of conditions, from standby mode to operation of
peripheral equipment.
With the addition of an external Pch Power MOS FET or PNP transistor, a coil,
capacitors, and a diode connected externally, these ICs can function as step-down
switching regulators. They serve as ideal power supply units for portable devices
when coupled with the SOT-23-5 minipackage, providing such outstanding features
as low current consumption. Since this series can accommodate an input voltage
of up to 16 V, it is also ideal when operating via an AC adapter.
Features:
Applications:
•
On-board power supplies of battery devices for
•
Low current consumption:
portable telephones, electronic notebooks, PDAs,
In operation: 60
µA
max. (A & B Series)
and the like.
21
µA
max. (C & D Series)
•
Power supplies for audio equipment, including
100
µA
max. (E & F Series)
portable CD players and headphone stereo
When powered off: 0.5
µA
max.
equipment.
•
Input voltage:
•
Fixed voltage power supply for cameras, video
2.5 V to 16 V (B, D, F Series)
equipment and communications equipment.
2.5 V to 10 V (A, C, E Series)
•
Power supplies for microcomputers.
•
Output voltage:
•
Conversion from four NiH or NiCd cells or two
Selectable between 1.5 V and
lithium-ion cells to 3.3 V/3 V.
6.0 V in 0.1 V step
•
Conversion of AC adapter input to 5 V/3 V.
•
Duty ratio:
0
%
to 100
%
PWM control (S-8520)
25
%
to 100
%
PWM/PFM-switched control (S-8521)
•
The only peripheral components that can be used with this IC are a Pch power MOS FET or PNP transistor,
a coil, a diode, and capacitors (If a PNP transistor is used, a base resistance and a capacitor will also be
required).
•
Oscillation frequency: 180 kHz typ. (A & B Series), 60 kHz typ. (C & D Series), or 300 kHz typ. (E, F Series).
•
Soft-start function: 8 ms. typ. (A & B Series) 12 ms. typ.(C & D Series), or 4.5 ms. typ. (E, F Series).
•
With a power-off function.
•
With a built-in overload protection circuit. Overload detection time: 4 ms. typ. (A Series), 14 ms. typ. (C
Series) or 2.6 ms. typ.(E Series).
Seiko Instruments Inc.
1
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.4
_10
Block Diagram:
Tr
VIN
Oscillation
Circuit
L
Reference Voltage
Source with Soft Start
VOUT
EXT
V
IN
C
IN
SD
PWM or
PWM/PFM-
Switched Control
Circuit
+
-
C
OUT
V
ON / OFF
ON / OFF
VSS
Note: The diode inside the IC is a parasitic diode.
Figure 1 Block Diagram
Selection Guide:
1. Product Name
S - 852 X X XX MC - XXX
-
T2
.
Tape specifications
Product name abbreviation.
Package name abbreviation.
Output voltage x 10
Product type:
A: Oscillation frequency of 180 kHz, with overload protection circuit.
B: Oscillati frequency of 180 kHz, without overload protection circuit.
on
C: Oscillation frequency of 60 kHz, with overload protection circuit.
D: Oscillation frequency of 60 kHz, without overload protection circuit.
E: Oscillation frequency of 300 kHz, with overload protection circuit.
F: Oscillation frequency of 300 kHz, without overload protection circuit.
