Rev.7.5_00
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE
SWITCHING REGULATOR CONTROLLER
S-8520 / 8521 Series
Seiko Instruments Inc. 1
The S-8520 / 8521 Series consists of CMOS step-down
switching regulator-controllers with PWM control (S-8520
Series) and PWM / PFM switching control (S-8521
Series). 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 small
package, 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
• Low current consumption During operation: 60 µA max. (A, B types)
21 µA max. (C, D types)
100 µA max. (E, F types)
During shutdown: 0.5 µA max.
• Input voltage: 2.5 to 16 V (B, D, F types)
2.5 to 10 V (A, C, E types)
• Output voltage: Selectable between 1.5 V and 6.0 V in 0.1 V step
• Duty ratio: 0 to 100% PWM control (S-8520 Series)
25 to100% PWM / PFM switching control (S-8521 Series)
• 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 types)
60 kHz typ. (C, D types)
300 kHz typ. (E, F types)
• Soft-start function: 8 ms. typ. (A, B types)
12 ms. typ. (C, D types)
4.5 ms. typ. (E, F types)
• With a shutdown function
• With a built-in overload protection circuit Overload detection time: 4 ms. typ. (A type)
14 ms. typ. (C type)
2.6 ms. typ. (E type)
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
2 Seiko Instruments Inc.
Applications
• On-board power supplies of battery devices for portable telephones, electronic notebooks, PDAs.
• Power supplies for audio equipment, including portable CD players and headphone stereo equipment.
• Fixed voltage power supply for cameras, video equipment and communications equipment.
• Power supplies for microcomputers.
• Conversion from four NiH or NiCd cells or two lithium-ion cells to 3.3 V / 3 V.
• Conversion of AC adapter input to 5 V / 3 V.
Package
Drawing code
Package Name Package Tape Reel
SOT-23-5 MP005-A MP005-A MP005-A
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 3
Block Diagrams
1. S-8520 Series
VOUT
VSS
L
SD COUT
−
+
VIN
T
r
EXT
VIN
CIN
+
PWM control
circuit
+
Reference voltage source
with soft-start
Oscillation
circuit
OFF/ON
OFF/ONV
Remark All the diodes in the figure are parasitic diodes.
Figure 1
2. S-8521 Series
VOUT
VSS
L
SD COUT
−
+
VIN
T
r
EXT
VIN
CIN
+
PWM/PFM
switching control
circuit
+
Reference voltage source
with soft-start
Oscillation
circuit
OFF/ON
OFF/ONV
Remark All the diodes in the figure are parasitic diodes.
Figure 2
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
4 Seiko Instruments Inc.
Product Name Structure
• The control types, product types, and output voltage for the S-8540 / 8541 series can be selected at the
user’s request. Please refer to the “1. Product name” for the definition of the product name and “2.
Product Name List” for the full product names.
1. Product name
S-852 x x xx MC - xxx - T2
IC direction in tape specifications*1
Product code*2
Package code
MC: SOT-23-5
Output voltage
15 to 60
(Ex. When the output voltage is 1.5 V, it is expressed as 15.)
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.
F: Oscillation frequency of 300 kHz,
Without overload protection circuit.
Control system
0: PWM control
1: PWM/PFM switching control
*1. Refer to the taping specifications at the end of this book.
*2. Refer to “2. Product name list”.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 5
2. Product name list
2. 1 S-8520 Series
Table 1 (1 / 2)
Series
Output voltage [V] S-8520AxxMC Series S-8520BxxMC Series S-8520CxxMC Series
1.8
S-8520B18MC-ARD-T2
2.1 S-8520A21MC-AVG-T2
2.4
S-8520B24MC-ARJ-T2
2.5 S-8520A25MC-AVK-T2 S-8520B25MC-ARK-T2 S-8520C25MC-BRK-T2
2.6 S-8520A26MC-AVL-T2
2.7 S-8520A27MC-AVM-T2 S-8520B27MC-ARM-T2 S-8520C27MC-BRM-T2
2.8 S-8520A28MC-AVN-T2 S-8520B28MC-ARN-T2 S-8520C28MC-BRN-T2
2.9 S-8520A29MC-AVO-T2 S-8520B29MC-ARO-T2 S-8520C29MC-BRO-T2
3.0 S-8520A30MC-AVP-T2 S-8520B30MC-ARP-T2 S-8520C30MC-BRP-T2
3.1 S-8520A31MC-AVQ-T2 S-8520B31MC-ARQ-T2 S-8520C31MC-BRQ-T2
3.2 S-8520A32MC-AVR-T2 S-8520B32MC-ARR-T2 S-8520C32MC-BRR-T2
3.3 S-8520A33MC-AVS-T2 S-8520B33MC-ARS-T2 S-8520C33MC-BRS-T2
3.4 S-8520A34MC-AVT-T2 S-8520B34MC-ART-T2 S-8520C34MC-BRT-T2
3.5 S-8520A35MC-AVU-T2 S-8520B35MC-ARU-T2 S-8520C35MC-BRU-T2
3.6 S-8520A36MC-AVV-T2 S-8520B36MC-ARV-T2 S-8520C36MC-BRV-T2
4.3
S-8520B43MC-ASC-T2
5.0 S-8520A50MC-AWJ-T2 S-8520B50MC-ASJ-T2 S-8520C50MC-BSJ-T2
5.3
S-8520B53MC-ASM-T2
Table 1 (2 / 2)
Series
Output voltage [V] S-8520DxxMC Series S-8520ExxMC Series S-8520FxxMC Series
1.5
S-8520F15MC-BNA-T2
1.6
S-8520E16MC-BJB-T2
1.8
S-8520E18MC-BJD-T2 S-8520F18MC-BND-T2
2.0
S-8520F20MC-BNF-T2
2.5 S-8520D25MC-BVK-T2 S-8520E25MC-BJK-T2 S-8520F25MC-BNK-T2
2.6
S-8520F26MC-BNL-T2
2.7 S-8520D27MC-BVM-T2
S-8520F27MC-BNM-T2
2.8 S-8520D28MC-BVN-T2
2.9 S-8520D29MC-BVO-T2
3.0 S-8520D30MC-BVP-T2 S-8520E30MC-BJP-T2 S-8520F30MC-BNP-T2
3.1 S-8520D31MC-BVQ-T2
S-8520F31MC-BNQ-T2
3.2 S-8520D32MC-BVR-T2
3.3 S-8520D33MC-BVS-T2 S-8520E33MC-BJS-T2 S-8520F33MC-BNS-T2
3.4 S-8520D34MC-BVT-T2
S-8520F34MC-BNT-T2
3.5 S-8520D35MC-BVU-T2
3.6 S-8520D36MC-BVV-T2
5.0 S-8520D50MC-BWJ-T2 S-8520E50MC-BKJ-T2 S-8520F50MC-BOJ-T2
5.2
S-8520E52MC-BKL-T2
5.5
S-8520F55MC-BOO-T2
Remark Please contact the SII marketing department for the availability of product samples other than
