S-8520A28MC-AVN-T2 - Seiko Instruments, Inc.

Rev.7.4_10

Seiko Instruments Inc. 1

S-8520/8521 Series

PWM Control & PWM/PFM Control

Step-Down Switching Regulator-Controllers

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.

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Features: 



Applications:

•Low current consumption:

In operation: 60 µA max. (A & B Series)

21 µA max. (C & D Series)

100 µA max. (E & F Series)

When powered off: 0.5 µA max.

•Input voltage:

2.5 V to 16 V (B, D, F Series)

2.5 V to 10 V (A, C, E Series)

•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)

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).

•On-board power supplies of battery devices for

portable telephones, electronic notebooks, PDAs,

and the like.

•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.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

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Block Diagram:

VSS

VOUT

SD COUT

VON / OFF

ON / OFF

Reference Voltage

Source with Soft Start

PWM or

PWM/PFM-

Switched Control

Circuit

Note: The diode inside the IC is a parasitic diode.

Oscillation

Circuit

VIN

EXT

VIN CIN

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: 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-switched control

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 3

2. Product List (As of September 1, 2000)

A & B Series (Oscillation Frequency of 180 kHz)

Item

Output Voltage

(V)

S-8520AXXMC

Series

S-8521AXXMC

Series

S-8520BXXMC

Series

S-8521BXXMC

Series

1.6 

1.8 

S-8520B18MC-ARD-T2 S-8521B18MC-ATD-T2

1.9 

S-8521B19MC-ATE-T2

2.0 

S-8521B20MC-ATF-T2

2.1 S-8520A21MC-AVG-T2 

S-8521B21MC-ATG-T2

2.5 S-8520A25MC-AVK-T2 S-8521A25MC-AXK-T2 S-8520B25MC-ARK-T2 S-8521B25MC-ATK-T2

2.7 S-8520A27MC-AVM-T2 S-8521A27MC-AXM-T2 S-8520B27MC-ARM-T2 S-8521B27MC-ATM-T2

2.8 S-8520A28MC-AVN-T2 S-8521A28MC-AXN-T2 S-8520B28MC-ARN-T2 S-8521B28MC-ATN-T2

2.9 S-8520A29MC-AVO-T2 S-8521A29MC-AXO-T2 S-8520B29MC-ARO-T2 S-8521B29MC-ATO-T2

3.0 S-8520A30MC-AVP-T2 S-8521A30MC-AXP-T2 S-8520B30MC-ARP-T2 S-8521B30MC-ATP-T2

3.1 S-8520A31MC-AVQ-T2 S-8521A31MC-AXQ-T2 S-8520B31MC-ARQ-T2 S-8521B31MC-ATQ-T2

3.2 S-8520A32MC-AVR-T2 S-8521A32MC-AXR-T2 S-8520B32MC-ARR-T2 S-8521B32MC-ATR-T2

3.3 S-8520A33MC-AVS-T2 S-8521A33MC-AXS-T2 S-8520B33MC-ARS-T2 S-8521B33MC-ATS-T2

3.4 S-8520A34MC-AVT-T2 S-8521A34MC-AXT-T2 S-8520B34MC-ART-T2 S-8521B34MC-ATT-T2

3.5 S-8520A35MC-AVU-T2 S-8521A35MC-AXU-T2 S-8520B35MC-ARU-T2 S-8521B35MC-ATU-T2

3.6 S-8520A36MC-AVV-T2 S-8521A36MC-AXV-T2 S-8520B36MC-ARV-T2 S-8521B36MC-ATV-T2

5.0 S-8520A50MC-AWJ-T2 S-8521A50MC-AYJ-T2 S-8520B50MC-ASJ-T2 S-8521B50MC-AUJ-T2

C & D Series (Oscillation Frequency of 60 kHz)

Item

Output Voltage

(V)

S-8520CXXMC

Series

S-8521CXXMC

Series

S-8520DXXMC

Series

S-8521DXXMC

Series

1.6 S-8521C16MC-BTB-T2 S-8521D16MC-BXB-T2

2.0 

S-8521D20MC-BXF-T2

2.5 S-8520C25MC-BRK-T2 S-8521C25MC-BTK-T2 S-8520D25MC-BVK-T2 S-8521D25MC-BXK-T2

2.7 S-8520C27MC-BRM-T2 S-8521C27MC-BTM-T2 S-8520D27MC-BVM-T2 S-8521D27MC-BXM-T2

2.8 S-8520C28MC-BRN-T2 S-8521C28MC-BTN-T2 S-8520D28MC-BVN-T2 S-8521D28MC-BXN-T2

2.9 S-8520C29MC-BRO-T2 S-8521C29MC-BTO-T2 S-8520D29MC-BVO-T2 S-8521D29MC-BXO-T2

3.0 S-8520C30MC-BRP-T2 S-8521C30MC-BTP-T2 S-8520D30MC-BVP-T2 S-8521D30MC-BXP-T2

3.1 S-8520C31MC-BRQ-T2 S-8521C31MC-BTQ-T2 S-8520D31MC-BVQ-T2 S-8521D31MC-BXQ-T2

3.2 S-8520C32MC-BRR-T2 S-8521C32MC-BTR-T2 S-8520D32MC-BVR-T2 S-8521D32MC-BXR-T2

3.3 S-8520C33MC-BRS-T2 S-8521C33MC-BTS-T2 S-8520D33MC-BVS-T2 S-8521D33MC-BXS-T2

3.4 S-8520C34MC-BRT-T2 S-8521C34MC-BTT-T2 S-8520D34MC-BVT-T2 S-8521D34MC-BXT-T2

3.5 S-8520C35MC-BRU-T2 S-8521C35MC-BTU-T2 S-8520D35MC-BVU-T2 S-8521D35MC-BXU-T2

3.6 S-8520C36MC-BRV-T2 S-8521C36MC-BTV-T2 S-8520D36MC-BVV-T2 S-8521D36MC-BXV-T2

5.0 S-8520C50MC-BSJ-T2 S-8521C50MC-BUJ-T2 S-8520D50MC-BWJ-T2 S-8521D50MC-BYJ-T2

E & F Series (Oscillation Frequency of 300 kHz)