Control system
0: PWM control
1: PWM/PFM-switched control
2
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
Rev.7.4
_10
S-8520/8521 Series
2. Product List (As of September 1, 2000)
A & B Series (Oscillation Frequency of 180 kHz)
Item
Output Voltage
(V)
1.6
1.8
1.9
2.0
2.1
2.5
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.4
3.5
3.6
5.0
S-8520AXXMC
Series
S-8520A21MC-AVG-T2
S-8520A25MC-AVK-T2
S-8520A27MC-AVM-T2
S-8520A28MC-AVN-T2
S-8520A29MC-AVO-T2
S-8520A30MC-AVP-T2
S-8520A31MC-AVQ-T2
S-8520A32MC-AVR-T2
S-8520A33MC-AVS-T2
S-8520A34MC-AVT-T2
S-8520A35MC-AVU-T2
S-8520A36MC-AVV-T2
S-8520A50MC-AWJ-T2
S-8521AXXMC
Series
S-8521A25MC-AXK-T2
S-8521A27MC-AXM-T2
S-8521A28MC-AXN-T2
S-8521A29MC-AXO-T2
S-8521A30MC-AXP-T2
S-8521A31MC-AXQ-T2
S-8521A32MC-AXR-T2
S-8521A33MC-AXS-T2
S-8521A34MC-AXT-T2
S-8521A35MC-AXU-T2
S-8521A36MC-AXV-T2
S-8521A50MC-AYJ-T2
S-8520BXXMC
Series
S-8521BXXMC
Series
S-8520B18MC-ARD-T2 S-8521B18MC-ATD-T2
S-8521B19MC-ATE-T2
S-8521B20MC-ATF-T2
S-8521B21MC-ATG-T2
S-8520B25MC-ARK-T2 S-8521B25MC-ATK-T2
S-8520B27MC-ARM-T2 S-8521B27MC-ATM-T2
S-8520B28MC-ARN-T2 S-8521B28MC-ATN-T2
S-8520B29MC-ARO-T2 S-8521B29MC-ATO-T2
S-8520B30MC-ARP-T2 S-8521B30MC-ATP-T2
S-8520B31MC-ARQ-T2 S-8521B31MC-ATQ-T2
S-8520B32MC-ARR-T2 S-8521B32MC-ATR-T2
S-8520B33MC-ARS-T2 S-8521B33MC-ATS-T2
S-8520B34MC-ART-T2 S-8521B34MC-ATT-T2
S-8520B35MC-ARU-T2 S-8521B35MC-ATU-T2
S-8520B36MC-ARV-T2 S-8521B36MC-ATV-T2
S-8520B50MC-ASJ-T2 S-8521B50MC-AUJ-T2
C & D Series (Oscillation Frequency of 60 kHz)
Item
Output Voltage
(V)
1.6
2.0
2.5
2.7
2.8
2.9
3.0
3.1
3.2
3.3
3.4
3.5
3.6
5.0
S-8520CXXMC
Series
S-8520C25MC-BRK-T2
S-8520C27MC-BRM-T2
S-8520C28MC-BRN-T2
S-8520C29MC-BRO-T2
S-8520C30MC-BRP-T2
S-8520C31MC-BRQ-T2
S-8520C32MC-BRR-T2
S-8520C33MC-BRS-T2
S-8520C34MC-BRT-T2
S-8520C35MC-BRU-T2
S-8520C36MC-BRV-T2
S-8520C50MC-BSJ-T2
S-8521CXXMC
Series
S-8521C16MC-BTB-T2
S-8521C25MC-BTK-T2
S-8521C27MC-BTM-T2
S-8521C28MC-BTN-T2
S-8521C29MC-BTO-T2
S-8521C30MC-BTP-T2
S-8521C31MC-BTQ-T2
S-8521C32MC-BTR-T2
S-8521C33MC-BTS-T2
S-8521C34MC-BTT-T2
S-8521C35MC-BTU-T2
S-8521C36MC-BTV-T2
S-8521C50MC-BUJ-T2
S-8520DXXMC
Series
S-8520D25MC-BVK-T2
S-8520D27MC-BVM-T2
S-8520D28MC-BVN-T2
S-8520D29MC-BVO-T2
S-8520D30MC-BVP-T2
S-8520D31MC-BVQ-T2