those specified above.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
6 Seiko Instruments Inc.
2-2. S-8521 Series
Table 2 (1 / 2)
Series
Output voltage [V] S-8521AxxMC Series S-8521BxxMC Series S-8521CxxMC Series
1.5
S-8521B15MC-ATA-T2
1.6
S-8521C16MC-BTB-T2
1.8
S-8521B18MC-ATD-T2
1.9
S-8521B19MC-ATE-T2
2.0
S-8521B20MC-ATF-T2
2.1
S-8521B21MC-ATG-T2
2.3
S-8521B23MC-ATI-T2
2.5 S-8521A25MC-AXK-T2 S-8521B25MC-ATK-T2 S-8521C25MC-BTK-T2
2.6
S-8521B26MC-ATL-T2
2.7 S-8521A27MC-AXM-T2 S-8521B27MC-ATM-T2 S-8521C27MC-BTM-T2
2.8 S-8521A28MC-AXN-T2 S-8521B28MC-ATN-T2 S-8521C28MC-BTN-T2
2.9 S-8521A29MC-AXO-T2 S-8521B29MC-ATO-T2 S-8521C29MC-BTO-T2
3.0 S-8521A30MC-AXP-T2 S-8521B30MC-ATP-T2 S-8521C30MC-BTP-T2
3.1 S-8521A31MC-AXQ-T2 S-8521B31MC-ATQ-T2 S-8521C31MC-BTQ-T2
3.2 S-8521A32MC-AXR-T2 S-8521B32MC-ATR-T2 S-8521C32MC-BTR-T2
3.3 S-8521A33MC-AXS-T2 S-8521B33MC-ATS-T2 S-8521C33MC-BTS-T2
3.4 S-8521A34MC-AXT-T2 S-8521B34MC-ATT-T2 S-8521C34MC-BTT-T2
3.5 S-8521A35MC-AXU-T2 S-8521B35MC-ATU-T2 S-8521C35MC-BTU-T2
3.6 S-8521A36MC-AXV-T2 S-8521B36MC-ATV-T2 S-8521C36MC-BTV-T2
4.0
S-8521B40MC-ATZ-T2
4.4
S-8521B44MC-AUD-T2
5.0 S-8521A50MC-AYJ-T2 S-8521B50MC-AUJ-T2 S-8521C50MC-BUJ-T2
Table 2 (2 / 2)
Series
Output voltage [V] S-8521DxxMC Series S-8521ExxMC Series S-8521FxxMC Series
1.5
S-8521E15MC-BLA-T2 S-8521F15MC-BPA-T2
1.6 S-8521D16MC-BXB-T2 S-8521E16MC-BLB-T2
1.7
S-8521E17MC-BLC-T2
1.8
S-8521E18MC-BLD-T2 S-8521F18MC-BPD-T2
1.9
S-8521E19MC-BLE-T2 S-8521F19MC-BPE-T2
2.0 S-8521D20MC-BXF-T2 S-8521E20MC-BLF-T2
2.5 S-8521D25MC-BXK-T2 S-8521E25MC-BLK-T2 S-8521F25MC-BPK-T2
2.7 S-8521D27MC-BXM-T2
2.8 S-8521D28MC-BXN-T2
2.9 S-8521D29MC-BXO-T2
3.0 S-8521D30MC-BXP-T2 S-8521E30MC-BLP-T2 S-8521F30MC-BPP-T2
3.1 S-8521D31MC-BXQ-T2
3.2 S-8521D32MC-BXR-T2
3.3 S-8521D33MC-BXS-T2 S-8521E33MC-BLS-T2 S-8521F33MC-BPS-T2
3.4 S-8521D34MC-BXT-T2
S-8521F34MC-BPT-T2
3.5 S-8521D35MC-BXU-T2 S-8521E35MC-BLU-T2
3.6 S-8521D36MC-BXV-T2
4.0 S-8521D40MC-BXZ-T2
5.0 S-8521D50MC-BYJ-T2 S-8521E50MC-BMJ-T2 S-8521F50MC-BQJ-T2
Remark Please contact the SII marketing department for the availability of product samples other than
those specified above.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 7
Pin Configuration
Table 3
Pin No. Pin name Pin description
1
OFF/ON Shutdown pin
“H”:
Normal operation
(Step-down operation)
“L”: Step-down operation stopped
(All circuits deactivated)
2 VSS GND pin
3 VOUT Output voltage monitoring pin
4 EXT
Connection pin for external transistor
SOT-23-5
Top view
5
4
3
2
1
5 VIN IC power supply pin
Figure 3
Absolute Maximum Ratings
Table 4
(Ta=25 °C unless otherwise specified)
Item Symbol Absolute maximum ratings Unit
VIN pin voltage VIN A, C, E types VSS−0.3 to VSS+12 V
B, D, F types VSS−0.3 to VSS+18
VOUT pin voltage VOUT A, C, E types VSS−0.3 to VSS+12
B, D, F types VSS−0.3 to VSS+18
OFF/ON pin voltage OFF/ONV A, C, E types VSS−0.3 to VSS+12
B, D, F types VSS−0.3 to VSS+18
EXT pin voltage VEXT VSS −0.3 to VIN +0.3
EXT pin current IEXT ±50 mA
Power dissipation PD 250 mW
Operating ambient temperature Topr −40 to +85 °C
Storage temperature Tstg −40 to +125
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.
200
100
100
Power dissipation (PD)
[mW]
Temperature (Ta) [°C]
0
050 150
300
Figure 4 Power dissipation of Package (Before mounting)
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
8 Seiko Instruments Inc.
Electrical Characteristics
1. A type, B type
Table 5
(Ta=25 °C unless otherwise specified)
Parameter Symbol Condition Min. Typ. Max. Unit
Measure-
ment
circuit
Output voltage
*1
V
OUT(E)
V
OUT(S)
×
0.976
V
OUT(S)
V
OUT(S)
×
1.024 3
A type 2.5
10.0
Input voltage V
IN
B type 2.5
16.0
V
Current consumption 1 I
SS1
V
OUT
=
V
OUT(S)
×
1.2
35 60
Current consumption
during shutdown I
SSS
OFF/ONV
=
0 V
0.5
µ
A
2
EXT pin output current I
EXTH
V
EXT
=
V
IN
−
0.4 V S-8520 / 8521x15 to 24
−
2.3
−
4.5
S-8520 / 8521x25 to 34
−
3.7
−
7.0
S-8520 / 8521x35 to 44
−
5.3
−
9.3
S-8520 / 8521x45 to 54
−
6.7
−
11.3
S-8520 / 8521x55 to 60
−
8.0
−
13.3
I
EXTL
V
EXT
=
0.4 V S-8520 / 8521x15 to 24
+
4.3
+
8.4
S-8520 / 8521x25 to 34
+
7.0
+
13.2
S-8520 / 8521x35 to 44
+
9.9
+
17.5
S-8520 / 8521x45 to 54
+
12.6
+
21.4
S-8520 / 8521x55 to 60
+
15.0
+
25.1
mA
Line regulation
Δ
V
OUT1
V
OUT(S)
≤
2.0 V V
IN
=
2.5 to 2.94 V
30 60
V
OUT(S)
>
2.0 V V
IN
=
V
OUT(S)
×
1.2 to 1.4
30 60
Load regulation
Δ
V
OUT2
Load current
=
10
µ
A to I
OUT
×
1.25
30 60
mV
Output voltage temperature
coefficient
Ta
VOUT
∆
∆
Ta
=−
40 to
+
85
°
C
±
V
OUT(S)
×
5E
−
5
V /
°
C
Oscillation frequency f
osc
V
OUT(S)
≤
2.4 V 144 180 216
Measured waveform at EXT
pin. V
OUT(S)
≥
2.5 V 153 180 207 kHz
PWM / PFM control
switching duty ratio
(S-8521 Series)
PFMDuty No load, Measured waveform at EXT pin. 15 25 40 %
3
V
SH
Judged oscillation at EXT pin 1.8
ON / OFF pin
input voltage V
SL
Judged oscillation stop at EXT pin
0.3 V 2
I
SH
−
0.1
0.1
ON / OFF pin
input leakage current I
SL
−
0.1
0.1
µ
A 1
Soft start time t
ss
4.0 8.0 16.0 3
Overload detection time
(A type) t
pro
Duration from the time V
OUT
is reduced to
0 V to the time the EXT pin obtains V
IN
. 2.0 4.0 8.0 ms 2
Efficiency EFFI
93
% 3
External parts Coil: Sumida Corporation CD54 (47 µH)
Diode: Matsushita Electric Industrial Co., Ltd. MA720 (Shottky type)
Capacitor: Matsushita Electric Industrial Co., Ltd. TE (16 V, 22µF tantalum type)
Transistor: Toshiba Corporation 2SA1213Y
Base resistance (Rb): 0.68 kΩ
Base capacitor (Cb): 2200 pF (Ceramic type)
The recommended components are connected to the IC, unless otherwise indicated.
VIN=VOUT(S)×1.2 V (VIN=2.5 V if VOUT(S)≤2.0 V), IOUT=120 mA
The OFF/ON pin is connected to VIN pin.
