S-8520/8521 Series
www.sii-ic.com
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE
SWITCHING REGULATOR CONTROLLER
© Seiko Instruments Inc., 1997-2010 Rev.9.0_00
Seiko Instruments Inc. 1
The S-8520/85 21 Series is a CMOS step-down s witching regulat or-controller with PWM control (S-8520 Series) and PWM
/ PFM switching control (S-8521 Ser ies). The S-8520/8521 Series has a reference v oltage source, an oscillation c ircuit, an
error amplifier, and ot her c om ponents.
The S-8520 Series provi des low-ripple p ower, high efficiency, and exc ellent transient characteristic s due to a PWM control
circuit capable of varying the duty ratio linearly from 0% up to 100%. The S-8520/8521 Series also has a soft-start circuit
that prevents overshoot at startup.
The S-8521 Series works with either PWM control or PFM control. It normally o perates using PWM control with a duty ratio
of 25% to 100%, but under a light load, it automatic ally switches to PFM control with a duty rati o of 25%. The S-8520/8 521
Series ensures high efficiency over a wide range of conditions for dev ices, from the standby mode to the operation.
By adding external Pch power MOS FET or PNP transistor, coil, capacitor, and externally connected diode, the
S-8520/8521 Series can function as a step-down switching regulator, and is ideal for power supply units of portable
devices due to smal l SOT -23-5 and t he feat ur e of lo w current co nsumption. It is also i deal for A C adapters due to the i nput
voltage up to 16 V.
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 V to 16 V (B, D, F types)
2.5 V to 10 V (A, C, E types)
• Output voltage: Selectable between 1.5 V a nd 6.0 V in 0.1 V step
• Duty ratio: 0% to 100% PWM control (S-8520 Ser ies)
25% to100% PWM / PFM s witching control ( S-85 21 Series)
• External parts are Pch po wer MOS FET or PNP transistor , coil, di ode, a nd capac itor o nly
(When using PNP transistor, add bas e resis tor and c apacit or).
• Oscillation frequenc y: 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 functio n
• With a built-in overload prote ction circ uit Overload detection time: 4 ms. typ. (A type)
14 ms. typ. (C type)
2.6 ms. typ. (E type)
• Lead-free, Sn 100%, halo gen -free*1
*1. Refer to “ Product Name Structure” for details.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
2
Applications
• On-board power supplies of battery devic es for mobile p hone, e lectroni c notebook s, PDAs.
• Power supplies for audio equ ipment, incl udi ng portab le C D pla yers and headp hone ste reo e quipm ent.
• Fixed voltage po wer suppl y for cameras, vi deo and comm unic ation d evices.
• Power supplies for microcomputers
• Conversion from NiH or four NiC d cel ls or t wo lithium -io n cells to 3.3 V / 3 V.
• Conversion of AC adapter inp ut to 5 V / 3 V.
Package
• SOT-23-5
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 3
Block Diagrams
1. S-8520 Series
VOUT
VSS
L
SD COUT
VON/OFF
______
+
VIN
Tr
EXT
VIN CIN
+
Oscillation
circuit
PWM control
circuit
Reference voltage
source with soft-start
−
+
ON/OFF
______
Remark Al l the d iodes i n the figur e ar e parasitic d iodes.
Figure 1
2. S-8521 Series
VOUT
VSS
L
SD COUT
+
VIN
Tr
EXT
VIN CIN
+
−
+
VON/OFF
______
ON/OFF
______
Oscillation
circuit
PWM / PFM switching
control circuit
Reference voltage
source with soft-start
Remark Al l t he d io des i n t h e f igur e are parasitic di odes.
Figure 2
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
4
Product Name Structure
The control types, pro duct types, and output voltage for the S-8520/8521 Series can be selected at the user’s request.
Please refer to the “1. Product name” for the definition of the product name, “2. Package” regarding the package
drawings and “3. Product name list” for the full product names.
1. Product name
S-852 x x xx MC − xxx T2 x
Environm ental code
U: Lead-free (Sn 100% ), halogen-free
G : Le ad-free (for details, ple ase contact our sales o ffice)
IC d irec tio n in ta p e s p ec ific a t io n s *1
Product nam e (abbreviation)*2
Package nam e (abbreviation)
MC : SOT-23-5
O utput voltage
15 to 60
(W hen the outp ut voltage is 1 .5 V, it is expressed as 15.)
Product type
A : O s cillat io n f re q ue n c y o f 1 8 0 k H z ,
W ith ove rload protection circuit
B: O scillation freq uency of 1 80 kH z,
W ithout overload p rotection circuit
C: O scillation frequency of 60 kHz,
W ith ove rload protection circuit
D: O scillation frequency of 60 kHz,
W ithout overload p rotection circuit
E: O scillation frequency of 300 kH z,
W ith ove rload protection circuit
F: Oscillatio n frequency of 300 kH z,
Without overloa d protection circuit
C ontrol system
0: PWM control
1: PWM / PFM switching control
*1. Refer to the tape specifications.
*2. Refer to “3. Product name list”.
