Contents
Features...........................................................
Applications .....................................................
Block Diagram .................................................
Selection Guide................................................
Pin Assignment ................................................
Absolute Maximum Ratings..............................
Electrical Characteristics ..................................
Measurement Circuits ......................................
Operation .........................................................
Selection of Series Products
and Associated External Components ........
9
1
1
1
2
3
3
4
6
7
Standard Circuits.............................................. 12
Precautions ...................................................... 12
Application Circuits .......................................... 13
Outlines and Dimensions.................................. 15
Marking............................................................ 15
Taping.............................................................. 15
Characteristics of Major Items .......................... 17
Transient Response Characteristics ................. 19
Reference Data................................................ 23
Frequently Asked Questions............................ 26
Rev.6.1
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 16V, it is also suitable when operating via an AC adapter.
n
Features:
n
Applications:
Ÿ
On-board power supplies of battery devices for portable telephones,
Ÿ
Low current consumption:
electronic notebooks, PDAs, and the like.
In operation: 60
mA
max. (A & B Series)
Ÿ
Power supplies for audio equipment, including portable CD players
21
mA
max. (C & D Series)
and headphone stereo equipment.
When powered off: 0.5
mA
max.
Ÿ
Fixed voltage power supply for cameras, video equipment and
Ÿ
Input voltage:
communications equipment.
2.5V to 16V (B & D Series)
Ÿ
Power supplies for microcomputers.
2.5V to 10V (A & C Series)
Ÿ
Conversion from four NiH or NiCd cells or two lithium-ion cells to
Ÿ
Output voltage:
3.3V/3V.
Selectable between 1.5V and 6.0V in steps of 0.1V.
Ÿ
Conversion of AC adapter input to 5V/3V.
Ÿ
Duty ratio:
0% to 100% PWM control (S-8520)
25% to 100% PWM/PFM-switched control (S-8521)
Ÿ
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.)
Ÿ
Oscillation frequency: 180 kHz type. (A & B Series), 60 kHz type. (C & D Series), or 300 kHz type. (version under development).
Ÿ
Soft-start function: 8 msec type. (A & B Series) or 12 msec type (C & D Series).
Ÿ
With power-off function.
Ÿ
With a built-in overload protection circuit. Overload detection time: 4 msec type. (A Series) or 14 msec type. (C Series).
n
Block Diagram:
Tr
VIN
Oscillation
Circuit
L
VOUT
Reference Voltage
Source with Soft Start
EXT
VIN
SD
Cin
PWM or
PWM/PFM-
Switched Control
Circuit
+
-
Cout
ON / OFF
ON / OFF
VSS
Note: The diode inside the IC is a parasitic diode.
Figure 1. Block Diagram
Seiko Instruments Inc.
1
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
n
Selection Guide:
1. Product Name
S - 852 X X XX MC - XXX
-
T2
Rev.6.1
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: Oscillation frequency of 180 kHz, without overload protection circuit.
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
(currently under development).
F: Oscillation frequency of 300 kHz, without overload protection circuit
(currently under development).
Control system
0: PWM control
1: PWM/PFM-switched control
2. Product List (As of Mar. 9, 1998)
A & B Series (Oscillation Frequency of 180 kHz)
Item
Output Voltage (V)
2.5
3.0
3.3
5.0
S-8520AXXMC
Series
S-8520A25MC-AVK-T2
S-8520A30MC-AVP-T2
S-8520A33MC-AVS-T2
S-8520A50MC-AWJ-T2
S-8521AXXMC
Series
S-8521A25MC-AXK-T2
S-8521A30MC-AXP-T2
S-8521A33MC-AXS-T2
S-8521A50MC-AYJ-T2
S-8520BXXMC
Series
S-8520B25MC-ARK-T2
S-8520B30MC-ARP-T2
S-8520B33MC-ARS-T2
S-8520B50MC-ASJ-T2
S-8521BXXMC
Series
S-8521B25MC-ATK-T2
S-8521B30MC-ATP-T2
S-8521B33MC-ATS-T2
S-8521B50MC-AUJ-T2
C & D Series (Oscillation Frequency of 60 kHz)
Item
Output Voltage (V)
2.5
3.0
3.3
5.0
S-8520CXXMC
Series
S-8520C25MC-BRK-T2
S-8520C30MC-BRP-T2
S-8520C33MC-BRS-T2
S-8520C50MC-BSJ-T2
S-8521CXXMC
Series
S-8521C25MC-BTK-T2
S-8521C30MC-BTP-T2
S-8521C33MC-BTS-T2
S-8521C50MC-BUJ-T2
S-8520DXXMC
Series
S-8520D25MC-BVK-T2
S-8520D30MC-BVP-T2
S-8520D33MC-BVS-T2
S-8520D50MC-BWJ-T2
S-8521DXXMC
Series
S-8521D25MC-BXK-T2
S-8521D30MC-BXP-T2
S-8521D33MC-BXS-T2
S-8521D50MC-BYJ-T2
Product samples of the different versions of the series listed above are currently being prepared. Please contact the SII Sales Department
regarding the availability of samples. Also contact SII Sales Department if you desire an output voltage other than those noted above.
2
Seiko Instruments Inc.
Rev.6.1
n
Pin Assignment:
SOT-23-5
Top view
5
4
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Terminal
No.