*1. VOUT(S): Specified output voltage value, VOUT(E): Actual output voltage value
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 9
2. C type, D type
Table 6
(Ta=25 °C unless otherwise specified)
Parameter Symbol Condition Min. Typ. Max. Unit
Measure-
ment
circuit
Output voltage
*1
V
OUT(E)
V
OUT(S)
×
0.976
V
OUT(S)
V
OUT(S)
×
1.024 3
C type 2.5
10.0
Input voltage V
IN
D type 2.5
16.0
V
Current consumption 1 I
SS1
V
OUT
=
V
OUT(S)
×
1.2
10 21
Current consumption
during shutdown I
SSS
OFF/ONV
=
0 V
0.5
µ
A
2
EXT pin output current I
EXTH
V
EXT
=
V
IN
−
0.4 V S-8520 / 8521x15 to 24
−
2.3
−
4.5
S-8520 / 8521x25 to 34
−
3.7
−
7.0
S-8520 / 8521x35 to 44
−
5.3
−
9.3
S-8520 / 8521x45 to 54
−
6.7
−
11.3
S-8520 / 8521x55 to 60
−
8.0
−
13.3
I
EXTL
V
EXT
=
0.4 V S-8520 / 8521x15 to 24
+
4.3
+
8.4
S-8520 / 8521x25 to 34
+
7.0
+
13.2
S-8520 / 8521x35 to 44
+
9.9
+
17.5
S-8520 / 8521x45 to 54
+
12.6
+
21.4
S-8520 / 8521x55 to 60
+
15.0
+
25.1
mA
Line regulation
Δ
V
OUT1
V
OUT(S)
≤
2.0 V V
IN
=
2.5 to 2.94 V
30 60
V
OUT(S)
>
2.0 V V
IN
=
V
OUT(S)
×
1.2 to 1.4
30 60
Load regulation
Δ
V
OUT2
Load current
=
10
µ
A to I
OUT
×
1.25
30 60
mV
Output voltage
temperature coefficient
Ta
VOUT
∆
∆
Ta
=−
40 to
+
85
°
C
±
V
OUT(S)
×
5E
−
5
V /
°
C
Oscillation frequency f
osc
V
OUT(S)
≤
2.4 V 45 60 75
Measured waveform at
EXT pin. V
OUT(S)
≥
2.5 V 48 60 72 kHz
PWM / PFM control
switching duty ratio
(S-8521 Series)
PFMDuty No load, Measured waveform at EXT pin 15 25 40 %
3
V
SH
Judged oscillation at EXT pin 1.8
ON / OFF pin input voltage
V
SL
Judged oscillation stop at EXT pin
0.3
V 2
I
SH
−
0.1
0.1
ON / OFF pin input
leakage current I
SL
−
0.1
0.1
µ
A 1
Soft start time t
ss
6.0 12.0 24.0 3
Overload detection time
(C type) t
pro
Duration from the time V
OUT
is reduced to
0 V to the time the EXT pin obtains V
IN
. 7.0 14.0 28.0
ms 2
Efficiency EFFI
93
% 3
External parts Coil: Sumida Corporation CD54 (47 µH)
Diode: Matsushita Electric Industrial Co., Ltd. MA720 (Shottky type)
Capacitor: Matsushita Electric Industrial Co., Ltd. TE (16 V, 22µF tantalum type)
Transistor: Toshiba Corporation 2SA1213Y
Base resistance (Rb): 0.68 kΩ
Base capacitor (Cb): 2200 pF (Ceramic type)
The recommended components are connected to the IC, unless otherwise indicated.
VIN=VOUT(S)×1.2 V (VIN=2.5 V if VOUT(S)≤2.0 V), IOUT=120 mA
The OFF/ON pin is connected to VIN pin.
*1. VOUT(S): Specified output voltage value, VOUT(E): Actual output voltage value
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
10 Seiko Instruments Inc.
3. E type, F type
Table 7
(Ta=25 °C unless otherwise specified)
Parameter Symbol Condition Min. Typ. Max. Unit
Measure-
ment
circuit
Output voltage
*1
V
OUT(E)
V
OUT(S)
×
0.976
V
OUT(S)
V
OUT(S)
×
1.024 3
E type 2.5
10.0
Input voltage V
IN
F type 2.5
16.0
V
Current consumption 1 I
SS1
V
OUT
=
V
OUT(S)
×
1.2
60 100
Current consumption
during shutdown I
SSS
OFF/ONV
=
0 V
0.5
µ
A
2
EXT pin output current I
EXTH
V
EXT
=
V
IN
−
0.4 V S-8520 / 8521x15 to 24
−
2.3
−
4.5
S-8520 / 8521x25 to 34
−
3.7
−
7.0
S-8520 / 8521x35 to 44
−
5.3
−
9.3
S-8520 / 8521x45 to 54
−
6.7
−
11.3
S-8520 / 8521x55 to 60
−
8.0
−
13.3
I
EXTL
V
EXT
=
0.4 V S-8520 / 8521x15 to 24
+
4.3
+
8.4
S-8520 / 8521x25 to 34
+
7.0
+
13.2
S-8520 / 8521x35 to 44
+
9.9
+
17.5
S-8520 / 8521x45 to 54
+
12.6
+
21.4
S-8520 / 8521x55 to 60
+
15.0
+
25.1
mA
Line regulation
Δ
V
OUT1
V
OUT(S)
≤
2.0 V V
IN
=
2.5 to 2.94 V
30 60
V
OUT(S)
>
2.0 V V
IN
=
V
OUT(S)
×
1.2 to 1.4
30 60
Load regulation
Δ
V
OUT2
Load current
=
10
µ
A to I
OUT
×
1.25
30 60
mV
Output voltage temperature
coefficient
Ta
VOUT
∆
∆
Ta
=−
40 to
+
85
°
C
±
V
OUT(S)
×
5E
−
5
V /
°
C
Oscillation frequency f
osc
V
OUT(S)
≤
2.4 V 225 300 375
Measured waveform at
EXT pin. V
OUT(S)
≥
2.5 V 240 300 360 kHz
PWM / PFM control
switching duty ratio
(S-8521 Series)
PFMDuty No load, Measured waveform at EXT pin 15 25 40 %
3
V
SH
Judged oscillation at EXT pin 1.8
ON / OFF pin input voltage
V
SL
Judged oscillation stop at EXT pin
0.3
V 2
I
SH
−
0.1
0.1
ON / OFF pin input leakage
current I
SL
−
0.1
0.1
µ
A 1
Soft start time t
ss
2.0 4.5 9.2 3
Overload detection time
(E type) t
pro
Duration from the time V
OUT
is reduced to
0 V to the time the EXT pin obtains V
IN
. 1.3 2.6 4.5
ms 2
Efficiency EFFI
90
% 3
External parts Coil: Sumida Corporation CD54 (47 µH)
Diode: Matsushita Electric Industrial Co., Ltd. MA720 (Shottky type)
Capacitor: Matsushita Electric Industrial Co., Ltd. TE (16 V, 22µF tantalum type)
Transistor: Toshiba Corporation 2SA1213Y
Base resistance (Rb): 0.68 kΩ
Base capacitor (Cb): 2200 pF (Ceramic type)
The recommended components are connected to the IC, unless otherwise indicated.
VIN=VOUT(S)×1.2 V (VIN=2.5 V if VOUT(S)≤2.0 V), IOUT=120 mA
The OFF/ON pin is connected to VIN pin.
*1. VOUT(S): Specified output voltage value, VOUT(E): Actual output voltage value
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 11
Measurement Circuits
1.
EXT
VSS
OFF/ON
VOUT open
open
VIN
A
Figure 5
2.
VSS
OFF/ON
VIN
−
+
VOUT
EXT
Oscillosco
p
e
A
Figure 6
3.
VSS
OFF/ON
0.68 kΩ2200 pF
VIN
− V
+
VOUT
EXT
−
+
Figure 7
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
12 Seiko Instruments Inc.
Operation
1. Switching control method
1. 1 PWM control (S-8520 Series)
The S-8520 Series consists of DC-DC converters that employ a pulse-width modulation (PWM)
system. This series is characterized by its low current consumption. In conventional PFM system
DC-DC converters, pulses are skipped when they are operated with a low output load current, causing
variations in the ripple frequency of the output voltage and an increase in the ripple voltage. Both of
these effects constitute inherent drawbacks to those converters.
In the S-8520 series the pulse width varies in the range from 0 to 100% according to the load current,
yet ripple voltage produced by the switching can easily be removed by a filter since the switching
frequency is always constant. These converters thus provide a low-ripple voltage over wide range of
input voltage and load current. And it will be skippped to be low current consumption when the pulse
width is 0% or it is no load, input current voltage is high.
1. 2 PWM / PFM switching control (S-8521 Series)
The S-8521 series is a DC-DC converter that automatically switches between a pulse width
modulation method (PWM) and a pulse frequency modulation method (PFM), depending on the load
current, and features low current consumption.
The S-8521 series operates under PWM control with the pulse width duty changing from 25 to 100%
when the output load current is high. On the other hand, when the output current is low, the S-8541
series operates under PFM control with the pulse width duty fixed at 25%, and pulses are skipped
according to the load current. The oscillator thus oscillates intermittently so that the resultant lower
current consumption prevents a reduction in the efficiency when the load current is low. The
switching point from PWM control to PFM control depends on the external devices (coil, diode, etc.),
input voltage, and output voltage. This series is an especially efficient DC-DC converter at an output
current of around 100 µA.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 13
2. Soft start function
The S-8520 / 8521 Series comes with a built-in soft start circuit. This circuit enables the output voltage
(VOUT) to rise gradually over the specified soft start time (t), when the power is switched on or when the
OFF/ON pin remains at the "H" level. This prevents the output voltage from overshooting.