2. Package
Drawing code
Package Name Package Tape Reel
SOT-23-5 MP005-A-P-SD MP005-A-C-SD MP005-A-R-SD
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 5
3. Product name list
3. 1 S-8520 Series Table 1 (1 / 2)
Output voltage [ V] S-8520AxxMC Series S-8520BxxMC Series S-8520CxxMC Series
1.5 − S-8520B15MC -ARAT2x −
1.8 − S-8520B18MC -ARDT2x −
2.0 S-8520A20MC-AVFT2x − −
2.1 S-8520A21MC-AVGT2x − −
2.4 − S-8520B24MC-ARJT2x −
2.5 S-8520A25MC-AVKT2x S-8520B25MC-ARKT2x S-8520C25MC-BRKT2x
2.6 S-8520A26MC-AVLT2x − −
2.7 S-8520A27MC-AVMT2x S-8520B27MC-ARMT2x S-8520C27MC-BRMT2x
2.8 S-8520A28MC-AVNT2x S-8520B28MC-ARNT2x S-8520C28MC-BRNT2x
2.9 S-8520A29MC-AVOT2x S-8520B29MC-AROT2x S-8520C29MC-BROT2x
3.0 S-8520A30MC-AVPT2x S-8520B30MC-ARPT2x S-8520C30MC-BRPT2x
3.1 S-8520A31MC-AVQT2x S-8520B31MC-ARQT2x S-8520C31MC-BRQT2x
3.2 S-8520A32MC-AVRT2x S-8520B32MC-ARRT2x S-8520C32MC-BRRT2x
3.3 S-8520A33MC-AVST2x S-8520B33MC-ARST2x S-8520C33MC-BRST2x
3.4 S-8520A34MC-AVTT2x S-8520B34MC-ARTT2x S-8520C34MC-BRTT2x
3.5 S-8520A35MC-AVUT2x S-8520B35MC-ARUT2x S-8520C35MC-BRUT2x
3.6 S-8520A36MC-AVVT2x S-8520B36MC-ARVT2x S-8520C36MC-BRVT2x
4.0 − S-8520B40MC- ARZT2x −
4.3 − S-8520B43MC -ASCT2x −
5.0 S-8520A50MC-AWJT2x S-8520B50MC-ASJT2x S-8520C50MC-BSJT2x
5.3 − S-8520B53MC -ASMT2x −
Table 1 (2 / 2)
Output voltage [ V] S-8520DxxMC Series S-8520ExxMC Series S-85 20F xxMC Serie s
1.5 − S-8520E15MC-BJAT2x S-8520F15MC-BNAT2x
1.6 − S-8520E16MC-BJBT2x −
1.8 − S-8520E18MC-BJDT2x S-8520F18MC-BNDT2x
2.0 − − S-8520F20MC-BNFT2x
2.5 S-8520D25MC-BVKT2x S-8520E25MC-BJKT2x S-8520F25MC-BNKT2x
2.6 − − S-8520F26MC-BNLT2x
2.7 S-8520D27MC-BVMT2x − S-8520F27MC-BNMT2x
2.8 S-8520D28MC-BVNT2x S-8520E28MC-BJNT2x S-8520F28MC-BNNT2x
2.9 S-8520D29MC-BVOT2x − −
3.0 S-8520D30MC-BVPT2x S-8520E30MC-BJPT2x S-8520F30MC-BNPT2x
3.1 S-8520D31MC-BVQT2x − S-8520F31MC-BNQT2x
3.2 S-8520D32MC-BVRT2x − −
3.3 S-8520D33MC-BVST2x S-8520E33MC-BJST2x S-8520F33MC-BNST2x
3.4 S-8520D34MC-BVTT2x − S-8520F34MC-BNTT2x
3.5 S-8520D35MC-BVUT2x − S-8520F35MC-BNUT2x
3.6 S-8520D36MC-BVVT2x − S-8520F36MC-BNVT2x
4.0 − − S-8520F40MC-BNZT2x
4.5 − − S-8520F45MC-BOET2x
5.0 S-8520D50MC-BWJT2x S-8520E50MC-BKJT2x S-8520F50MC-BOJT2x
5.2 − S-8520E52MC -BKLT2x −
5.5 − − S-8520F55MC-BOOT2x
6.0 − − S-8520F60MC-BOTT2x
Remark 1. Please contact our sales of fi c e for pro ducts with o ut put v oltage other th an t hose sp ecif i ed ab ove.
2. x: G or U
3. Please se lect prod uct s of en vironm ental code = U for Sn 100 %, ha lo gen -f r ee pr odu cts.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
6
3. 2 S-8521 Series Table 2 (1 / 2)
Output voltage [V] S-8521AxxMC Series S-8521BxxMC Series S-8521CxxMC Series
1.5 − S-8521B15MC-ATAT2x −
1.6 − − S-8521C16MC-BTBT2x
1.8 − S-8521B18MC-ATDT2x −
1.9 − S-8521B19MC-ATET2x −
2.0 − S-8521B20MC-ATFT2x −
2.1 − S-8521B21MC-ATGT2x −
2.3 − S-8521B23MC-ATIT2x −
2.5 S-8521A25MC-AXKT2x S-8521B25MC-ATKT2x S-8521C25MC-BTKT2x
2.6 − S-8521B26MC-ATLT2x −
2.7 S-8521A27MC-AXMT2x S-8521B27MC-ATMT2x S-8521C27MC-BTMT2x
2.8 S-8521A28MC-AXNT2x S-8521B28MC-ATNT2x S-8521C28MC-BTNT2x
2.9 S-8521A29MC-AXOT2x S-8521B29MC-ATOT2x S-8521C29MC-BTOT2x
3.0 S-8521A30MC-AXPT2x S-8521B30MC-ATPT2x S-8521C30MC-BTPT2x
3.1 S-8521A31MC-AXQT2x S-8521B31MC-ATQT2x S-8521C31MC-BTQT2x