Item

Output Voltage

(V)

S-8520EXXMC

Series

S-8521EXXMC

Series

S-8520FXXMC

Series

S-8521FXXMC

Series

1.5 S-8521E15MC-BLA-T2 

1.8 S-8520E18MC-BJD-T2 S-8521E18MC-BLD-T2 S-8520F18MC-BND-T2 S-8521F18MC-BPD-T2

2.0 S-8521E20MC-BLF-T2 

2.5 S-8520E25MC-BJK-T2 S-8520F25MC-BNK-T2 

2.7 

S-8520F27MC-BNM-T2 

3.0 S-8520E30MC-BJP-T2 S-8521E30MC-BLP-T2 S-8520F30MC-BNP-T2 S-8521F30MC-BPP-T2

3.3 S-8520E33MC-BJS-T2 S-8521E33MC-BLS-T2 S-8520F33MC-BNS-T2 S-8521F33MC-BPS-T2

3.4 

S-8520F34MC-BNT-T2 

3.5 S-8521E35MC-BLU-T2 

5.0 S-8520E50MC-BKJ-T2 S-8521E50MC-BMJ-T2 S-8520F50MC-BOJ-T2 S-8521F50MC-BQJ-T2

For the availability of product samples listed above, contact the SII Sales Department.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

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

Pin Assignment:

SOT-23-5

Top view

1 2 3

5 4

Figure 2

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Absolute Maximum Ratings:

(Ta = 25 οC unless otherwise specified)

Item Symbol Ratings Unit

VIN pin voltage VIN *1 VSS −0.3 to VSS+12 or VSS+18 V

VOUT pin voltage VOUT VSS −0.3 to VSS+12 or VSS+18 V

ON/OFF pin voltage VON/OFF

*1 VSS −0.3 to VSS+12 or VSS+18 V

EXT pin voltage VEXT VSS −0.3 to VIN+0.3 V

EXT pin current IEXT ±50 mA

Power dissipation PD250 mW

Operating temperature range TOPR −40 to +85 οC

Storage temperature range TSTG −40 to +125 οC

*1. VSS+12 V for S-8520/21A/C/E; VSS+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.

Pin No. Pin Name Function

1ON/OFF

Power-off 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

5 VIN IC power supply pin

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 5

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Electrical Characteristics:

1. S-8520/21 A & B Series

(Ta =25 °C, unless otherwise specified)

Parameter Symbol Conditions Min. Typ. Max. Units Measurement

Circuit

Output voltage *1 VOUT(E) − VOUT(S)

× 0.976

VOUT(S) VOUT(S)

×1.024

V 3

Input voltage VIN S-8520/21A Series 2.5 − 10.0 V 2

S-8520/21B Series 2.5 − 16.0

Current consumption 1 ISS1 VOUT = VOUT(S) × 1.2 − 35 60 µA 2

Current consumption during

power off

ISSS VON/OFF = 0 V − − 0.5 µA 2

S-8520/21X15 − 24 −2.3 −4.5 −

S-8520/21X25 − 34 −3.7 −7.0 −

IEXTH VEXT =VIN−0.4 V S-8520/21X35 − 44 −5.3 −9.3 −

S-8520/21X45 − 54 −6.7 −11.3 −

EXT pin output current S-8520/21X55 − 60 −8.0 −13.3 − mA −

S-8520/21X15 − 24 +4.3 +8.4 −

S-8520/21X25 − 34 +7.0 +13.2 −

IEXTL VEXT = 0.4 V S-8520/21X35 − 44 +9.9 +17.5 −

S-8520/21X45 − 54 +12.6 +21.4 −

S-8520/21X55 − 60 +15.0 +25.1 −

Line regulation ∆VOUT1 VIN = VOUT(S) ×1.2 to ×1.4 *4 − 30 60 mV 3

Load regulation ∆VOUT2 Load current =10µA to IOUT(See below)

×1.25

− 30 60 mV 3

Output voltage temperature

coefficient

∆VOUT

/∆Ta

Ta= − 40 °C to 85 °C − ±VOUT(S)

× 5E-5

− V/°C 3

Oscillation frequency fosc Measure waveform

at EXT pin

VOUT(S) ≥ 2.5 V 153 180 207 kHz 3

VOUT(S) ≤ 2.4 V 144 180 216

PWM/PFM-control switch

duty ratio *2 PFM Duty Measure waveform at EXT pin under no

load.

15 25 40 % 3

Power-Off pin VSH Evaluate oscillation at EXT pin 1.8 − − V 2

input voltage VSL Evaluate oscillation stop at EXT pin − − 0.3

Power-Off pin ISH − −0.1 − 0.1 µA 1

input leakage current ISL − −0.1 − 0.1 µA 1

Soft-Start time TSS − 4.0 8.0 16.0 ms 3

Overload detection time *3 TPRO Duration from the time VOUT is reduced

to 0 V to the time the EXT pin obtains

VIN.

2.0 4.0 8.0 ms 2

Efficiency EFFI − − 93 − % 3

Conditions:

The recommended components are connected to the IC, unless otherwise indicated. VIN = VOUT(S) × 1.2 [V],

IOUT = 120 [mA] (VIN= 2.5 V, if VOUT(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 (Rb) : 0.68 kΩ

Base capacitor (Cb) : 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. VOUT(S) Specified output voltage value.