However, the soft start function of this IC is not able to perfectly prevent a rush current from flowing to the
load (Refer to Figure 8). Since this rush current depends on the input voltage and load conditions, we
recommend that you evaluate it by testing performance with the actual equipment.
S-8520A33MC (VIN: 0→4.0 V)
t [1 ms/div]
VOUT
[1 V/div]
Rush current
[0.5 A/div]
0 A
1.5 A
3 V Power switched on
0 V
Figure 8 Waveforms of output voltage and rush current at soft start
3. OFFON/ pin (Shutdown pin)
This pin deactivates or activates the step-down operation.
When the OFF/ON pin is set to "L", the VIN voltage appears through the EXT pin, prodding the
switching transistor to go off. All the internal circuits stop working, and substantial savings in current
consumption are thus achieved.
The OFF/ON pin is configured as shown in Figure 9. Since pull-up or pull-down is not performed
internally, please avoid operating the pin in a floating state. Also, try to refrain from applying a voltage of
0.3 to 1.8 V to the pin, lest the current consumption increase. When this OFF/ON pin is not used,
leave it coupled to the VIN pin.
Table 8
OFF/ON pin CR Oscillation Circuit Output Voltage
“H” Activated Set value
“L” Deactivated VSS
OFF/ON
VIN
VSS
Figure 9
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
14 Seiko Instruments Inc.
4. Overload protection circuit (A, C, E types)
The A, C and E types of the S-8520 / 8521 Series come with a built-in overload protection circuit.
If the output voltage falls because of an overload, the maximum duty state (100%) will continue. If this
100% duty state lasts longer than the prescribed overload detection time (tpro), the overload protection
circuit will hold the EXT pin at "H," thereby protecting the switching transistor and inductor. When the
overload protection circuit is functioning, the reference voltage circuit will be activated by means of a soft
start in the IC, and the reference voltage will rise slowly from 0 V. The reference voltage and the
feedback voltage obtained by dividing the output voltage are compared to each other. So long as the
reference voltage is lower, the EXT pin will be held at "H" to keep the oscillation inactive. If the
reference voltage keeps rising and exceeds the feedback voltage, the oscillation will resume.
If the load is heavy when the oscillation is restarted, and the EXT pin holds the "L" level longer than the
specified overload detection time (tpro), the overload protection circuit will operate again, and the IC will
enter intermittent operation mode, in which it repeats the actions described above. Once the overload
state is eliminated, the IC resumes normal operation.
Waveforms
at EXT pin
Protection circuit ON
[tss×0.3]
Overload detection time (tpro)
Figure 10 Waveforms appearing at EXT pin as the overload protection circuit operates
5. 100% duty cycle
The S-8520 / 8521 Series operates with a maximum duty cycle of 100%. When a B, D and F types
products not provided with an overload protection circuit is used, the switching transistor can be kept ON
to supply current to the load continually, even in cases where the input voltage falls below the preset
output voltage value. The output voltage delivered under these circumstances is one that results from
subtracting, from the input voltage, the voltage drop caused by the DC resistance of the inductance and
the on-resistance of the switching transistor.
If an A, C and E types products provided with an overload protection circuit is used, this protection circuit
will function when the 100% duty state has lasted longer than the preset overload detection time (tpro),
causing the IC to enter intermittent operation mode. Under these conditions, the IC will not be able to
supply current to the load continually, unlike the case described in the preceding paragraph.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 15
Selection of Series Products and Associated External Components
1. Method for selecting series products
The S-8520 / 8521 Series is classified into 12 types, according to the way the control systems (PWM
control and PWM / PFM Switching control), the different oscillation frequencies, and the inclusion or
exclusion of an overload protection circuit are combined one with another. Please select the type that
best suits your needs by taking advantage of the features of each type described below.
1. 1 Control systems
Two different control systems are available: PWM control system (S-8520 Series) and PWM / PFM
switching control system (S-8521 Series).
If particular importance is attached to the operation efficiency while the load is on standby -- for
example, in an application where the load current heavily varies from that in standby state as the load
starts operating -- a high efficiency will be obtained in standby mode by selecting the PWM / PFM
switching control system (S-8521 Series).
Moreover, for applications where switching noise poses a serious problem, the PWM control system
(S-8520 Series), in which the switching frequency does not vary with the load current, is preferable
because it can eliminate ripple voltages easily using a filter.
1. 2 Oscillation frequencies
The oscillation frequencies are selectable in 180 kHz (A and B types), 60 kHz (C, D types), and 300
kHz (E, F types).
Because of their high oscillation frequency and low ripple voltage the A, B, E and F types offer
excellent transient response characteristics. The products in these series allow the use of small-
sized inductors since the peak current remains smaller in the same load current than with products of
the other series. In addition, they can also be used with small output capacitors. These outstanding
features make the A, B, E and F types ideal products for downsizing the associated equipment.
On the other hand, the C and D types, having a lower oscillation frequency, are characterized by a
small self-consumption of current and excellent efficiency under light loads. In particular, the D type,
which employs a PWM / PFM switching control system, enables the operation efficiency to be
improved drastically when the output load current is approximately 100 µA (Refer to “Reference
Data”).
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
16 Seiko Instruments Inc.
1. 3 Overload protection circuit
Products can be chosen either with an overload protection circuit (A, C, E types) or without one (B, D,
F types).
Products with an overload protection circuit (A, C, E types) enter intermittent operation mode when the
overload protection circuit operates to accommodate overloads or load short-circuiting. This
protects the switching elements and inductors. Nonetheless, in an application where the load needs to
be fed continually with a current by taking advantage of the 100 % duty cycle state, even if the input
voltage falls below the output voltage value, a B, D, F types product will have to be used. Choose
whichever product best handles the conditions of your application.
In making the selection, please keep in mind that the upper limit of the operating voltage range is
either 10 V (A, C, E types) or 16 V (B, D, F types), depending on whether the product comes with an
overload protection circuit built in.
Table 9 provides a rough guide for selecting a product type depending on the requirements of the
application. Choose the product that gives you the largest number of circles ().
Table 9
S-8520 Series S-8521 Series
A B C D E F A B C D E F
An overload protection circuit is required
The input voltage range exceeds 10 V
The efficiency under light loads (load
current≤1 mA) is an important factor
To be operated with a medium load
current (200 mA class)
To be operated with a high load current
(1 A class)
It is important to have a low-ripple voltage
Importance is attached to the downsizing
of external components
Remark : Indispensable condition
: Superiority of requirement
: Particularly superiority of requirement
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 17
2. Inductor
The inductance value (L) greatly affects the maximum output current (IOUT) and the efficiency (η).
The peak current (IPK) increases by decreasing L and the stability of the circuit improves and IOUT
increases. If L is made even smaller, the efficiency falls causing a decline in the current drive capacity
for the switching transistor, and IOUT decreases.
The loss of IPK by the switching transistor decreases by increasing L and the efficiency becomes
maximum at a certain L value. Increasing L further decreases the efficiency due to the loss of coil DC
resistance. IOUT also decreases.
When the inductance is large in an S-8520 / 8521 series product, the output voltage may grow unstable in
some cases, depending on the conditions of the input voltage, output voltage, and the load current.
Perform sufficient evaluation under the actual condition and decide an optimum inductance.
The recommended inductances are 47 µH for A, B, C, D types and 22 µH for E, F types.
When choosing an inductor, attention to its allowable current should be paid since the current over the
allowable value will cause magnetic saturation in the inductor, leading to a marked decline in efficiency.
An inductor should therefore be selected so as not IPK to surpass its allowable current. The peak current
(IPK) is represented by the following equation in non-continuous operation mode:
)VV(Lf2
)VV()VV(
II
FINosc
OUTINFOUT
OUTPK +×××
−×+
+=
Where fosc is the oscillation frequency, and VF the forward voltage of the diode.
3. Diode
The diode to be externally coupled to the IC should be a type that meets the following conditions:
• Its forward voltage is low (Schottky barrier diode recommended).
• Its switching speed is high (50 ns max.).
• Its reverse direction voltage is higher than VIN.
• Its current rating is higher than IPK.