S-8520D32MC-BVR-T2
S-8520D33MC-BVS-T2
S-8520D34MC-BVT-T2
S-8520D35MC-BVU-T2
S-8520D36MC-BVV-T2
S-8520D50MC-BWJ-T2
S-8521DXXMC
Series
S-8521D16MC-BXB-T2
S-8521D20MC-BXF-T2
S-8521D25MC-BXK-T2
S-8521D27MC-BXM-T2
S-8521D28MC-BXN-T2
S-8521D29MC-BXO-T2
S-8521D30MC-BXP-T2
S-8521D31MC-BXQ-T2
S-8521D32MC-BXR-T2
S-8521D33MC-BXS-T2
S-8521D34MC-BXT-T2
S-8521D35MC-BXU-T2
S-8521D36MC-BXV-T2
S-8521D50MC-BYJ-T2
E & F Series (Oscillation Frequency of 300 kHz)
Item
Output Voltage
(V)
1.5
1.8
2.0
2.5
2.7
3.0
3.3
3.4
3.5
5.0
S-8520EXXMC
Series
S-8520E18MC-BJD-T2
S-8520E25MC-BJK-T2
S-8520E30MC-BJP-T2
S-8520E33MC-BJS-T2
S-8520E50MC-BKJ-T2
S-8521EXXMC
Series
S-8521E15MC-BLA-T2
S-8521E18MC-BLD-T2
S-8521E20MC-BLF-T2
S-8521E30MC-BLP-T2
S-8521E33MC-BLS-T2
S-8521E35MC-BLU-T2
S-8521E50MC-BMJ-T2
S-8520FXXMC
Series
S-8520F18MC-BND-T2
S-8520F25MC-BNK-T2
S-8520F27MC-BNM-T2
S-8520F30MC-BNP-T2
S-8520F33MC-BNS-T2
S-8520F34MC-BNT-T2
S-8520F50MC-BOJ-T2
S-8521FXXMC
Series
S-8521F18MC-BPD-T2
S-8521F30MC-BPP-T2
S-8521F33MC-BPS-T2
S-8521F50MC-BQJ-T2
For the availability of product samples listed above, contact the SII Sales Department.
Seiko Instruments Inc.
3
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.4
_10
Pin Assignment:
SOT-23-5
Top view
5
4
Pin No.
1
2
3
4
5
Pin Name
Power-off pin
Function
L: Step-down operation stopped (All circuits
deactivated)
ON/OFF
H: Normal operation (Step-down operation)
VSS
VOUT
EXT
VIN
GND pin
Output voltage monitoring pin
Connection pin for external transistor
IC power supply pin
1
2
3
Figure 2
Absolute Maximum Ratings:
(Ta
=
25 C unless otherwise specified)
Item
VIN pin voltage
VOUT pin voltage
ON/OFF pin voltage
EXT pin voltage
EXT pin current
Power dissipation
Operating temperature range
Storage temperature range
Symbol
*1
V
IN
V
OUT
*1
V
ON/OFF
V
EXT
I
EXT
P
D
T
OPR
T
STG
Ratings
V
SS
−0.3
to V
SS
+12
or V
SS
+18
V
SS
−0.3
to V
SS
+12
or V
SS
+18
V
SS
−0.3
to V
SS
+12
or V
SS
+18
V
SS
−0.3
to V
IN
+0.3
±50
250
−40
to
+85
−40
to
+125
Unit
V
V
V
V
mA
mW
ο
C
ο
C
ο
*1.
V
SS
+12
V for S-8520/21A/C/E; V
SS
+18
V for S-8520/21B/D/F
Caution The absolute maximum ratings are rated values exceeding which the product
could suffer physical damage. These values must therefore not be exceeded under
any conditions.