VOUT(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. VIN = 2.5 V to 2.94 V, if VOUT(S) ≤2.0 V.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

2. S-8520/21 C & D Series

(Ta = 25 °C unless otherwise specified)

Parameter Symbol Conditions Min. Typ. Max. Units Measuremen

t Circuit

Output voltage *1 VOUT(E) −VOUT(S)

× 0.976

VOUT(S) VOUT(S)

× 1.024

Input voltage VIN S-8520/21C Series 2.5 −10.0 V 2

S-8520/21D Series 2.5 −16.0

Current consumption 1 ISS1 VOUT = VOUT(S) × 1.2 −10 21 µA2

Current consumption during

power-off

ISSS VON/OFF = 0 V −−

0.5 µA2

S-8520/21X15 − 24 −2.3 −4.5 −

S-8520/21X25 − 34 −3.7 −7.0 −

IEXTH VEXT = VIN−0.4 V S-8520/21X35 − 44 −5.3 −9.3 −

S-8520/21X45 − 54 −6.7 −11.3 −

EXT pin output current S-8520/21X55 − 60 −8.0 −13.3 −mA −

S-8520/21X15 − 24 +4.3 +8.4 −

S-8520/21X25 − 34 +7.0 +13.2 −

IEXTL VEXT = 0.4 V S-8520/21X35 − 44 +9.9 +17.5 −

S-8520/21X45 − 54 +12.6 +21.4 −

S-8520/21X55 − 60 +15.0 +25.1 −

Line regulation ∆VOUT1 VIN = VOUT(S) ×1.2 to ×1.4 *4 −30 60 mV 3

Load regulation ∆VOUT2 Load current =10 µA to IOUT(See below)

×1.25

−30 60 mV 3

Output voltage temperature

coefficient

∆VOUT

/∆Ta Ta = − 40 °C to 85 °C−± VOUT(S)

× 5E-5

−V/°C3

Oscillation frequency fosc Measure waveform

at EXT pin

VOUT(S) ≥ 2.5 V 48 60 72 kHz 3

VOUT(S) ≤ 2.4 V 45 60 75

PWM/PFM-control switch

duty ratio *2 PFM

Duty

Measure waveform at EXT pin under no

load.

15 25 40 %3

Power-Off pin VSH Evaluate oscillation at EXT pin 1.8 −− V2

input voltage VSL Evaluate oscillation stop at EXT pin −−

0.3

Power-Off pin ISH −−0.1 −0.1 µA1

input leakage current ISL −−0.1 −0.1 µA1

Soft-Start time TSS −6.0 12.0 24.0 ms 3

Overload detection time *3 TPRO Duration from the time VOUT is reduced

to 0 V to the time the EXT pin obtains

VIN.

7.0 14.0 28.0 ms 2

Efficiency EFFI −−

93 −% 3

Conditions:

The recommended components are connected to the IC, unless otherwise indicated. VIN = V

OUT × 1.2 [V],

IOUT = 120 [mA] (VIN= 2.5 V, if VOUT(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 (Rb) : 0.68 kΩ

Base capacitor (Cb) : 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. VOUT(S) Specified output voltage value.

VOUT(E) Actual output voltage value.

*2. Applicable to the S-8521C Series and S-8521D Series.

*3. Applicable to the S-8520C Series and S-8521C Series.

*4. VIN = 2.5 V to 2.94 V, if VOUT(S) ≤2.0 V.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 7

3. S-8520/21 E & F Series

(Ta = 25 °C unless otherwise specified)

Parameter Symbol Conditions Min. Typ. Max. Units Measurement

Circuit

Output voltage *1 VOUT(E) −VOUT(S)

×0.976

VOUT(S) VOUT(S)

× 1.024

Input voltage VIN S-8520/21E Series 2.5 −10.0 V 2

S-8520/21F Series 2.5 −16.0

Current consumption 1 ISS1 VOUT = VOUT(S) × 1.2 −60 100 µA2

Current consumption during

power-off

ISSS VON/OFF = 0 V −−

0.5 µA2

S-8520/21X15 − 24 −2.3 −4.5 −

S-8520/21X25 − 34 −3.7 −7.0 −

IEXTH VEXT = VIN−0.4 V S-8520/21X35 − 44 −5.3 −9.3 −

S-8520/21X45 − 54 −6.7 −11.3 −

EXT pin output current S-8520/21X55 − 60 −8.0 −13.3 −mA −

S-8520/21X15 − 24 +4.3 +8.4 −

S-8520/21X25 − 34 +7.0 +13.2 −

IEXTL VEXT = 0.4 V S-8520/21X35 − 44 +9.9 +17.5 −

S-8520/21X45 − 54 +12.6 +21.4 −

S-8520/21X55 − 60 +15.0 +25.1 −

Line regulation ∆VOUT1 VIN = VOUT(S) ×1.2 to ×1.4 *4 −30 60 mV 3

Load regulation ∆VOUT2 Load current =10 µA to IOUT(See below)

×1.25

−30 60 mV 3

Output voltage temperature

coefficient

∆VOUT

/∆Ta Ta = −40 °C to 85 °C−± VOUT

× 5E-5

−V/°C3

Oscillation frequency fosc Measure waveform

at EXT pin

VOUT ≥ 2.5 V 240 300 360 kHz 3

VOUT ≤ 2.4 V 225 300 375

PWM/PFM-control switch

duty ratio *2 PFM Duty Measure waveform at EXT pin under no

load.

15 25 40 %3

Power-Off pin VSH Evaluate oscillation at EXT pin 1.8 −−V2

input voltage VSL Evaluate oscillation stop at EXT pin −−

0.3

Power-Off pin ISH −−0.1 −0.1 µA1

input leakage current ISL −−0.1 −0.1 µA1

Soft-Start time TSS −2.0 4.5 9.2 ms 3

Overload detection time *3 TPRO Duration from the time VOUT is reduced

to 0 V to the time the EXT pin obtains

VIN.

1.3 2.6 4.5 ms 2

Efficiency EFFI −−

90 −% 3

Conditions:

The recommended components are connected to the IC, unless otherwise indicated. VIN = VOUT × 1.2 [V],

IOUT = 120 [mA] (VIN= 2.5 V, if VOUT(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 (Rb) : 0.68 kΩ

Base capacitor (Cb) : 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. VOUT(S) Specified output voltage value.

VOUT(E) Actual output voltage value.

*2. Applicable to the S-8521E Series and S-8521F Series.

*3. Applicable to the S-8520E Series and S-8521E Series.

*4. VIN = 2.5 V to 2.94 V, if VOUT(S) ≤2.0 V.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.





Measurement Circuits:

EXT

VSS

ON/OFF

VOUT

open

VIN

open

VSS

ON/OFF

VIN

VOUTEXT

Oscillation

VSS

ON/OFF

0.68 kΩ

VOUT

VIN

−− V

2200 pF

EXT

Figure 3





Operation:

1. Step-Down DC-DC Converter

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 converters of the S-8520 Series, the pulse width varies in a range from 0 % to 100 %, according to the

load current, and yet ripple voltage produced by the switching can easily be removed through a filter

because the switching frequency remains constant. Therefore, these converters provide a low-ripple

power over broad ranges of input voltage and load current.