3.2 S-8521A32MC-AXRT2x S-8521B32MC-ATRT2x S-8521C32MC-BTRT2x
3.3 S-8521A33MC-AXST2x S-8521B33MC-ATST2x S-8521C33MC-BTST2x
3.4 S-8521A34MC-AXTT2x S-8521B34MC-ATTT2x S-8521C34MC-BTTT2x
3.5 S-8521A35MC-AXUT2x S-8521B35MC-ATUT2x S-8521C35MC-BTUT2x
3.6 S-8521A36MC-AXVT2x S-8521B36MC-ATVT2x S-8521C36MC-BTVT2x
4.0 − S-8521B40MC-ATZT2x −
4.4 − S-8521B44MC-AUDT2x −
5.0 S-8521A50MC-AYJT2x S-8521B50MC-AUJT2x S-8521C50MC-BUJT2x
5.1 − S-8521B51MC-AUKT2x −
5.3 − S-8521B53MC-AUMT2x −
6.0 − S-8521B60MC-AUTT2x −
Table 2 (2 / 2)
Output voltage [V] S-8521DxxMC Series S-85 21E xxM C Serie s S-85 21F xxMC Serie s
1.5 − S-8521E15MC-BLAT2x S-8521F15MC-BPAT2x
1.6 S-8521D16MC-BXBT2x S-8521E16MC-BLBT2x −
1.7 − S-8521E17MC-BLCT2x −
1.8 S-8521D18MC-BXDT2x S-8521E18MC-BLDT2x S-8521F18MC-BPDT2x
1.9 − S-8521E19MC-BLET2x S-8521F19MC-BPET2x
2.0 S-8521D20MC-BXFT2x S-8521E20MC-BLFT2x −
2.1 S-8521D21MC-BXGT2x − −
2.2 S-8521D22MC-BXHT2x S-8521E22MC-BLHT2x −
2.5 S-8521D25MC-BXKT2x S-8521E25MC-BLKT2x S-8521F25MC-BPKT2x
2.7 S-8521D27MC-BXMT2x − −
2.8 S-8521D28MC-BXNT2x − −
2.9 S-8521D29MC-BXOT2x − −
3.0 S-8521D30MC-BXPT2x S-8521E30MC-BLPT2x S-8521F30MC-BPPT2x
3.1 S-8521D31MC-BXQT2x − −
3.2 S-8521D32MC-BXRT2x − S-8521F32MC-BPRT2x
3.3 S-8521D33MC-BXST2x S-8521E33MC-BLST2x S-8521F33MC-BPST2x
3.4 S-8521D34MC-BXTT2x － S-8521F34MC-BPTT2x
3.5 S-8521D35MC-BXUT2x S-8521E35MC-BLUT2x −
3.6 S-8521D36MC-BXVT2x − S-8521F36MC-BPVT2x
4.0 S-8521D40MC-BXZT2x − S-8521F40MC-BPZT2x
4.2 − S-8521E42MC-BMBT2x −
4.5 S-8521D45MC-BYET2x − −
5.0 S-8521D50MC-BYJT2x S-8521E50MC-BMJT2x S-8521F50MC-BQJT2x
5.2 S-8521D52MC-BYLT2x − −
5.3 − S-8521E53MC-BMMT2x −
5.5 S-8521D55MC-BYOT2x − S-8521F55MC-BQOT2x
Remark 1. Please contact our sales office for pro ducts with output volt age other than those sp ecifie d above.
2. x: G or U
3. Please select prod ucts of en vironm ent al code = U for Sn 100 %, halo gen -free pr odu cts.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 7
Pin Configuration
Table 3
Pin No. Symbol Description
1
ON/OFF
______
Shutdown pin
“H”: Normal operation
(Step-down operation)
“L”: Stop step-down operation
(All circuits stop)
2 VSS GND pin
3 VOUT Output voltag e monitor ing pi n
4 EXT Connection pin for external transist or
5 VIN IC power supply pin
5 4
1 3 2
SOT-23-5
Top view
Figure 3
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
8
Absolute Maximum Ratings
Table 4
(Ta = +25°C unless other wise specified)
Item Symbol Absolute maximum rating Unit
A, C, E types VSS − 0.3 to VSS + 12.0 V
VIN pin voltage B, D, F types VIN VSS − 0.3 to VSS + 18.0 V
A, C, E types VSS − 0.3 to VSS + 12.0 V
VOUT pin voltage B, D, F types VOUT VSS − 0.3 to VSS + 18.0 V
A, C, E types VSS − 0.3 to VSS + 12.0 V
ON/OFF
______
pin voltage B, D, F types VON/OFF
______
VSS − 0.3 to VSS + 18.0 V
EXT pin voltage VEXT V
SS − 0.3 to VIN + 0.3 V
EXT pin current IEXT ±50 mA
250 (When not mounte d on b oard) mW
Power dissipation PD 600*1 mW
Operating ambient temperature Topr −40 to +85 °C
Storage temperature Tstg −40 to +125 °C
*1. When mounted on board
[Mounted board]
(1) Board size : 114.3 mm × 76.2 mm × t1.6 mm
(2) Board name : JEDEC ST ANDARD51- 7
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.