4. Capacitors (CIN, COUT)
The capacitor inserted on the input side (CIN) serves to lower the power impedance and to average the
input current for better efficiency. Select the CIN value according to the impedance of the power
supplied. As a rough rule of thumb, you should use a value of 47 to 100 µF, although the actual value
will depend on the impedance of the power in use and the load current value.
For the output side capacitor (COUT), select one of large capacitance with low ESR (Equivalent Series
Resistance) for smoothing the ripple voltage. However, notice that a capacitor with extremely low ESR
(say, below 0.3 Ω), such as a ceramic capacitor, could make the output voltage unstable, depending on
the input voltage and load current conditions. Instead, a tantalum electrolytic capacitor is recommended.
A capacitance value from 47 to 100 µF can serve as a rough yardstick for this selection.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
18 Seiko Instruments Inc.
5. External transistor
The external transistor of the enhancement (Pch) MOS FET type or bipolar (PNP) typ.
5. 1 Enhancement (Pch) MOS FET type
The EXT pin is capable of directly driving a Pch MOS FET with a gate capacity of some 1000 pF.
When a Pch MOS FET is chosen, because it has a higher switching speed than a PNP type bipolar
transistor and because power losses due to the presence of a base current are avoided, efficiency will
be 2 to 3 % higher than when other types of transistor are employed.
The important parameters to be kept in mind in selecting a MOS FET include the threshold voltage,
breakdown voltage between gate and source, breakdown voltage between drain and source, total
gate capacity, on-resistance, and the current rating.
The EXT pin swings from voltage VIN over to voltage VSS. If the input voltage is low, a MOS FET with
a low threshold voltage has to be used so that the MOS FET will come on as required. If, conversely,
the input voltage is high, select a MOS FET whose gate-source breakdown voltage is higher than the
input voltage by at least several volts.
Immediately after the power is turned on, or when the power is turned off (that is, when the step-down
operation is terminated), the input voltage will be imposed across the drain and the source of the MOS
FET. Therefore, the transistor needs to have a drain-source breakdown voltage that is also several
volts higher than the input voltage.
The total gate capacity and the on-resistance affect the efficiency.
The power loss for charging and discharging the gate capacity by switching operation will increase,
when the total gate capacity becomes larger and the input voltage rises higher. Therefore the gate
capacity affects the efficiency of power in a low load current region. If the efficiency under light loads
is a matter of particular concern, select a MOS FET with a small total gate capacity.
In regions where the load current is high, the efficiency is affected by power losses caused due to the
on-resistance of the MOS FET. Therefore, if the efficiency under heavy loads is particularly
important for your application, choose a MOS FET with as low an on-resistance as possible.
As for the current rating, select a MOS FET whose maximum continuous drain current rating is higher
than IPK.
For reference purpose, some efficiency data has been included in this document. For applications
with an input voltage range of 10 V or less, data was obtained by using TM6201 of Toyoda Industries
Corporation. IRF7606, a standard of International Rectifier Corporation, was used for applications
with an input voltage range over 10 V (Refer to "Reference Data").
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 19
5. 2 Bipolar PNP type
Figure 11 shows a sample circuit diagram using Toshiba Corporation 2SA1213-Y for the bipolar
transistor (PNP). The driving capacity for increasing the output current by means of a bipolar
transistor is determined by the hFE value and the Rb value of that bipolar transistor.
VIN
EXT
VIN
RbCb
Toshiba Corporation
2SA1213-Y
Figure 11
The Rb-value is given by the following equation:
EXTLb
IN
bI
4.0
I
7.0V
R−
−
=
Find the necessary base current (Ib) using the (hFE) value of bipolar transistor by the equation,
FE
PK
bh
I
I=, and select a smaller Rb value.
A small Rb value will certainly contribute to increasing the output current, but it will also adversely
affect the efficiency. Moreover, in practice, a current may flow as the pulses or a voltage drop may
take place due to the wiring resistance or some other reason. Determine an optimum value through
experimentation.
In addition, if speed-up capacitor (Cb) is inserted in parallel with resistance Rb, as shown in Figure 11,
the switching loss will be reduced, leading to a higher efficiency.
Select a Cb value by using the following equation as a guide:
7.0fR2
1
C
oscb
b×××π
≤
Select a Cb value after performing sufficient evaluation since the optimum Cb value differs depending
upon the characteristics of the bipolar transistor.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
20 Seiko Instruments Inc.
Standard Circuits
1. Using a bipolar transistor
VSS
VOUT
+
VIN
CIN
L
SD COUT
OFF/ON
Reference voltage
source with soft start
VIN
T
r
Cb Rb
EXT
OFF/ONV
+
+
−
PWM control or
PWM/PFM switching
cotrol circuit
Oscillation
circuit
Figure 12
2. Using a Pch MOS FET transistor
VSS
VOUT
L
SD COUT
+
+
−
VIN
T
r
+
EXT
VIN
CIN
OFF/ON OFF/ONV
Oscillation
circuit
Reference voltage
source with soft start
PWM control or
PWM/PFM switching
control circuit
Figure 13
Caution The above connection diagram and constant will not guarantees successful operation.
Perform through evaluation using the actual application to set the constant.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 21
Precautions
• Mount the external capacitors, the diode and the coil as close as possible to the IC, and secure grounding
at a single location.
• Characteristics ripple voltage and spike noise occur in IC containing switching regulators. Moreover, rush
current flows at the time of a power supply injection. Because these largely depend on the coil, the
capacitor and impedance of power supply used, fully check them using an actually mounted model.
• The overload protection circuit of this IC performs the protective function by detecting the maximum duty
time (100 %). In choosing the components, make sure that over currents generated by short-circuits in
the load, etc., will not surpass the allowable dissipation of the switching transistor and inductor.
• Make sure that dissipation of the switching transistor (especially at a high temperature) does not exceed
the allowable dissipation of the package.
• Do not apply an electrostatic discharge to this IC that exceeds the performance ratings of the built-in
electrostatic protection circuit.
• SII claims no responsibility for any and all disputes arising out of or in connection with any infringement of
the products including this IC upon patents owned by a third party.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
22 Seiko Instruments Inc.
Application Circuits
1. External adjustment of output voltage
The S-8520 / 8521 Series allows you to adjust the output voltage or to set the output voltage to a value
over the preset output voltage range (6 V) of the products of this series, when external resistances (RA
and RB), and capacitor (CC) are added, as illustrated in Figure 14. Moreover, a temperature gradient
can be obtained by inserting a thermistor or other element in series with RA and RB.
S-8520/8521Series
CC RA
RB
D1
VOUT
−
+
VIN
OUT
EXT
−
+
Reference
voltage source
with soft start
+
−
R2
R1
OFF/ON
VSS
Oscillation
circuit
PWM control or
PWM/PFM switching
control circuit
Figure 14
Caution The above connection diagram and constant will not guarantees successful operation.
Perform through evaluation using the actual application to set the constant.
The S-8520 / 8521 Series have an internal impedance of R1 and R2 between the VOUT pin and the VSS
pin, as shown in Figure 14.
Therefore, OUT (the output voltage) is determined by the output voltage value (VOUT) of the S-8520 / 8521
Series, and the ratio of the parallel resistance value of external resistance (RB) and internal resistances
(R1+R2) of the IC, to external resistance (RA). The output voltage is expressed by the following equation:
OUT=VOUT+VOUT×RA÷(RB//*1(R1 + R2))
The voltage accuracy of the OUT set by resistances (RA and RB) is not only affected by the IC's output
voltage accuracy (VOUT ±2.4 %), but also by the absolute precision of external resistances (RA and RB) in
use and the absolute value deviations of internal resistances (R1 and R2) in the IC.
Let us designate the maximum deviations of the absolute value of RA and RB by RAmax and RBmax,
respectively, the minimum deviations by RAmin and RBmin, respectively, and the maximum and minimum
deviations of the absolute value of R1 and R2 in the IC by (R1+R2) max and (R1+R2) min, respectively.
Then, the minimum deviation value OUTmin and the maximum deviation value OUTmax of the OUT are
expressed by the following equations:
OUT min.=VOUT×0.976+VOUT×0.976×RAmin.÷(RBmax//(R1+R2) max.)
OUT max.=VOUT×1.024+VOUT×1.024×RAmax.÷(RBmin//(R1+R2) min.)