1.2 PWM/PFM-Switched Control (S-8521 Series)

The S-8521 Series consists of DC/DC converters capable of automatically switching the pulse-wide

modulation system (PWM) over to the pulse-frequency modulation system (PFM), and vice versa,

according to the load current. This series of converters features low current consumption.

In a region of high output load currents, the S-8521 Series converters function with PWM control, where

the pulse-width duty varies from 25 % to 100 %. This function helps keep the ripple power low.

For certain low output load currents, the converters are switched over to PFM control, whereby pulses

having their pulse-width duty fixed at 25 % are skipped depending on the quantity of the load current, and

are output to a switching transistor. This causes the oscillation circuit to produce intermittent oscillation.

As a result, current consumption is reduced and efficiency losses are prevented under low loads.

Especially for output load currents in the region of 100 µA, these DC/DC converters can operate at

extremely high efficiency.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 9

2. Power-Off Pin (ON/OFF Pin)

This pin deactivates or activates the step-down operation.When the power-off 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 power-off pin is configured as shown in Figure 4. 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 V to 1.8 V to the pin, lest the current consumption increase. When this power-off pin is not used,

leave it coupled to the VIN pin.

3. Soft-Start Function

The S-8520/21 Series comes with a built-in soft-start circuit. This circuit enables the output voltage to

rise gradually over the specified soft-start time, when the power is switched on or when the power-off 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 (see Figure 5). 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

0 V

3 V Power switched on

Figure 5 Waveforms of Output Voltage and Rush Current at Soft-Start

4. Overload Protection Circuit (A, C, E Series)

The S-8520/21A, S-8520/21C Series, and S-8520/21E 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

VSS

Figure 4

Power-Off Pin CR Oscillation

Circuit

Output

Voltage

“H” Activated Set value

“L” Deactivated VSS

ON/OFF

VIN

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

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 6 Waveforms Appearing at EXT Pin As the Overload Protection Circuit Operates

5. 100 %

% Duty Cycle

The S-8520/21 Series operates with a maximum duty cycle of 100 %. When a B, D, F Series product 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, E Series product 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.





Selection of Series Products and Associated External Components

1. Method for selecting series products

The S-8520/21 Series is classified into 12 types, according to the way the control systems (PWM and

PWM/PFM-Switched), 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.





Control systems:

Two different control systems are available: PWM control system (S-8520 Series) and PWM/PFM-

switched 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-

switched 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.





Oscillation frequencies:

Three oscillation frequencies--180 kHz (A & B Series) and 60 kHz (C & D Series), 300 kHz (E, F

Series)--are available.

Because of their high oscillation frequency and low-ripple voltage the A, B, E, F Series 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

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 11

make the A & B Series ideal products for downsizing the associated equipment.

On the other hand, the C & D Series, having a lower oscillation frequency, are characterized by a

small self-consumption of current and excellent efficiency under light loads. In particular, the D

Series, which employs a PWM/PFM-switched control system, enables the operation efficiency to be

improved drastically when the output load current is approximately 100 µA. (See Reference Data.)





Overload protection circuit:

Products can be chosen either with an overload protection circuit (A, C, E Series) or without one (B,

D, F Series).

Products with an overload protection circuit (A, C, E Series) 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 Series 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 Series) or 16 V (B, D, F Series), depending on whether the product comes with

an overload protection circuit built in.

The table below 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 (O).

S-8520 S-8521

ABCDEF 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

     

The symbol "" denotes an indispensable condition, while the symbol "" indicates that the corresponding

series has superiority in that aspect. The symbol "" indicates particularly high superiority.

2. Inductor

The inductance value greatly affects the maximum output current IOUT and the efficiency η.

As the L-value is reduced gradually, the peak current Ipk increases, to finally reach the maximum output

current IOUT when the L-value has fallen to a certain point. If the L-value is made even smaller, IOUT will

begin decreasing because the current drive capacity of the switching transistor becomes insufficient.

Conversely, as the L-value is augmented, the loss due to Ipk in the switching transistor will decrease until

the efficiency is maximized at a certain L-value. If the L-value is made even larger, the loss due to the

series resistance of the coil will increase to the detriment of the efficiency.

If the L-value is increased in an S-8520/21 Series product, the output voltage may turn unstable in some

cases, depending on the conditions of the input voltage, output voltage, and the load current. Perform

thorough evaluations under the conditions of actual service and decide on an optimum L-value.

In many applications, selecting a value of A/B/C/D Series 47µH, E, F Series 22 µH will allow a S-8520/21

Series product to yield its best characteristics in a well balanced manner.

When choosing an inductor, pay attention to its allowable current, since a current applied in excess of

the allowable value will cause the inductor to produce magnetic saturation, leading to a marked decline in

efficiency.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

Therefore, select an inductor in which the peak current Ipk will not surpass its allowable current at any

moment. The peak current Ipk is represented by the following equation in continuous operation mode:

(VOUT + VF)× (VIN − VOUT)

IPK = IOUT +2× fosc × L × (VIN + VF)

Where fosc is the oscillation frequency, L the inductance value of the coil, 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 47µF 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 47µF to 100 µF can serve as a rough yardstick for this selection.

5. External Switching Transistor

The S-8520/21 Series can be operated with an external switching transistor of the enhancement (Pch)

MOS FET type or bipolar (PNP) typ.

5.1 Enhancement MOS FET type

The EXT pin of the S-8520/21 Series is capable of directly driving a Pch power MOS FET with a gate

capacity of some 1000 pF.

When a Pch power 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 Pch power 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

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 13

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 the peak current 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 Automatic Loom

Works, Ltd. IRF7606, a standard of International Rectifier, was used for applications with an input

voltage range over 10 V. Refer to "Reference Data."

5.2 Bipolar PNP type

Figure 7 shows a sample circuit diagram using Toshiba 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

2SA1213-Y

VIN

RbCb

Figure 7

The Rb-value is given by the following equation:

Ib|IEXTL|

0.4

VIN−0.7

Rb=−

Find the necessary base current Ib using the hFE - value of bipolar transistor by the equation, Ib = Ipk/hFE,

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 7, the

switching loss will be reduced, leading to a higher efficiency.