(1) When mounted on board (2) When not mounted on board
0 50 100 150
400
200
0
Power Dissipation (P
D
) [mW]
500
300
100
600
700
Ambient Temperature (Ta) [°C]
050 100 150
200
100
0
250
150
50
300
Ambient Temperature (Ta) [°C]
Power Dissipation (P
D
) [mW]
Figure 4 Pow er Dissipation of Package
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 9
Electrical Characteristics
1. A type, B type
Table 5 (Ta = +25°C unless other wise specified)
Item Symbol Conditions Min. Typ. Max. Unit Test
Circuit
Output voltage*1 VOUT(E) − VOUT(S)
× 0.976 VOUT(S) VOUT(S)
× 1.024 V 3
A type 2.5 − 10.0 V 2
Input voltage VIN − B type 2.5 − 16.0 V 2
Current consumption 1 ISS1 V
OUT = VOUT(S) × 1.2 − 35 60 μA 2
Current consumption
during shutdown ISSS VON/OFF
______
= 0 V − − 0.5 μA 2
S-8520/8521x15 to 24 −2.3 −4.5 − mA −
S-8520/8521x25 to 34 −3.7 −7.0 − mA −
S-8520/8521x35 to 44 −5.3 −9.3 − mA −
S-8520/8521x45 to 54 −6.7 −11.3 − mA −
IEXTH V
EXT = VIN − 0.4 V
S-8520/8521x55 to 60 −8.0 −13.3 − mA −
S-8520/8521x15 to 24 +4.3 +8.4 − mA −
S-8520/8521x25 to 34 +7.0 +13.2 − mA −
S-8520/8521x35 to 44 +9.9 +17.5 − mA −
S-8520/8521x45 to 54 +12.6 +21.4 − mA −
EXT pin output current
IEXTL V
EXT = 0.4 V
S-8520/8521x55 to 60 +15.0 +25.1 − mA −
VOUT(S) ≤ 2.0 V VIN = 2.5 V to 2.94 V − 30 60 mV 3
Line regulation ΔVOUT1 VOUT(S) > 2.0 V VIN = VOUT(S) × 1.2 to 1.4 − 30 60 mV 3
Load regulatio n ΔVOUT2 Load curr ent = 10 μA to IOUT × 1.25 − 30 60 mV 3
Output voltage
temperature coefficient ΔVOUT
ΔTa Ta = −40°C to +85°C − ±VOUT(S)
× 5E − 5 − V/°C 3
VOUT(S) ≤ 2.4 V 144 180 216 kHz 3
Oscillation frequenc y fosc Measure waveform at
EXT pin. VOUT(S) ≥ 2.5 V 153 180 207 kHz 3
PWM / PFM control
switching duty ratio
(S-8521 Series) PFMDuty No load, measure waveform at EXT pin. 15 25 40 % 3
VSH Determine oscillation at EXT pin 1.8 − − V 2
ON/OFF
______
pin
input voltage VSL Determ ine osci llation sto p at EXT pin − − 0.3 V 2
ISH − −0.1 − 0.1 μA 1
ON/OFF
______
pin
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
(A type) tpro Time until the EXT pin reaches VIN after
dropping VOUT to 0 V. 2.0 4.0 8.0 ms 2
Efficiency EFFI − − 93 − % 3
External parts Coil: Sumida Corporation CD54 ( 47 μH)
Diode: Matsushita Electric Industr ial Co., Ltd. MA720 (Shottk y t y pe)
Capacitor: Matsushita Electric Industrial Co., Ltd. T E (16 V, 22 μF tantalum t ype)
Transistor: Toshiba Corporation 2SA1213
Base resistance (Rb): 0.68 kΩ
Base capacitor (Cb): 2200 pF (Ceramic type)
Unless otherwise indicated, connect the recommended components to the IC. When VIN = VOUT(S) × 1.2 V (VIN = 2.5 V
when VOUT(S) ≤ 2.0 V), IOUT = 120 mA, connect the ON/OFF
______
pin to the VIN pi n.
*1. VOUT(S): Specified output voltage value, VOUT(E): Actual output voltage value
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
10
2. C type, D type
Table 6 (Ta = +25°C unless other wise specified)
Item Symbol Conditions Min. Typ. Max. Unit Test
Circuit
Output voltage*1 VOUT(E) − VOUT(S)
× 0.976 VOUT(S) VOUT(S)
× 1.024 V 3
C type 2.5 − 10.0 V 2
Input voltage VIN − D type 2.5 − 16.0 V 2
Current consumption 1 ISS1 V
OUT = VOUT(S) × 1.2 − 10 21 μA 2
Current consumption
during shutdown ISSS VON/OFF
______
= 0 V − − 0.5 μA 2
S-8520/8521x15 to 24 −2.3 −4.5 − mA −
S-8520/8521x25 to 34 −3.7 −7.0 − mA −
S-8520/8521x35 to 44 −5.3 −9.3 − mA −
S-8520/8521x45 to 54 −6.7 −11.3 − mA −
IEXTH V
EXT = VIN − 0.4 V
S-8520/8521x55 to 60 −8.0 −13.3 − mA −
S-8520/8521x15 to 24 +4.3 +8.4 − mA −
S-8520/8521x25 to 34 +7.0 +13.2 − mA −
S-8520/8521x35 to 44 +9.9 +17.5 − mA −
S-8520/8521x45 to 54 +12.6 +21.4 − mA −
EXT pin output current
IEXTL V
EXT = 0.4 V
S-8520/8521x55 to 60 +15.0 +25.1 − mA −
VOUT(S) ≤ 2.0 V VIN = 2.5 V to 2.94 V − 30 60 mV 3
Line regulation ΔVOUT1 VOUT(S) > 2.0 V VIN = VOUT(S) × 1.2 to 1.4 − 30 60 mV 3
Load regulatio n ΔVOUT2 Load curr ent = 10 μA to IOUT × 1.25 − 30 60 mV 3
Output voltage
temperature coefficient ΔVOUT
ΔTa Ta = −40°C to +85°C − ±VOUT(S)
× 5E − 5 − V/°C 3
VOUT(S) ≤ 2.4 V 45 60 75 kHz 3
Oscillation frequenc y fosc Measure waveform at
EXT pin. VOUT(S) ≥ 2.5 V 48 60 72 kHz 3
PWM / PFM control
switching duty ratio
(S-8521 Series) PFMDuty No load, measured waveform at EXT pin. 15 25 40 % 3
VSH Determine oscillation at EXT pin 1.8 − − V 2
ON/OFF
______
pin
input voltage VSL Determ ine osci llation sto p at EXT pin − − 0.3 V 2
ISH − −0.1 − 0.1 μA 1
ON/OFF
______
pin
input leakage current ISL − −0.1 − 0.1 μA 1
Soft start time tss − 6.0 12.0 24.0 ms 3
Overload detection time
(C type) tpro Time until the EXT pin reaches VIN after
dropping VOUT to 0 V. 7.0 14.0 28.0 ms 2
Efficiency EFFI − − 93 − % 3
External parts Coil: Sumida Corporation CD54 ( 47 μH)
Diode: Matsushita Electric Industr ial Co., Ltd. MA720 (Shottk y t y pe)
Capacitor: Matsushita Electric Industrial Co., Ltd. T E (16 V, 22 μF tantalum t ype)
Transistor: Toshiba Corporation 2SA1213
Base resistance (Rb): 0.68 kΩ
Base capacitor (Cb): 2200 pF (Ceramic type)
Unless otherwise indicated, connect the recommended components to the IC. When VIN = VOUT(S) × 1.2 V (VIN = 2.5 V
when VOUT(S) ≤ 2.0 V), IOUT = 120 mA, connect the ON/OFF
______
pin to the VIN pi n.