1
Terminal
Name
Function
Power-off terminal
H: Normal operation (Step-down operation)
deactivated)
ON/OFF
L: Step-down operation stopped (All circuits
2
3
4
5
V
SS
V
OUT
EXT
V
IN
GND terminal
Output voltage monitoring terminal
Connection terminal for external transistor
1
2
3
Figure 2
IC power supply terminal
n
Absolute Maximum Ratings:
Note: Although this IC incorporates an electrostatic protection circuit, the user is urged to avoid subjecting it to an extremely high
static electricity or static voltage in excess of the performance of the said protection circuit.
(Ta = 25
C,
unless otherwise specified)
Item
V
IN
terminal voltage
V
OUT
terminal voltage
ON/OFF terminal voltage
EXT terminal voltage
EXT terminal current
Power dissipation
Operating temperature range
o
Symbol
VIN *1
VOUT
ON/OFF *1
VEXT
IEXT
PD
TOPR
TSTG
Ratings
V
SS
-0.3 to V
SS
+12 or 18
V
SS
-0. 3 to V
IN
+0.3
V
SS
-0.3 to V
SS
+12 or 18
V
SS
-0.3 to V
IN
+0.3
±50
150
-40 to +85
-40 to +125
Unit
V
V
V
V
mA
mW
o
o
Storage temperature range
C
C
*1: VSS+12V for S-8520/21A/C; VSS+18V for S-8520/21B/D
Seiko Instruments Inc.
3
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
n
Electrical Characteristics:
1.
S-8520/21 A & B Series
(Ta = 25
C,
unless otherwise specified)
o
Rev.6.1
Parameter
Output voltage
Input voltage
Current Consumption 1
Current Consumption during
power off
Symbol
VOUT
VIN
Conditions
Min.
VOUT
X 0.976
Typ.
Max.
VOUT
X1.024
10.0
16.0
60
0.5
-
-
-
-
-
-
-
-
-
-
60
60
-
207
216
40
-
0.3
0.1
-0.1
16.0
8.0
-
Units
V
V
Measurement
Circuit
3
2
VOUT
-
-
35
-
-4.5
-7.0
-9.3
-11.3
-13.3
+8.4
+13.2
+17.5
+21.4
+25.1
30
30
±VOUT
x 5E-5
180
180
25
-
-
-
-
8.0
4.0
93
S-8520/21A Series
S-8520/21B Series
2.5
2.5
-
-
ISS1
ISSS
Vout = Output voltage x 1.2
Power-off Pin = 0V
S-8520/21X15
-
24
S-8520/21X25
-
34
S-8520/21X35
-
44
S-8520/21X45
-
54
S-8520/21X55
-
60
S-8520/21X15
-
24
S-8520/21X25
-
34
S-8520/21X35
-
44
S-8520/21X45
-
54
S-8520/21X55
-
60
mA
mA
2
2
-2.3
-3.7
-5.3
-6.7
-8.0
+4.3
+7.0
+9.9
+12.6
+15.0
-
-
-
IEXTH
VEXT = VIN-0.4V
EXT Pin Output Current
mA
-
IEXTL
VEXT = 0.4V
Line Regulation
Load regulation
Output Voltage Temperature
Coefficient
Oscillation Frequency
DVOUT1
Vin = Output voltage x1.2
to
x1.4 *3
DVOUT2
Load current =10uA to IOUT(See below) x1.25
DVOUT
/DTa
fosc
Ta= - 40
C
to 85
C
Measure waveform at
EXT pin
VOUT
³
2.5V
VOUT
£
2.4V
o
o
mV
mV
V/
C
o
3
3
3
153
144
15
1.8
-
-
-
4.0
kHz
3
PWM/PFM-control switch
Duty Ratio
*1
Power-Off Terminal
Input Voltage
Power-Off Terminal
Input Leakage Current
Soft-Start Time
Overload Detection Time *2
Efficiency
PFMDuty Measure waveform at EXT pin under no load.
VSH
VSL
ISH
ISL
TSS
TPRO
EFFI
Duration from the time Vout is reduced to 0V to
the time the EXT terminal obtains Vin.
Evaluate oscillation at EXT pin
Evaluate oscillation stop at EXT pin
%
V
3
2
mA
mA
ms
ms
%
1
1
3
2
3
2.0
-
Conditions:
The recommended components are connected to the IC, unless otherwise indicated. Vin = Vout x 1.2 [V], Iout = 120
[mA] (Vin = 2.5V, if Vout
£
2.0V.)
Peripheral components:
Coil
: Sumida Electric Co.,Ltd. CD54 (47
m
H).
Diode
: Matsushita Electronics Corporation MA720 (Schottky type).
Capacitor
: Matsushita Electronics Corporation TE (16V, 22
m
F tantalum type).
Transistor
: Toshiba 2SA1213Y.
Base resistance (Rb) : 0.68K
W
Base capacitor (Cb)
: 2200 pF (Ceramic type)
The power-off terminal 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: Applicable to the S-8521A Series and S-8521B Series.
*2: Applicable to the S-8520A Series and S-8521A Series.
*3: Vin = 2.5V to 2.94V, if Vout
£
2.0V.
4
Seiko Instruments Inc.
京公网安备 11010802033920号
Copyright © 2005-2026 EEWORLD.com.cn, Inc. All rights reserved
电子工程世界