Select a Cb-value by using the following equation as a guide:

2π xRb x f OSC

x 0.7

Cb≤

However, the practically-reasonable Cb value differs depending upon the characteristics of the bipolar

transistor. Optimize the Cb value based on the experiment result.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.





 Standard Circuits:

(1) Using a bipolar transistor:

VSS

VOUT

VIN CIN

SD COUT

VON / OFF

ON / OFF

Reference Voltage

Source with Soft-Start

−

PWM or

PWM/PFM-

Switched Control

Circuit

Oscillation

Circuit

VIN

EXT

Figure 8

(2) Using a Pch MOS-FET transistor

VSS

VOUT

SD COUT

VON / OFF

ON / OFF

Reference Voltage

Source with Soft-Start

−

PWM or

PWM/PFM-

Switched Control

Circuit

Oscillation

Circuit

VIN

EXT

VIN CIN

Figure 9





Precautions:

Install the external capacitors, diode, coil, and other peripheral components as close to the IC as possible,

and secure grounding at a single location.

Any switching regulator intrinsically produces a ripple voltage and spike noise, which are largely dictated by

the coil and capacitors in use. When designing a circuit, first test them on actual equipment.

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 overcurrents 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 will not surpass the allowable dissipation of the

package. (especially at the time of high temperature)

200

100

050 100 150

Power

dissipation

(mW)

Temperature Ta (0C)

Figure 10 Power dissipation of an SOT-23-5 Package (Free-Air)

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 15

 Do not apply an electrostatic discharge to this IC that exceeds the performance ratings of

the built-in electrostatic protection circuit.

 Seiko Instruments Inc. shall not be responsible for any patent infringement by products including the S-

8520/8521 Series in connection with the method of using the S-8520/8521 Series in such products, the

product specifications or the country of destination thereof.





Application Circuits:

1. External adjustment of output voltage

The S-8520/21 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, RB,

and capacitor CC are added, as illustrated in Figure 11. Moreover, a temperature gradient can be

obtained by inserting a thermistor or other element in series with RA and RB.

S-8520/21 Series

ON/OFF

CCRA

VOUT

VSS

−

VIN

OUT

EXT

−

Reference Voltage

Source with

Soft-Start

PWM or

PWM/PFM-

Switched Control

Circuit

Oscillation

Cirucuit

Figure 11

The S-8520 and 21 Series have an internal impedance of R1 and R2 between the VOUT and the VSS

pin, as shown in Figure 11.

Therefore, the output voltage (OUT) is determined by the output voltage value VOUT of the S-8520/21

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 // ( R1 + R2 )) (Note: // denotes a combined resistance in parallel.)

The voltage accuracy of the output 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 external resistances 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 internal resistances 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 output voltage OUT are expressed by the following equations:

OUTmin = VOUT × 0.976 + VOUT × 0.976 × RAmin ÷ ( RBmax // ( R1 + R2 )max )

OUTmax = VOUT × 1.024 + VOUT × 1.024 × RAmax ÷ ( RBmin // ( R1 + R2 )min )

The voltage accuracy of the output OUT cannot be made higher than the output voltage accuracy (VOUT ±

2.4 %) of the IC itself, without adjusting the external resistances 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 externally

connected resistances RA and RB and the absolute value of internal resistances R1 and R2 in the IC.

In particular, to suppress the influence of deviations in internal resistances R1 and R2 in the IC, a major

contributor to deviations in the output OUT, the external resistances RA and RB must be limited to a much

smaller value than that of internal resistances R1 and R2 in the IC.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

On the other hand, a reactive current flows through external resistances 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 external resistance RA

and RB be made sufficiently large.

However, too large a value (more than 1 MΩ) for the external resistances 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 output 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 internal resistances R1 and R2 in the IC vary with the output voltage of

the S-8520/21 Series, and are broadly classified as follows:

 Output voltage 1.5 V to 2.0 V → 5.16 MΩ to 28.9 MΩ

 Output voltage 2.1 V to 2.5 V → 4.44 MΩ to 27.0 MΩ

 Output voltage 2.6 V to 3.3 V → 3.60 MΩ to 23.3 MΩ

 Output voltage 3.4 V to 4.9 V → 2.44 MΩ to 19.5 MΩ

 Output voltage 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 output OUT.

R1 + R2 = 2 ÷ (1 ÷ maximum deviation in absolute value of internal resistances R1 and R2 in IC + 1 ÷

minimum deviation in absolute value of internal resistances R1 and R2 of IC)

Moreover, add a capacitor CC in parallel to the external resistance RA in order to avoid output oscillations

and other types of instability (See Figure 11).

Make sure that CC is larger than the value given by the following equation:

CC (F) ≥ 1 ÷ (2 x π x RA (Ω) x 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 output 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.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 17



 

 Characteristics of Major Parameters (Typical values):

(1) (2)

ISS1-VIN

S-8520/21(Fosc:60 kHz)

2 4 6 8 10 12 14 16

VIN(V)

ISS1

(µA)

Ta=−40

Ta=85

Ta=25

ISS1-VIN

S-8520/21(Fosc:180 kHz)

2 4 6 8 10 12 14 16

VIN(V)

ISS1

(µA) Ta=−40

Ta=85

Ta=25

(3) (4)

ISS1-VIN

S-8520/21(Fosc:300 kHz)

2 4 6 8 10 12 14 16

VIN(V)

ISS1

(µA)

Ta=−40

Ta=85

Ta=25

Fosc-VIN

S-8520/21(Fosc:60 kHz)

2 4 6 8 10 12 14 16

VIN(V)

Fosc

(kHz)

Ta=−40

Ta=85

Ta=25

(5) (6)

Fosc-VIN

S-8520/21(Fosc:180 kHz)

140

150

160

170

180

190

200

210

220

2 4 6 8 10 12 14 16

VIN(V)

Fosc

(kHz)

Ta=−40

Ta=85

Ta=25

Fosc-VIN

S-8520/21(Fosc:300 kHz)