*1. VOUT(S): Specified output voltage value, VOUT(E): Actual output voltage value
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 11
3. E type, F type
Table 7 (Ta = +25°C unless other wise specified)
Item Symbol Conditions Min. Typ. Max. Unit Test
Circuit
Output voltage*1 VOUT(E) − VOUT(S)
× 0.976 VOUT(S) VOUT(S)
× 1.024 V 3
E type 2.5 − 10.0 V 2
Input voltage VIN − F type 2.5 − 16.0 V 2
Current consumption 1 ISS1 V
OUT = VOUT(S) × 1.2 − 60 100 μA 2
Current consumption
during shutdown ISSS VON/OFF
______
= 0 V − − 0.5 μA 2
S-8520/8521x15 to 24 −2.3 −4.5 − mA −
S-8520/8521x25 to 34 −3.7 −7.0 − mA −
S-8520/8521x35 to 44 −5.3 −9.3 − mA −
S-8520/8521x45 to 54 −6.7 −11.3 − mA −
IEXTH V
EXT = VIN − 0.4 V
S-8520/8521x55 to 60 −8.0 −13.3 − mA −
S-8520/8521x15 to 24 +4.3 +8.4 − mA −
S-8520/8521x25 to 34 +7.0 +13.2 − mA −
S-8520/8521x35 to 44 +9.9 +17.5 − mA −
S-8520/8521x45 to 54 +12.6 +21.4 − mA −
EXT pin output current
IEXTL V
EXT = 0.4 V
S-8520/8521x55 to 60 +15.0 +25.1 − mA −
VOUT(S) ≤ 2.0 V VIN = 2.5 V to 2.94 V − 30 60 mV 3
Line regulation ΔVOUT1 VOUT(S) > 2.0 V VIN = VOUT(S) × 1.2 to 1.4 − 30 60 mV 3
Load regulatio n ΔVOUT2 Load curr ent = 10 μA to IOUT × 1.25 − 30 60 mV 3
Output voltage
temperature coefficient ΔVOUT
ΔTa Ta = −40°C to +85°C − ±VOUT(S)
× 5E − 5 − V/°C 3
VOUT(S) ≤ 2.4 V 225 300 375 kHz 3
Oscillation frequenc y fosc Measure waveform at
EXT pin. VOUT(S) ≥ 2.5 V 240 300 360 kHz 3
PWM / PFM control
switching duty ratio
(S-8521 Series) PFMDuty No load, measure waveform at EXT pin. 15 25 40 % 3
VSH Determine oscillation at EXT pin 1.8 − − V 2
ON/OFF
______
pin
input voltage VSL Determ ine osci llation sto p at EXT pin − − 0.3 V 2
ISH − −0.1 − 0.1 μA 1
ON/OFF
______
pin
input leakage current ISL − −0.1 − 0.1 μA 1
Soft start time tss − 2.0 4.5 9.2 ms 3
Overload detection time
(E type) tpro Time until the EXT pin reaches VIN after
dropping VOUT to 0 V. 1.3 2.6 4.5 ms 2
Efficiency EFFI − − 90 − % 3
External parts Coil: Sumida Corporation CD54 ( 47 μH)
Diode: Matsushita Electric Industr ial Co., Ltd. MA720 (Shottk y t y pe)
Capacitor: Matsushita Electric Industrial Co., Ltd. T E (16 V, 22 μF tantalum t ype)
Transistor: Toshiba Corporation 2SA1213
Base resistance (Rb): 0.68 kΩ
Base capacitor (Cb): 2200 pF (Ceramic type)
Unless otherwise indicated, connect the recommended components to the IC. When VIN = VOUT(S) × 1.2 V (VIN = 2.5 V
when VOUT(S) ≤ 2.0 V), IOUT = 120 mA, connect the ON/OFF
______
pin to the VIN pi n.
*1. VOUT(S): Specified output voltage value, VOUT(E): Actual output voltage value
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
12
Test Circuit
1.
EXT
VSS
VOUT open
open
VIN
AON/OFF
_
_____
Figure 5
2.
VSS
VIN
−
+
VOUT
EXT
Osilloscope
A
ON/OFF
_
_____
Figure 6
3.
VSS
0.68 k Ω 2200 pF
VIN
− V
+
VOUT
EXT
−
+
ON/OFF
_
_____
Figure 7
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 13
Operation
1. Switching control method
1. 1 PWM control (S-8520 Series)
The S-8520 Series is a DC-DC converter using a pulse width modulation method (PWM) and features a low
current consumption.
In conventional PFM DC-DC converters, pulses are skipped when the output load current is low, causing a
fluctuation in the ri ppl e frequ enc y of the out put voltage, resulti ng in an in creas e in the ri ppl e volt age.
The switching frequency does not change, although the pulse width changes from 0 to 100% corresponding to
each load current. The ripple voltage generated from switching can thus be removed easily through a filter
because the switching frequency is constant. And the ripple voltage will be skipped to be low current
consumption when the p uls e width is 0% or it is no loa d, input curr ent vo ltage is hi gh.
1. 2 PWM / PFM switching control (S-8521 Seri es)
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% in a high
output load current area.
The S-8521 Series ope rates under PFM control with the pulse widt h duty fixed at 25%, and pulses are skipp ed
according to the load current. The oscillation circuit thus oscillate s intermittently so that the r esultant lower self
current consumption prevent s a reduction in the efficiency at a low load current. T he switching point from PWM
control to PFM control depends on the external devices (coil, diode, etc.), input voltage and output voltage.