4
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
Rev.7.4
_10
S-8520/8521 Series
Electrical Characteristics:
1. S-8520/21 A & B Series
Parameter
Output voltage
*1
Input voltage
Symbol
V
OUT
(E)
V
IN
Conditions
−
S-8520/21A Series
S-8520/21B Series
Current consumption 1
Current consumption during
power off
I
SS1
I
SSS
V
OUT
=
V
OUT
(S)
×
1.2
V
ON/OFF
=
0 V
S-8520/21X15
−
24
S-8520/21X25
−
34
I
EXTH
V
EXT
=V
IN
−0.4
V
S-8520/21X35
−
44
S-8520/21X45
−
54
EXT pin output current
S-8520/21X55
−
60
S-8520/21X15
−
24
S-8520/21X25
−
34
I
EXTL
V
EXT
=
0.4 V
S-8520/21X35
−
44
S-8520/21X45
−
54
S-8520/21X55
−
60
Line regulation
Load regulation
Output voltage temperature
coefficient
Oscillation frequency
∆V
OUT1
∆V
OUT2
∆V
OUT
/∆Ta
fosc
V
IN
=
V
OUT
(S)
×1.2
to
×1.4
*4
Load current
=10µA
to I
OUT
(See below)
×1.25
Ta=
−
40
°C
to 85
°C
Measure waveform V
OUT
(S)
≥
2.5 V
at EXT pin
V
OUT
(S)
≤
2.4 V
Measure waveform at EXT pin under no
load.
Evaluate oscillation at EXT pin
Evaluate oscillation stop at EXT pin
−
−
−
Duration from the time V
OUT
is reduced
to 0 V to the time the EXT pin obtains
V
IN
.
−
Min.
(Ta
=25 °C,
unless otherwise specified)
Typ.
Max.
Units
V
V
V
OUT
(S)
×1.024
10.0
16.0
60
0.5
−
−
−
−
−
−
−
−
−
−
60
60
−
207
216
40
−
0.3
0.1
0.1
16.0
8.0
−
%
V
µA
µA
ms
ms
%
3
2
1
1
3
2
3
mV
mV
V/°C
kHz
3
3
3
3
mA
−
µA
µA
2
2
V
OUT
(S) V
OUT
(S)
×
0.976
2.5
−
2.5
−
−
−2.3
−3.7
−5.3
−6.7
−8.0
+4.3
+7.0
+9.9
+12.6
+15.0
−
−
−
153
144
15
1.8
−
−0.1
−0.1
4.0
2.0
−
−
35
−
−4.5
−7.0
−9.3
−11.3
−13.3
+8.4
+13.2
+17.5
+21.4
+25.1
30
30
±V
OUT
(S)
×
5E-5
180
180
25
−
−
−
−
8.0
4.0
93
Measurement
Circuit
3
2
PWM/PFM-control switch PFM Duty
*2
duty ratio
Power-Off pin
V
SH
input voltage
V
SL
Power-Off pin
I
SH
input leakage current
I
SL
Soft-Start time
T
SS
T
PRO
Overload detection time
*3
Efficiency
EFFI
Conditions:
The recommended components are connected to the IC, unless otherwise indicated. V
IN
=
V
OUT
(S)
×
1.2 [V],
I
OUT
=
120 [mA] (V
IN
=
2.5 V, if V
OUT
(S)
≤2.0
V.)
Peripheral components:
Coil
: Sumida Electric Co., Ltd. CD54 (47
µH).
Diode
: Matsushita Electronics Corporation MA720 (Schottky type).
Capacitor
: Matsushita Electronics Corporation TE (16 V, 22
µF
tantalum type).
Transistor
: Toshiba Corporation 2SA1213Y.
Base resistance (R
b
)
: 0.68 kΩ
Base capacitor (C
b
)
: 2200 pF (Ceramic type)
The power-off pin is connected to VIN.
Notes:
The output voltage indicated above represents a typical output voltage set up. These specifications apply in
common to both S-8520 and S-8521, unless otherwise noted.
*1.
V
OUT
(S) Specified output voltage value.
V
OUT
(E) Actual output voltage value.
*2.
Applicable to the S-8521A Series and S-8521B Series.
*3.
Applicable to the S-8520A Series and S-8521A Series.
*4.
V
IN
=
2.5 V to 2.94 V, if V
OUT
(S)
≤2.0
V.
Seiko Instruments Inc.
5
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