240

260

280

300

320

340

360

2 4 6 8 10 12 14 16

VIN(V)

Fosc

(kHz)

Ta=−40

Ta=85

Ta=25

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

(7) (8)

IEXTH-VIN

S-8520/21

−60

−50

−40

−30

−20

−10

2 4 6 8 10 12 14 16

VIN(V)

IEXTH

(mA)

Ta=−40

Ta=85

Ta=25

IEXTL-VIN

S-8520/21

2 4 6 8 10 12 14 16

VIN(V)

IEXTL

(mA)

Ta=−40

Ta=85

Ta=25

(9) (10)

TSS-VIN

S-8520/21(Fosc:60 kHz)

2 4 6 8 10 12 14 16

VIN(V)

TSS

(ms)

Ta=−40

Ta=85

Ta=25

TSS-VIN

S-8520/21(Fosc:180 kHz)

2 4 6 8 10 12 14 16

VIN(V)

TSS

(ms)

Ta=−40

Ta=85

Ta=25

(11) (12)

TSS-VIN

S-8520/21(Fosc:300 kHz)

2 4 6 8 10 12 14 16

VIN(V)

TSS

(ms)

Ta=−40

Ta=85

Ta=25

TPRO-VIN

S-8520/21(Fosc:60 kHz)

2 4 6 8 10 12 14 16

VIN(V)

TPRO

(ms)

Ta=−40

Ta=85

Ta=25

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 19

(13) (14)

TPRO-VIN

S-8520/21(Fosc:180 kHz)

2 4 6 8 10 12 14 16

VIN(V)

TPRO

(ms)

Ta=−40

Ta=85

Ta=25

TPRO-VIN

S-8520/21(Fosc:300 kHz)

2 4 6 8 10 12 14 16

VIN(V)

TPRO

(ms) Ta=−40

Ta=85

Ta=25

(15) (16)

VSH-VIN

S-8520/21

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

Ta=85

Ta=25

VSL-VIN

S-8520/21

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

Ta=85

Ta=25

(17) (18)

VOUT-VIN

S-8521B30MC

(

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=500 mA

IOUT=100 mA

IOUT=0.1 mA

VOUT-VIN

S-8521B50MC (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=0.1 mA

IOUT=500 mA

IOUT=100 mA

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

(19) (20)

VOUT-VIN

S-8521F33MC (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 10121416

VIN(V)

VOUT

(V)

IOUT=500 mA

IOUT=100 mA

IOUT=0.1 mA

VOUT-VIN

S-8521F50MC (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

246810121416

VIN(V)

VOUT

(V)

IOUT=500 mA

IOUT=100 mA

IOUT=0.1 mA

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 21





Transient Response Characteristics:

1. Power-On (VIN: 0 V→

→→

→3.6 V or 4.0 V, 0 V→

→→

→9.0 V IOUT: No-load)

S-8520/1C30MC (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

S-8520/1C30MC (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

S-8520/1A30MC (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

S-8520/1A30MC (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

S-8520/1E33MC (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

S-8520/1E33MC (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

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

2. Power-Off Terminal Response (VON/OFF: 0 V→

→→

→1.8 V IOUT : No-load)

S-8520/1C30MC (VIN:3.6 V)

t(2 ms/div)

VON/OFF

VOUT

(1 V/div)

0 V

3 V

0 V

3 V

S-8520/1C30MC (VIN:9.0 V)

t(2 ms/div)

VON/OFF

VOUT

(1 V/div)

0 V

3 V

0 V

3 V

S-8520/1A30MC (VIN:3.6 V)

t(1 ms/div)

VON/OFF

VOUT

(1 V/div)

0 V

3 V

0 V

3 V

S-8520/1A30MC (VIN:9.0 V)

t(1 ms/div)

VON/OFF

VOUT

(1 V/div)

0 V

3 V

0 V

3 V

S-8520/1E33MC (VIN:4.0 V)

t(1 ms/div)

VON/OFF

VOUT

(1 V/div)

0 V

3 V

0 V

3 V

S-8520/1E33MC (VIN:9.0 V)

t(1 ms/div)

VON/OFF

VOUT

(1 V/div)

0 V

3 V

0 V

3 V

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 23

3. Supply Voltage Variation (VIN: 4 V→

→→

→9 V, 9 V→

→→

→4 V)

S-8520/1C33MC (IOUT:10 mA)

t(0.5 ms/div)

VIN

(2.5 V/div)

VOUT

(0.2 V/div)

0 V

10 V

S-8520/1C33MC (IOUT:500 mA)

t(0.5 ms/div)

VIN

(2.5 V/div)

VOUT

(0.2 V/div)

0 V

10 V

S-8520/1A30MC

(IOUT:10 mA)

t(0.5 ms/div)

VIN

(2.5 V/div)

VOUT

(0.2 V/div)

0 V

10 V

S-8520/1A30MC (IOUT:500 mA)

t(0.5 ms/div)

VIN

(2.5 V/div)

VOUT

(0.2 V/div)

0 V

10 V

S-8520/1E33MC (IOUT:10 mA)

t(0.5 ms/div)

VIN

(2.5 V/div)

VOUT

(0.2 V/div)

0 V

10 V

S-8520/1E33MC (IOUT:500 mA)

t(0.5 ms/div)

VIN

(2.5 V/div)

VOUT

(0.2 V/div)

0 V

10 V

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

4. Load Variation (Vin: 3.6V or 4.0V Iout: 0.1mA→

→→

→500mA, 500mA→

→→

→0.1mA)

S-8520/1C30MC (VIN:3.6 V)

t(0.1 ms/div)

IOUT

VOUT

(0.1 V/div)

0.1 mA

500 mA

S-8520/1C30MC (VIN:3.6 V)

t(5 ms/div)

IOUT

VOUT

(0.1 V/div)

0.1 mA

500 mA

S-8520/1A30MC (VIN:3.6 V)

t(0.1 ms/div)

IOUT

VOUT

(0.1 V/div)

0.1 mA

500 mA

S-8520/1A30MC (VIN:3.6 V)

t(10 ms/div)

IOUT

VOUT

(0.1 V/div)