The S-8521 Series is an es pe ciall y highl y efficie nt DC-DC c onver ter at an output curre nt around 10 0 μA.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
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2. Soft start function
The S-8520/8521 Series has a built-in soft start-circuit. This circuit enables the output voltage (VOUT) to rise
gradually over the specified soft start time (t), when power-on or when the ON/OFF
______
pin is at the “H” level. This
prevents the output voltag e from oversho oting.
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, Perform sufficient
evaluation with actual dev ice f or desig n.
S-8520A33MC (VIN: 0 V→4.0 V)
t [1 ms/div]
VOUT
[1 V/div]
Rush current
[0.5 A/div]
0 A
1.5 A
3 V
0 V
Figure 8 Waveforms o f ou tpu t voltage and rush curre nt at so ft start
3. ON/OFF
_______
pin (Shutdown pin)
The ON/OF F
______
pi n stops or starts st ep-u p oper ation.
Setting the ON/OFF
______
pin to the “L” level stops operation of all the internal circ uits and reduces current consumption
significantly. The EXT pin’s v olta ge is s et to the VIN voltage level so that the switching transistor is turned off.
Do not use the ON/OFF
______
pin in a floating state because it has t he structure shown in Figure 9 and is not pulled up
or pulled do wn internally. Do not apply a v oltage of between 0.3 V an d 1.8 V to the ON/OFF
______
pin because applyi ng
such a voltage increases the current cons um ption. W hen not usi ng th e ON/O FF
______
pin, co nnect it to the VIN pin.
Table 8
ON/OFF
______
pin CR Oscillation Circuit Output voltage
“H” Operation Set value
“L” Stop VSS
VIN
VSS
ON/OFF
_
_____
Figure 9
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 15
4. Overload protection circuit (A, C, E types)
The A, C and E types of the S-8520/8 521 Series hav e a b uilt-in ov erl oad protecti on circ uit.
If the output voltage drops under the overload status, the maximum duty status (100%) c ontinues. If this 100% dut y
status lasts longer than the overload detection time (tpro), the circuit keeps the EXT pin at “H” to protect the
switching transistor and inductor. When the overload protection circuit is functioning, the soft start works in the IC
for the reference volt age, and the reference voltag e rises slowly from 0 V. T he reference voltage and the feedback
voltage obtained by div iding the output voltage are compared to each other. While the reference volt age is low, the
EXT pin keeps “H” and o scillation sto ps. If the reference vo ltage ris es and e xceeds the feedb ack voltage, oscil lation
restarts.
After oscillation is restarted, if a load is heavy and the EXT pin keeps the “L” level longer than the overload
detection time (tpro), the circuit operates again, and the IC enters the intermittent operation mode by repeating the
action described above. Once the overload state is off, the IC restarts the normal operation.
Waveforms
at EXT pin
Protection circuit ON
[tss × 0.3]
Overload detection time (tpro)
Figure 10 Waveforms at EXT pin when the overload protection circuit operates
5. 100% duty cycle
The S-8520/8521 Ser ies operates with a maximum dut y cycle of 100%. When u sing the B, D and F types pr oducts,
which do not have the overload protectio n circuit, the switching tra nsistor keeps ON continu ally to supply current to
the load, even in cas es where the input voltage dro ps to the set value of outp ut voltage or less. The output voltage
in this case is; the voltage subtracting both of the ind uctance’s DC resistance and the v oltage drop by the switching
resistor’s ON-resistance, from the in put vol tage.
The A, C and E types that have the overload protection circuit cannot be used for continually supplying current to
the load, as described above, because thes e types enter the int ermittent oper ation mode by the overlo ad protection
circuit’s operation, when 100% duty lasts longer than the overl oad d etect ion tim e (tpro).
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
16
Selection of Products and External Parts
1. Method for selecting series products
The S-8520/8521 S eries is c lassifi ed into 12 types, acco rdi ng to the c ontrol s ystems (PW M control and PW M / PFM
switching control), the different oscillation frequencies, and set-up of an overload protection circuit. Please select
the type for your ap plicati on accor ding to th e foll o wing feat ures.
1. 1 Control systems
Two different control systems are available: PWM control system (S-8520 Series) and PWM / PFM switching
control system (S-8521 Ser ies).
For applications for which the load current greatl y differs between standby and ope ration, if the efficiency during
standby is important, applying the PWM/PFM switching system (S-8321 Series) realizes high efficiency during
standby.
For applications for which s witching noise is critical, applying the PWM control s ystem (S-8320 Series) whereb y
switching frequency does not change due to load current allows the ripple voltage to be easily suppressed by
using a filter.
1. 2 Oscillation frequencies
Either oscillation fre quency, 180 kHz (A an d B types), 60 kHz (C and D t ypes), or 300 kHz (E and F t ypes), can
be selected.
The A, B, E and F types have high oscillation frequency, how ripple voltage and excellent transient response
characteristics. A small inductance can be used for these types because the peak current is low when inducing
the same load current. Use of small o utput capac itors is effective for do wnsizing devi ces.
The C and D types, whereby lower oscillation frequency realizes smaller self-consumption current, are highly
efficient under light loads. In particular, the D t ype, when combined with a PWM/PFM switching control system,
drastically improves the op erat ion effic ienc y when the output load curr ent is appro ximate ly 100 mA.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 17
1. 3 Overload protection circuit
Types are selectable the S-8520/8521 Series with the overload protection circuit (A, C and E types) or without
the overload pr otection circ uit (B, D and F t ypes).
By the S-8520/8521 Series with the overload protection circuit (A, C and E types), the switching components
and inductor can be prot ected because the overload protec tion circuit works and is set to the intermitte nt mode,
in case of overload or load short-circuit.