The voltage accuracy of the OUT cannot be made higher than the output voltage accuracy (VOUT ±2.4 %) of
the IC itself, without adjusting the RA and RB involved. The closer the voltage value of the output OUT and
the output voltage value (VOUT) of the IC are brought to one other, the more the output voltage remains
immune to deviations in the absolute accuracy of RA and RB and the absolute value of R1 and R2 in the IC. In
particular, to suppress the influence of deviations in R1 and R2 in the IC, a major contributor to deviations in
the OUT, the RA and RB must be limited to a much smaller value than that of R1 and R2 in the IC.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 23
On the other hand, a reactive current flows through RA and RB. This reactive current must be reduced to a
negligible value with respect to the load current in the actual use of the IC so that the efficiency characteristics
will not be degraded. This requires that the value of RA and RB be made sufficiently large.
However, too large a value (more than 1 MΩ) for the RA and RB would make the IC vulnerable to external noise.
Check the influence of this value on actual equipment.
There is a tradeoff between the voltage accuracy of the OUT and the reactive current. This should be taken
into consideration based on the requirements of the intended application.
Deviations in the absolute value of the internal resistances (R1 and R2) in the IC vary with the output voltage of
the S-8520 / 8521 Series, and are broadly classified as follows:
Table 10
Output voltage Deviations in the absolute value of R1 and R2 in the IC
1.5 V to 2.0 V 5.16 MΩ to 28.9 MΩ
2.1 V to 2.5 V 4.44 MΩ to 27.0 MΩ
2.6 V to 3.3 V 3.60 MΩ to 23.3 MΩ
3.4 V to 4.9 V 2.44 MΩ to 19.5 MΩ
5.0 V to 6.0 V 2.45 MΩ to 15.6 MΩ
When a value of R1+R2 given by the equation indicated below is taken in calculating the voltage value of
the output OUT, a median voltage deviation will be obtained for the OUT.
R1+R2=2÷(1÷maximum deviation in absolute value of R1 and R2+1÷minimum deviation in absolute value
of R1 and R2)
Moreover, add a capacitor (CC) in parallel to the external resistance (RA) in order to avoid output
oscillations and other types of instability. (Refer to Figure 14.)
Make sure that CC is larger than the value given by the following equation:
CC (F)≥1÷(2×π×RA (Ω)×7.5 kHz)
If a large CC value is selected, a longer soft start time than the one set up in the IC will be set.
• SII is equipped with a tool that allows you to automatically calculate the necessary resistance values of
RA and RB from the required voltage accuracy of the OUT. SII will be pleased to assist its customers in
determining the RA and RB values. Should such assistance be desired, please inquire.
• Moreover, SII also has ample information on which peripheral components are suitable for use with this
IC and data concerning the deviations in the IC's characteristics. We are ready to help our customers
with the design of application circuits. Please contact the SII Components Sales Dept.
*1. // shows the combined resistance in parallel.
Caution The above connection diagram and constant will not guarantees successful operation.
Perform through evaluation using the actual application to set the constant.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
24 Seiko Instruments Inc.
Typical Characteristics
1. Examples of major parameters characteristics
(1) Current consumption (ISS1)-Input voltage (VIN)
0
5
10
15
20
Ta=25°C
Ta=85°C
I
SS1
[µA]
(f
osc
=60 kHz
)
2 4 6 8 10 12 14 16
V
IN
[V]
Ta=−40°C
0
10
20
30
40
2 4 6 8 10 12 14 16
VIN [V]
ISS1 [µA]
Ta=−40°C
Ta=85°C
Ta=25°C
(fosc=180 kHz)
0
10
20
30
40
50
60
2 4 6 8 10 12 14 16
V
IN
[V]
I
SS1
[µA]
(f
osc
=300 kHz)
Ta=−40°C Ta=25°
Ta=85°C
(2) Oscillation frequency (fosc)-Input voltage (VIN)
40
45
50
55
60
65
70
75
80
2 4 6 8 10 12 14 16
VIN [V]
fosc [kHz]
(fosc=60 kHz)
Ta=25°C
Ta=85°C
Ta=−40°C
140
150
160
170
180
190
200
210
220
2 4 6 8 10 12 14 16
VIN [V]
fosc [kHz]
(
fosc=180 kHz
)
Ta=25°C
Ta=85°C
Ta=−40°C
240
260
280
300
320
340
360
2 4 6 8 10 12 14 16
VIN [V]
fosc [kHz]
(fosc=300 kHz)
Ta=−40°
Ta=25°C
Ta=85°C
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 25
(3) EXT pin output current “H” (IEXTH)-Input voltage (VIN)(4) EXT pin output current “L” (IEXTL)-Input voltage (VIN)
2 4 6 8 10 12 14 16
VIN [V]
IEXTH [mA]
Ta=−40°C
Ta=85°C
Ta=25°C
−60
−50
−40
−30
−20
−10
0
0
10
20
30
40
50
60
2 4 6 8 10 12 14 16
VIN [V]
IEXTL [mA]
Ta=−40°C
Ta=85°C
Ta=25°C
(5) Soft start time (tSS)-Input voltage (VIN)
0
5
10
15
20
25
2 4 6 8 10 12 14 16
VIN [V]
tSS [ms]
(fosc=60 kHz)
Ta=−40°C
Ta=85°C
Ta=25°C
0
5
10
15
20
25
2 4 6 8 10 12 14 16
VIN [V]
tSS [ms]
(fosc=180 kHz)
Ta=−40°C
Ta=85°C
Ta=25°C
0
2
4
6
8
10
2 4 6 8 10 12 14 16
VIN [V]
t
SS
[
ms
]
(fosc=300 kHz)
Ta=25°C
Ta=85°C
Ta=−40°C
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
26 Seiko Instruments Inc.
(6) Overload detection time (tpro)- Input voltage (VIN)
6
10
14
18
22
26
30
2 4 6 8 10 12 14 16
(fosc=60 kHz)
t
p
ro [ms]
Ta=−40°C
VIN [V]
Ta=25°C
Ta=85°C
2
3
4
5
6
7
8
2 4 6 8 10 12 14 16
VIN [V]
tpro [ms]
Ta=−40°C
Ta=85°C
Ta=25°C
(fosc=180 kHz)
1
2
3
4
2 4 6 8 10 12 14 16
VIN [V]
t
p
ro [ms]
(fosc=300 kHz)
Ta=85°C
Ta=25°C
Ta=−40°C
(7) OFFON/ pin input voltage “H” (VSH)-Input voltage
(VIN)
(8) OFFON/ pin input voltage “L” (VSL)-Input voltage
(VIN)
0.4
0.6
0.8
1.0
1.2
1.4
1.6
1.8
2 4 6 8 10 12 14 16
VIN [V]
VSH [V]
Ta=−40°C
Ta=25°C
Ta=85°C
0.3
0.5
0.7
0.9
1.1
1.3
1.5
1.7
2 4 6 8 10 12 14 16
VIN [V]
VSL [V]
Ta=−40°C
Ta=85°C
Ta=25°C
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 27
(9) Output voltage (VOUT)-Input voltage(VIN)
S-8521B30MC S-8521B50MC
(
Ta=25°C
)
2.98
2.99
3.00
3.01
3.02
3.03
3.04
3.05
3.06
3.07
3.08
2 4 6 8 10 12 14 16
VIN [V]
VOUT [V]
IOUT=100 mA
IOUT=500 mA
IOUT=0.1 mA
(
Ta=25°C
)
4.98
4.99
5.00
5.01
5.02
5.03
5.04
5.05
5.06
5.07
5.08
2 4 6 8 10 12 14 16
VIN [V]
VOUT [V]
IOUT=100 mA
IOUT=500 mA
IOUT=0.1 mA
S-8521F33MC S-8521F50MC
(
Ta=25°C
)
3.28
3.29
3.30
3.31
3.32
3.33
3.34
3.35
3.36
3.37
3.38
2 4 6 8 10 12 14 16
VIN [V]
VOUT [V]
IOUT=0.1 mA
IOUT=100 mA
IOUT=500 mA
(
Ta=25°C
)
4.97
4.98
4.99
5.00
5.01
5.02
5.03
5.04
5.05
5.06
5.07
2 4 6 8 10 12 14 16
VIN [V]
VOUT [V]