0.1 mA

500 mA

S-8520/1E33MC (VIN:4.0 V)

t(0.1 ms/div)

IOUT

VOUT

(0.1V/div)

0.1 mA

500 mA

S-8520/1E33MC (VIN:4.0 V)

t(5 ms/div)

IOUT

VOUT

(0.1 V/div)

0.1 mA

500 mA

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 25





External Parts 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 1 Efficiency Data

No. Product Name Output

Voltage

(V)

Inductor Transistor Diode Output

Capacitor

(µF)

Application

(1) S-8520B30MC 3.0 CD105/47 µHTM6201 MA737 47 IOUT≤1 A, VIN ≤10 V

(2) S-8520F33MC 3.3 D62F/22 µH↑MA720 22 IOUT≤0.5 A, VIN ≤10 V

(3) ↑↑CDH113/22 µHIRF7606 MA737 ↑IOUT≤1 A, VIN ≤16 V

(4) S-8521D30MC 3.0 CD54/47 µFTM6201 MA720 47×2I

OUT≤0.5 A, VIN ≤10 V

Equipment standby mode involved.

(5) ↑↑↑

IRF7606 ↑↑

IOUT≤0.5 A, VIN ≤16 V

Equipment standby mode involved.

(6) S-8521B30MC ↑CD105/47 µFTM6201 MA737 47 IOUT≤1 A, VIN ≤10 V

Equipment standby mode involved.

(7) ↑↑↑

IRF7606 ↑↑

IOUT≤1 A, VIN ≤16 V

Equipment standby mode involved.

(8) S-8521F33MC 3.3 D62F/22 µHTM6201 MA720 22 IOUT≤0.5 A, VIN≤ 10 V

Equipment standby mode involved.

(9) ↑↑CDH113/22 µHIRF7606 MA737 ↑IOUT≤1 A, VIN ≤16 V

Equipment standby mode involved.

(10) S-8520B50MC 5.0 CD54/47 µFTM6201 MA720 47 IOUT≤0.5 A, VIN≤ 10 V

(11) ↑↑CD105/47 µFIRF7606 MA737 ↑IOUT≤1 A, VIN≤16 V

(12) S-8520F50MC ↑D62F/22 µHTM6201 MA720 22 IOUT≤0.5 A, VIN ≤10 V

(13) ↑↑CDH113/22 µHIRF7606 MA737 ↑IOUT≤1 A, VIN ≤16 V

(14) S-8521D50MC ↑CD54/47 µFTM6201 MA720 47×2I

OUT≤0.5 A, VIN ≤10 V

Equipment standby mode involved.

(15) ↑↑

CD105/47 µFIRF7606 MA737 ↑IOUT≤1 A, VIN ≤16 V

Equipment standby mode involved.

(16) S-8521B50MC ↑CD54/47 µFTM6201 MA720 47 IOUT≤0.5 A, VIN ≤10 V

Equipment standby mode involved.

(17) ↑↑

CD105/47 µFIRF7606 MA737 ↑IOUT≤1 A, VIN ≤16 V

Equipment standby mode involved.

(18) S-8521F50MC ↑D62F/22 µHTM6201 MA720 22 IOUT≤0.5 A, VIN ≤10 V

Equipment standby mode involved.

(19) ↑↑CDH113/22 µHIRF7606 MA737 ↑IOUT≤1 A, VIN ≤16 V

Equipment standby mode involved.

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

Table 2 Ripple Data

No. Product Name Output

Voltage

(V)

Inductor

(µH)

Transistor Rb

(Ω)

(pF)

Diode Output

Capacitor

(µF)

(20) S-8520D30MC 3.0 CD105/47 2SA1213Y 680 2200 MA720 47×2

(21) S-8521D30MC ↑↑↑↑↑↑↑

(22) S-8520B30MC ↑↑↑↑↑↑22 ×2

(23) S-8521B30MC ↑↑↑↑↑↑↑

(24) S-8520F33MC 3.3 CDH113/22 IRF7606 −−

MA737 22

(25) S-8521F33MC ↑↑↑−−

↑↑

(26) S-8520D50MC 5.0 CD105/47 2SA1213Y 680 2200 MA720 47 ×2

(27) S-8521D50MC ↑↑↑↑↑↑↑

(28) S-8520B50MC ↑↑↑↑↑↑22 ×2

(29) S-8521B50MC ↑↑↑↑↑↑↑

(30) S-8520F50MC ↑CDH113/22 IRF7606 −−

MA737 22

(31) S-8521F50MC ↑↑↑−−↑↑

Table 3 Performance Data

Component Product

Name

Manufacturer's

Name

L-Value

(µH)

Resistance

(Ω)

Max.

Allowable

Current

(A)

Dia.

(mm)

Height

(mm)

Inductor CD54 Sumida Electric

Co., Ltd

47 0.37 0.72 5.8 4.5

CD105 ↑↑

0.17 1.28 10.0 5.4

CDH113 ↑22 0.09 1.44 11.0 3.7

D62F Toko ↑0.25 0.70 6.0 2.7

Diode MA720 Matsushita

Electronics

Corporation

Forward current 500 mA (When VF = 0.55 V)

MA737 ↑Forward current 1.5 A (When VF = 0.5 V)

Output Capacity F93 Nichicon

TE Matsushita

Electronics

Corporation

External Transistor

(Bipolar PNP)

2SA1213Y Toshiba

Corporation

VCEO 50 V max. , IC−2A max., hFE 120 to 240

SOT-89-3 PKG

External Transistor

(MOS FET)

TM6201 Toyota Automatic

Loom Works, Ltd.

VGS 12 V max. , ID −2 A max. , Vth −0.7 V min. , Ciss 320 pF typ.

Ron 0.25 Ω max.(Vgs=−4.5 V), SOT-89-3 PKG

IRF7606 International

Rectifier

VGS 20 V max. , ID −2.4 A max. , Vth −1 V min. Ciss 470 pF typ.