But in case of supplying current to load by using 100% duty cycle, select the S-8520/8521 Series without the
overload protection circ uit (B, D and F t ypes ), according t o the co ndit ions of app lic ation.
The operation voltage differs in 10 V (A, B and E types) or 16 V (B, D and F types) whether the overload
protection circuit is avail able or not.
Table 9 shows items for selecting the type according to the requirements of application. Select it matching the
marks () for your requirement.
Table 9
S-8520 Series S-8521 Series
Item A B C D E F A B C D E F
The need of overlo ad protect ion circ uit
Input voltage exceeds 10 V
Focusing on efficiency of light load status
(1 mA or less)
Using with middle load current (about 200
mA)
Using with large lo ad curr ent (about 1 A)
Focusing on the lo w ripple volt age
Focusing on do wnsizing exte rnal parts
Remark : Indispensable condition
: Superiority of requirem ent
: Particularly superiority of requirement
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
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2. Inductor
The inductanc e value (L v al ue) has a stron g influ enc e on t he maximum o utput curr ent (IOUT) and efficiency (η).
The peak current (IPK) increases b y decreasing L valu e and the stabilit y of the circuit i mproves and IOUT increases. If
L value is decreased, the efficienc y fa lls causing a decline in the current drive capacit y for the switching transistor,
and IOUT decreases.
The loss of IPK by the switching transistor decreases by increasing L and the efficiency becomes the maximum at a
certain L value. Further increasing L value decreases the efficiency due to the loss of the direct current resistance
of the coil. IOUT also decreases.
For the S-8520/8521 Series, increasing the inductance value, the output voltage may be unstable in some cases,
depending on t he conditions of the i nput voltage, output vo ltage, and the load current. Perform suffic ient evaluation
under the actual condit ion an d dec ide an op timum induct a nce va lue.
The recommended in ductanc es are 47 μH for A, B, C, D t ypes and 2 2 μH for E, F types.
Be careful of the allowable inductor current when choosing an inductor. Exceeding the allowable current of the
inductor causes magnetic saturation, muc h lower efficiency and destruction of the IC chip due to a larg e current.
Choose an inductor so that IPK does not exceed the allowable current. IPK in continuous mode is calculated by the
following equation:
IPK = IOUT + (VOUT + VF*2 ) × (VIN − VOUT)
2 × fosc*1 × L × (VIN + VF*2)
*1. f
osc: Oscillation frequency
*2. V
F: Forward voltage of the dio de
3. Diode
Use an external diode that m eets the fo llowing requirements :
• Its forward voltage is lo w (Schottky barrie r diode is r eco mmended).
• Its switching speed is high (50 ns m ax.).
• Its reverse direction voltage is higher th an VIN.
• Its current rating is higher than IPK.
4. Capacitors (CIN, COUT)
A capacitor for the input (CIN) improves efficienc y by reducing power impedance an d stabilizing the input current .
Select the CIN value according to impedance of the power supply to be used. Approximately 47 to 100 μF is
recommended for the capacit or de pe nding o n imped ance o f the po wer source and l oad current valu e.
For a capacitor for output (CL), select a large capacitance with low ESR (Equivalent Series Resistance) for
smoothing the ripple v oltage. Ho wever, capacitor with extre mely sm all ES R such as cera mic capacitor ( about 0. 3
Ω or less) may destabilize the output voltage, according to the conditions of input and output voltages. A
tantalum electrolyte ca pacitor is recomm en ded. 47 μF to 100 μF is recom mend ed for the cap acitor.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 19
5. External transistor
Enhancement (Pch) MOS FET or bipolar (P NP) MOS FET can be used fo r ext ernal tran sistor.
5. 1 Enhancement (Pch) MOS FET type
The EXT pin of the S-8520/8521 Series is capable of directly driving a Pch MOS FET with a gate capacity
around 1000 pF.
When using a Pch MOS FET, 2 to 3% higher efficiency is provided because its switching speed is faster and it
does not cause po wer dissipation, compare d to PNP bipol ar transistors.
The important parameters in selecting MOS FETs are the threshold voltage, the breakdown voltage between
gate and source, the breakdown voltage between drain and source, the total gate capacity, the on-resistance,
and the current ratings.
The EXT pin swings from voltages between VIN to VSS. If the input voltage is low, use a MOS FET with the low
threshold voltage. If the input voltage is high, use a MOS FET having the breakdown voltage between gate and
source higher several vo lts than the input vo ltag e.
Immediately after the po wer-on or power-of f (stopping the step-do wn operation), the input voltage will be applied
between drain and source of the MOS FET. Use the breakdown voltage between drain and source also higher
several volts than the in put voltag e.
The total gate capacit y and t he o n-resistan ce affect efficie nc y.
Power dissipation when charging and discharging the gate capacity by switching operation affects efficiency, in
the area of low load current, as the total gate capacity is larger and the input voltage is higher. Select a MOS
FET with a small total gate capac it y for efficienc y at light l oad.
In the area of large l oad current, efficienc y is affected by po wer dissipatio n caused by MO S FET’s on-resistance .
For efficiency at large load, s elect a MOS F ET having as low on-resistance as possible.
As for the current rating, select a MOS FET having the maxim um contin uous dr ai n current ratin g high er than IPK.
For reference, this document has the data of efficiency. TM6201 by Toyota Industries Corporation for
applications with an input voltage of 10 V or less, IRF7606 by International Rectifier Corporation Japan for
applications with an input volt age over 10 V (Refer to “ Reference Dat a”).
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
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5. 2 Bipolar PNP type
Figure 11 shows the sample of circuit diagram using Toshiba Corporation 2SA1213 as the bipolar transistor
(PNP). The hFE value and th e Rb value of tha t bipolar trans istor determin e the driving ca pacity, which is used for
increasing the output current.