IOUT=0.1 mA
IOUT=100 mA
IOUT=500 mA
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
28 Seiko Instruments Inc.
2. Transient Response Characteristics
2. 1 Power-on (IOUT: no load)
(1) S-8520 / 8521C30MC
(VIN=0→3.6 V)
t [2 ms/div]
VIN
[2.5 V/div]
VOUT
[1 V/div]
0 V
3 V
0 V
10 V
(VIN=0→9.0 V)
t [2 ms/div]
VIN
[2.5 V/div]
VOUT
[1 V/div]
0 V
3 V
0 V
10 V
(2) S-8520 / 8521A30MC
(VIN=0→3.6 V)
t [1 ms/div]
VIN
[2.5 V/div]
VOUT
[1 V/div]
0 V
3 V
0 V
10 V
(VIN=0→9.0 V)
t [1 ms/div]
VIN
[2.5 V/div]
VOUT
[1 V/div)]
0 V
3 V
0 V
10 V
(3) S-8520 / 8521E33MC
(VIN=0→4.0 V)
t [1 ms/div]
VIN
[2.5 V/div]
VOUT
[1 V/div]
0 V
3 V
0 V
10 V
(VIN=0→9.0 V)
t [1 ms/div]
VIN
[2.5 V/div]
VOUT
[1 V/div]
0 V
3 V
0 V
10 V
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 29
2. 2 Shutdown pin response ( OFFON/V=0→1.8 V, IOUT=No load)
(1) S-8520 / 8521C30MC
(VIN=3.6 V)
t [2 ms/div]
OFF/ONV
[1 V/div]
VOUT
[1 V/div]
0 V
3 V
0 V
3 V
(VIN=9.0 V)
t [2 ms/div]
VOUT
[1 V/div]
0 V
3 V
0 V
3 V
OFF/ONV
[1 V/div]
(2) S-8520 / 8521A30MC
(VIN=3.6 V)
t [1 ms/div]
VOUT
[1 V/div]
0 V
3 V
0 V
3 V
OFF/ONV
[1 V/div]
(VIN=9.0 V)
t [1 ms/div]
VOUT
[1 V/div]
0 V
3 V
0 V
3 V
OFF/ONV
[1 V/div]
(3) S-8520 / 8521E33MC
(VIN=4.0 V)
t [1 ms/div]
VOUT
[1 V/div]
0 V
3 V
0 V
3 V
OFF/ONV
[1 V/div]
(VIN=9.0 V)
t [1 ms/div]
VOUT
[1 V/div]
0 V
3 V
0 V
3 V
OFF/ONV
[1 V/div]
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
30 Seiko Instruments Inc.
2. 3 Supply voltage variation (VIN=4→9 V, 9→4 V)
(1) S-8520 / 8521C30MC
(IOUT=10 mA)
t [0.5 ms/div]
VIN
[2.5 V/div]
VOUT
[0.2 V/div]
0 V
10 V
(IOUT=500 mA)
t
[
0.5 ms/div
]
VIN
[2.5 V/div]
VOUT
[0.2 V/div]
0 V
10 V
(2) S-8520 / 8521A30MC
(IOUT=10mA)
t [0.5 ms/div]
VIN
[2.5 V/div]
VOUT
[0.2 V/div]
0 V
10 V
(IOUT=500 mA)
t
[
0.5 ms/div
]
VIN
[2.5 V/div]
VOUT
[0.2 V/div]
0 V
10 V
(3) S-8520 / 8521E33MC
(IOUT=10 mA)
t [0.5 ms/div]
VIN
[2.5 V/div]
VOUT
[0.2 V/div]
0 V
10 V
(IOUT=500 mA)
t
[
0.5 ms/div
]
VIN
[2.5 V/div]
VOUT
[0.2 V/div]
0 V
10 V
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 31
2. 4 Load variation
(1) S-8520 / 8521C30MC
(
VIN=3.6 V, IOUT=0.1→500 mA
)
t [0.1 ms/div]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
(VIN=3.6 V, IOUT=500→0.1 mA)
t [5 ms/div]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
(2) S-8520 / 8521A30MC
(VIN=3.6 V, IOUT=0.1→500 mA)
t [0.1 ms/div]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
(VIN=3.6 V, IOUT=500→0.1 mA)
t [10 ms/div]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
(3) S-8520 / 8521E33MC
(VIN=4.0 V, IOUT=0.1→500 mA)
t
[
0.1 ms/div
)
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
(VIN=4.0 V, IOUT=500→0.1 mA
)
t
[
5 ms/div
]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
32 Seiko Instruments Inc.
Reference Data
This reference data is intended to help you select peripheral components to be externally connected to the
IC. Therefore, this information provides recommendations on external components selected with a view to
accommodating a wide variety of IC applications. Characteristic data is duly indicated in the table below.
Table 11 External parts for efficiency data
Product name Output
voltage Inductor Transistor Diode
Output
capacitor Application
S-8520B30MC 3.0 V CD105 / 47
µ
H MA737 47
µ
F I
OUT
≤
1 A, V
IN
≤
10 V
S-8520F33MC D62F / 22
µ
H TM6201 MA720 I
OUT
≤
0.5 A, V
IN
≤
10 V
S-8520F33MC 3.3 V CDH113 / 22
µ
H IRF7606 MA737 22
µ
F I
OUT
≤
1 A, V
IN
≤
16 V
S-8521D30MC TM6201
I
OUT
≤
0.5 A, V
IN
≤
10 V,
With e
quipment standby mode
S-8521D30MC
CD54 / 47
µ
F
IRF7606
MA720 47
µ
F×2 I
OUT
≤
0.5 A, V
IN
≤
16 V,
With e
quipment standby mode
S-8521B30MC TM6201
I
OUT
≤
1 A, V
IN
≤
10 V,
With e
quipment standby mode
S-8521B30MC
3.0 V
CD105 / 47
µ
H
IRF7606
MA737 47
µ
F I
OUT
≤
1 A, V
IN
≤
16 V,
With e
quipment standby mode
S-8521F33MC D62F / 22
µ
H TM6201 MA720 I
OUT
≤
0.5 A, V
IN
≤
10 V,
With e
quipment standby mode
S-8521F33MC
3.3 V CDH113 / 22
µ
H IRF7606 MA737
22
µ
F I
OUT
≤
1 A, V
IN
≤
16 V,
With e
quipment standby mode
S-8520B50MC CD54 / 47
µ
F TM6201 MA720 I
OUT
≤
0.5 A, V
IN
≤
10 V
S-8520B50MC CD105 / 47
µ
H IRF7606 MA737 47
µ
F I
OUT
≤
1 A, V
IN
≤
16 V
S-8520F50MC D62F / 22
µ
H TM6201 MA720 I
OUT
≤
0.5 A, V
IN
≤
10 V
S-8520F50MC CDH113 / 22
µ
H IRF7606 MA737 22
µ
F I
OUT
≤
1 A, V
IN
≤
16 V
S-8521D50MC CD54 / 47
µ
F TM6201 MA720 I
OUT
≤
0.5 A, V
IN
≤
10 V,
With e
quipment standby mode
S-8521D50MC CD105 / 47
µ
H IRF7606 MA737
47
µ
F×2 I
OUT
≤
1 A, V
IN
≤
16 V,
With e
quipment standby mode
S-8521B50MC CD54 / 47
µ
F TM6201 MA720 I
OUT
≤
0.5 A, V
IN
≤
10 V,
With e
quipment standby mode
S-8521B50MC CD105 / 47
µ
H IRF7606 MA737
47
µ
F I
OUT
≤
1 A, V
IN
≤
16 V,
With e
quipment standby mode
S-8521F50MC D62F / 22
µ
H TM6201 MA720 I
OUT
≤
0.5 A, V
IN
≤
10 V,
With e
quipment standby mode
S-8521F50MC
5.0 V
CDH113 / 22
µ
H IRF7606 MA737
22
µ
F I
OUT
≤
1 A, V
IN
≤
16 V,
With e
quipment standby mode
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 33
Table 12 External parts for Ripple data
Product name Output
voltage Inductor Transistor R
b
C
b
Diode
Output
capacitor
S-8520D30MC
S-8521D30MC 47
µ
F×2
S-8520B30MC
S-8521B30MC
3.0 V CD105 / 47
µ
H 2SA1213Y 680
Ω
2200 pF MA720
22
µ
F×2
S-8520F33MC
S-8521F33MC 3.3 V CDH113 / 22
µ
H IRF7606
MA737 22
µ
F
S-8520D50MC
S-8521D50MC 47
µ
F×2
S-8520B50MC
S-8521B50MC
CD105 / 47
µ
H 2SA1213Y 680
Ω
2200 pF MA720
22
µ
F×2
S-8520F50MC
S-8521F50MC
5.0 V
CDH113 / 22
µ
H IRF7606
MA737 22
µ
F
Table 13 Performance Data
Component Product name
Manufacturer name
“L” value DC resistance
Maximum
allowable
current
Diameter Height
Inductor CD54 0.37
Ω
0.72 A 5.8 mm 4.5 mm
CD105 47
µ
H 0.17
Ω
1.28 A 10.0 mm 5.4 mm
CDH113
Sumida Corporation
0.09
Ω
1.44 A 11.0 mm 3.7 mm
D62F Toko Ink.