Ron 0.15 Ω max.(Vgs=−4.5 V), Micro 8 PKG

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 27

1. Efficiency Characteristics

(1)

S-8520B30MC

IOUT − Efficiency (CD105/47 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=3.6 V

VIN=9.0 V

(2) (3)

S-8520F33MC

IOUT − efficiency (D62F/22 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=9 V

VIN=6 V

VIN=4 V

S-8520F33MC

IOUT − Efficiency (CDH113/22 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=14 V

VIN=9 V

VIN=6 V

VIN=4 V

(4) (5)

S-8521D30MC

IOUT − Efficiency (CD54/47 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=3.6 V

VIN=9.0 V

S-8521D30MC

IOUT − Efficiency (CD54/47 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=3.6 V

VIN=9.0 V

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

(6) (7)

S-8521B30MC

IOUT − Efficiency (CD105/47 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=3.6 V

VIN=9.0 V

S-8521B30MC

IOUT − Efficiency (CD105/47 µH,IFR7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=3.6 V

VIN=9.0 V

(8) (9)

S-8521F33MC

IOUT − Efficiency (D62F/22 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=9 V

VIN=6 V

VIN=4 V

S-8521F33MC

IOUT − Efficiency (CDH113/22 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=14 V

VIN=9 V

VIN=6 V

VIN=4 V

(10) (11)

S-8520B50MC

IOUT − Efficiency (CD54/47 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=6.0 V

VIN=9.0 V

S-8520B50MC

IOUT − Efficiency (CD105/47 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=14 V

VIN=9 V

VIN=6 V

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)Efficiency

(%)

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 29

(12) (13)

S-8520F50MC

IOUT − Efficiency (D62F/22 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=9 V

VIN=6 V

S-8520F50MC

IOUT − Efficiency (CDH113/22 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=14 V

VIN=9 V

VIN=6 V

(14) (15)

S-8521D50MC

IOUT − Efficiency (CD54/47 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=6.0 V

VIN=9.0 V

S-8521D50MC

IOUT − Efficiency (CD105/47 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=14 V

VIN=9 V

VIN=6 V

(16) (17)

S-8521B50MC

IOUT − Efficiency (CD54/47 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=6.0 V

VIN=9.0 V

S-8521B50MC

IOUT − Efficiency (CD105/47 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=14 V

VIN=9 V

VIN=6 V

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

Efficiency

(%)

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

(18) (19)

S-8521F50MC

IOUT − Efficiency (D62F/22 µH,TM6201)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=9 V

VIN=6 V

S-8521F50MC

IOUT − Efficiency (CDH113/22 µH,IRF7606)

100

0.01 0.1 1 10 100 1000

IOUT (mA)

VIN=14 V

VIN=9 V

VIN=6 V

Efficiency

(%)

Efficiency

(%)

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 31

2. Ripple Voltage Characteristics(L:CD105/47µ

µµ

µF, Tr:2SA1213, SBD:MA720)

(20) (21)

Vrip−VIN

S-8520D30MC(COUT:47 µF×2)

120

160

200

240

2 4 6 8 10 12 14 16

VIN(V)

Vrip

(mV)

IOUT=100 mA

IOUT=500 mA

IOUT=0.1 mA

Vrip−VIN

S-8521D30MC(Cout:47 µF×2)

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

(22) (23)

Vrip−VIN

S-8520B30MC(COUT:22 µF×2)

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

Vrip−VIN

S-8521B30MC(COUT:22 µF×2)

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

(24) (25)

Vrip−VIN

S-8520F33MC(COUT:22 µF)

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

Vrip−VIN

S-8521F33MC(COUT:22 µF)

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

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

S-8520/8521 Series Rev.7.4_10

Seiko Instruments Inc.

(26) (27)

Vrip−VIN

S-8520D50MC(COUT:47 µF×2)

120

160

200

240

2 4 6 8 10 12 14 16

VIN(V)

Vrip

(mV)

IOUT=100 mA

IOUT=500 mA

IOUT=0.1 mA

Vrip−VIN

S-8521D50MC(COUT:47 µF×2)

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

(28) (29)

Vrip−VIN

S-8520B50MC(COUT:22 µF×2)

120

160

200

240

246810121416

VIN(V)

Vrip

(mV) IOUT=0.1 mA

IOUT=100 mA

IOUT=500 mA

Vrip−VIN

S-8521B50MC(COUT:22 µF×2)

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

(30) (31)

Vrip−VIN

S-8520F50MC(COUT:22 µF)

120

160

200

240

2 4 6 8 10 12 14 16

VIN(V)

Vrip

(mV)

IOUT=100 mA

IOUT=500 mA

IOUT=0.1 mA

Vrip−VIN

S-8521F50MC(COUT:22 µF)

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

PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers

Rev.7.4_10 S-8520/8521 Series

Seiko Instruments Inc. 33

3. PWM/PFM

(5) (7)

S-8521D30MC

PWM/PFM switching characteristics

1 10 100 1000

IOUT (mA)

VIN

(V)

S-8521B30MC

PWM/PFM switching characteristics

1 10 100 1000

IOUT (mA)

VIN

(V)

(9) (15)

S-8521F33MC

PWM/PFM switching characteristics

1 10 100 1000

IOUT (mA)

VIN

(V)

S-8521D50MC

PWM/PFM switching characteristics

1 10 100 1000

IOUT (mA)

VIN

(V)

(17) (19)

S-8521B50MC

PWM/PFM switching characteristics

1 10 100 1000

IOUT (mA)

VIN

(V)

S-8521F50MC

PWM/PFM switching characteristics

1 10 100 1000

IOUT (mA)

VIN

(V)

l Reel Specifications

l Tape Specifications

l Dimensions

n SOT-23-5 MP005-A 010907

Unit : mm

2.9±0.2

1.9±0.2

0.95±0.1

0.4±0.1

0.16 +0.1

-0.06

123

No. MP005-A-P-SD-1.1

No. : MP005-A-C-SD-1.0

ø1.5+0.1

-0 2.0±0.05

4.0±0.1(10-pitches total: 40.0±0.2)

ø1.0+0.1

-0

4.0±0.1 1.4±0.2

0.27±0.05

3.25±0.15

3°max.

Feed direction

12.5max.

9.0±0.3

ø13±0.2

(60°) (60°)

-3

ø180

ø60

-0

2±0.2

No. MP005-A-R-SD-1 0

3000 pcs./reel

Winding core

•

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.