22
µ
H 0.25
Ω
0.70 A 6.0 mm 2.7 mm
Diode MA720 Forward current
500 mA (at V
F
=
0.55 V)
MA737
Matsushita Electric
Industrial Co., Ltd. Forward current
1.5 A (at V
F
=
0.5 V)
Output capacity F93 Nichicon Corporation
TE
Matsushita Electric
Industrial Co., Ltd.
External
transistor
(Bipolar PNP)
2SA1213Y Toshiba Corporation V
CEO
50 V max., I
C
−
2 A max., h
FE
120 to 240,
SOT-89-3 package
External
transistor
(MOS FET)
TM6201 Toyota Industries
Corporation
V
GS
12 V max., I
D
−
2 A max., V
th
−
0.7 V min.,
C
iss
320 pF typ., R
on
0.25
Ω
max. (V
GS
=−
4.5 V),
SOT-89-3 package
IRF7606
International Rectifier
Corporation
V
GS
20 V max., I
D
−
2.4 A max., V
th
−
1 V min.,
C
iss
470 pF typ., R
on
0.15
Ω
max. (V
GS
=−
4.5 V),
Micro 8 package
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
34 Seiko Instruments Inc.
1. Efficiency Characteristics: Output current (IOUT)-Efficiency (EFFI)
(1) S-8520B30MC
(CD105/47
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=3.6 V
VIN=9.0 V
(2) S-8520F33MC
(D62F/22
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=9 V
VIN=6 V
VIN=4 V
(CDH113/22
µ
H, IRF7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=14 V
VIN=9 V
VIN=6 V
VIN=4 V
(3) S-8521D30MC
(CD54/47
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=3.6 V
VIN=9.0 V
(CD54/47
µ
H, IRF7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=3.6 V
VIN=9.0 V
(4) S-8521B30MC
(CD105/47
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=3.6 V
VIN=9.0 V
(CD105/47
µ
H, IFR7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=3.6 V
VIN=9.0 V
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 35
(5) S-8521F33MC
(D62F/22
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=9 V
VIN=6 V
VIN=4 V
(CDH113/22
µ
H, IRF7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=14 V
VIN=9 V
VIN=6 V
VIN=4 V
(6) S-8520B50MC
(CD54/47
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=6.0 V
VIN=9.0 V
(CD105/47
µ
H, IRF7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=14 V
VIN=9 V
VIN=6 V
(7) S-8520F50MC
(D62F/22
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=9 V
VIN=6 V
(CDH113/22
µ
H, IRF7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=14 V
VIN=9 V
VIN=6 V
(8) S-8521D50MC
(CD54/47
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=6.0 V
VIN=9.0 V
(CD105/47
µ
H, IRF7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=14 V
VIN=9 V
VIN=6 V
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
36 Seiko Instruments Inc.
(9) S-8521B50MC
(CD54/47
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=6.0 V
VIN=9.0 V
(CD105/47
µ
H, IRF7606)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=9 V
VIN=6 V
VIN=14 V
(10) S-8521F50MC
(D62F/22
µ
H, TM6201)
50
60
70
80
90
100
0.01 0.1 1 10 100 1000
IOUT [mA]
EFFI [%]
VIN=9 V
VIN=6 V
(CDH113/22
µ
H, IRF7606)
50
60
70
80
90
100
IOUT [mA]
EFFI [%]
VIN=14 V
VIN=9 V
VIN=6 V
0.01 0.1 1 10 100 1000
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 37
2. Ripple Voltage Characteristics: Ripple voltage (Vrip)-Input voltage (VIN) (L: CD105 / 47 µF, Tr:
2SA1213, SBD: MA720)
(1) S-8520D30MC (2) S-8521D30MC
(COUT=47 µF×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=500 mA
IOUT=100 mA
IOUT=0.1 mA
(COUT=47
µ
F×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=0.1 mA
IOUT=500 mA
IOUT=100 mA
(3) S-8520B30MC (4) S-8521B30MC
(COUT=22
µ
F×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=0.1 mA
IOUT=100 mA
IOUT=500 mA
(COUT=22 µF×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=0.1 mA
IOUT=500 mA
IOUT=100 mA
(5) S-8520F33MC (6) S-8521F33MC
(COUT=22 µF)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=500 mA
IOUT=100 mA
IOUT=0.1 mA
(COUT=22 µF)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=500 mA
IOUT=100 mA
IOUT=0.1 mA
(7) S-8520D50MC (8) S-8521D50MC
(COUT=47
µ
F×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=0.1 mA
IOUT=100 mA
IOUT=500 mA
(COUT=47 µF×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT =500 mA
IOUT =100 mA
IOUT =0.1 mA
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
S-8520 / 8521 Series Rev.7.5_00
38 Seiko Instruments Inc.
(9) S-8520B50MC (10) S-8521B50MC
(COUT=22
µ
F×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT =500 mA
IOUT =100 mA
IOUT =0.1 mA
(COUT=22
µ
F×2)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=0.1 mA
IOUT=500 mA
IOUT=100 mA
(11) S-8520F50MC (12) S-8521F50MC
(COUT=22 µF)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=500 mA
IOUT=100 mA
IOUT=0.1 mA
(COUT=22
µ
F)
0
40
80
120
160
200
240
2 4 6 8 10 12 14 16
VIN [V]
Vrip [mV]
IOUT=0.1 mA
IOUT=100 mA
IOUT=500 mA
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5_00 S-8520 / 8521 Series
Seiko Instruments Inc. 39
3. PWM / PFM switching characteristics: Input voltage (VIN)-Output current (IOUT)
(1) S-8521D30MC (2) S-8521B30MC
2
6
10
14
1 10 100 1000
IOUT [mA]
VIN [V]
2
6
10
14
1 10 100 1000
IOUT [mA]
VIN [V]
(3) S-8521F33MC (4) S-8521D510MC
2
6
10
14
1 10 100 1000
IOUT [mA]
VIN [V]
2
6
10
14
1 10 100 1000
IOUT [mA]
VIN [V]
(5) S-8521B50MC (6) S-8521F50MC
2
6
10
14
1 10 100 1000
IOUT [mA]
VIN [V]
2
6
10
14
1 10 100 1000
IOUT [mA]
VIN [V]
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
2.9±0.2
1.9±0.2
0.95±0.1
0.4±0.1
0.16 +0.1
-0.06
123
4
5
No. MP005-A-P-SD-1.2
MP005-A-P-SD-1.2
SOT235-A-PKG Dimensions
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
ø1.5 +0.1
-0 2.0±0.05
ø1.0 +0.2
-0 4.0±0.1
1.4±0.2
0.25±0.1
3.2±0.2
123
45
No. MP005-A-C-SD-2.1
MP005-A-C-SD-2.1
SOT235-A-Carrier Tape
Feed direction
4.0±0.1(10 pitches:40.0±0.2)
No.
TITLE
SCALE
UNIT mm
Seiko Instruments Inc.
12.5max.
9.0±0.3
ø13±0.2
(60°) (60°)
QTY. 3,000
No. MP005-A-R-SD-1.1
MP005-A-R-SD-1.1
SOT235-A-Reel
Enlarged drawing in the central part
•
The information described herein is subject to change without notice.
• Seiko Instruments Inc. is not responsible for any problems caused by circuits or diagrams described herein
whose related industrial properties, patents, or other rights belong to third parties. The application circuit
examples explain typical applications of the products, and do not guarantee the success of any specific
mass-production design.
• When the products described herein are regulated products subject to the Wassenaar Arrangement or other
agreements, they may not be exported without authorization from the appropriate governmental authority.
• Use of the information described herein for other purposes and/or reproduction or copying without the
express permission of Seiko Instruments Inc. is strictly prohibited.
• The products described herein cannot be used as part of any device or equipment affecting the human
body, such as exercise equipment, medical equipment, security systems, gas equipment, or any apparatus
installed in airplanes and other vehicles, without prior written permission of Seiko Instruments Inc.
• Although Seiko Instruments Inc. exerts the greatest possible effort to ensure high quality and reliability, the
failure or malfunction of semiconductor products may occur. The user of these products should therefore
give thorough consideration to safety design, including redundancy, fire-prevention measures, and
malfunction prevention, to prevent any accidents, fires, or community damage that may ensue.