VIN EXT
VIN
Rb C
b
Toshiba Corpor ation
2SA1213
Figure 11
The Rb value is given b y the follo wing equat ion:
R
b = VIN − 0.7
Ib − 0.4
IEXTL
Calculate 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 increases the output current, but it also decreases efficiency. Determine the optimum value
through experiment, sinc e th e bas e curr ent may flo w on the pulse, or vo lt age m ay dr op due to wiring resistance.
In addition, if speed-u p capacitor Cb is connected in parallel with resistor R b, as shown in Figure 11, the loss in
switching will be reduced, le ading to hi gh er efficie nc y.
Determine the Cb value usi ng the following equatio n:
Cb ≤ 1
2 × π × Rb × fosc × 0.7
Select the Cb value after performin g sufficient ev aluation s ince t he optim um Cb value differs depending upon the
characteristics of the bipolar tr ansist or.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 21
Standard Circuits
1. Using a bipolar transistor
VSS
VOUT
+
VIN CIN
L
SD COUT
Reference voltage
source with soft start
VIN
Tr
Cb Rb
EXT +
+
−
PWM control or
PWM / PFM swi tching
control circuit
Oscillation
circuit
VON/OFF
______
ON/OFF
______
Figure 12
2. Using a Pch MOS FET transistor
VSS
VOUT
L
SD COUT
+
+
−
VIN
Tr
+
EXT
VIN CIN
Oscillation
circuit Reference voltage
source with soft start
PWM control or
PWM / PFM switching
control circuit
VON/OFF
______
ON/OFF
______
Figure 13
Caution The above connection diagram and constant will not guarantee successful operation. Perform
through evaluation using the actual application to set the constant.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
22
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 nois e 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 po wer suppl y used, fully ch e ck them using an act ual ly mounte d 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 al lo wable dissi pation of the switching tr ansist or and i nductor.
• Make sure that dissipation of the switching transistor (especially at a high temperature) does not exceed the
allowable dissipati on of th e packa ge.
• Do not apply a n electrostatic discharge to this IC that exceeds the perfor mance 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 by
products including this IC of patents owned by a third party.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 23
Application Circuits
1. External adjustment of output voltage
In the S-8550/8521 Series, by adding external resistors (RA, RB) and a capacitor (CFB), the output voltage can be
adjusted or be set freely in the range of 1.5 to 6.0 V, as sho wn in Figure 14. Temperature gradient can be given by
inserting a thermistor in s erie s to RA and RB.
S-8520/8521 Series
C
C
R
A
R
B
D1
VOUT
VSS
−
+
VIN
OUT
EXT
−
+
+
−
R
2
R
1
Oscillation
Circuit
PWM control or PWM /
PFM swi tchin g contr ol uni t
Reference volt age
source with soft start
ON/OFF
______
Figure 14
Caution The above connection diagram and constant will not guarantee 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 o f the parallel re sistance value of e xternal resistance (R B) and internal resistances (R1 + R2) of the IC,
to external resistance (RA). The output voltage is e xpresse d by the foll o wing equation:
OUT = VOUT + VOUT × RA ÷ (RB //*1(R1 + R2))
*1. // shows the combined resistance in parallel.
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 deviatio ns of internal res ista nces (R1 and R2) in the IC.
Let us designate the maximu m deviations o f the absol ute value of R A and RB by RA max. and RB max., respectively,
the minimum deviations by RA min. and RB min., 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 OUT min. and the maximum deviation value OUT max. of the OUT are expressed by the following
equations:
OUT min. = VOUT × 0.976 + VOUT × 0.976 × RA min. ÷ (RB max. // (R1 + R2) max.)
OUT max. = VOUT × 1.024 + VOUT × 1.024 × RA max. ÷ (RB min. // (R1 + R2) min.)
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
24
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 outp ut voltage remains immune to deviations
in the absolute accurac y of R A and RB and the absolute value of R1 an d R2 in the IC. In particular, to suppress the
influence of deviations in R1 and R2 i n the IC, a major contributor to deviations in the OUT , the RA and RB must be
limited to a much smaller value than th at of R1 and R2 in the IC.
On the other hand, a reactive current flows through RA and RB. This reactive current must be reduced to a
negligible value with res pect to the load current in the actual u se of the IC so that the efficiency characteristics will
not be degraded. T his requir es that the v alue of RA and R B be made suff icie ntly 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 o n actual e quipme nt.
There is a tradeoff between the voltage accuracy of the OUT and the reactive current. This should be taken into
consideration based o n the requ irem ents of the inte nded a pplicati on.
Deviations in the absolute value of the i nternal resistances (R1 and R2) in the IC vary with the output voltage of the
S-8520/8521 Series, and are broa dl y c lassifi ed as fo llows:
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 volta ge dev iati on will be obt ai ned f o r the OUT .
R1 + R2 = 2 ÷ (1 ÷ ma ximum deviation in ab solute 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 (R efer to Figure 14).
Make sure that CC is larger than the v alue g iven b y the foll o wing equation:
CC [F] ≥ 1 ÷ (2 × π × RA [Ω] × 7.5 kHz)
If a large CC value is selected, a longer s oft start time than t he one set u p in the IC will be set.
Caution The above connection diagram and constant will not guarantee successful operation. Perform
through evaluation using the actual application to set the constant.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 25
Characteristics (Typical Data)
1. Examples of major p a rameters 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
V
IN
[V]
I
SS1
[μA]
Ta =
−
40°C
Ta =
+
85°C
Ta =
+
25°C
(f
osc
= 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°C
Ta = +85°C
(2) Oscillation frequency (fosc)-Input voltag e (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°C
Ta =
+
25°C
Ta =
+
85°C
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
26
(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 CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 27
(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) ON/OFF
______
pin input voltage “H” (VSH)-
Input voltage (VIN) (8) ON/OFF
______
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 CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
28
(9) Output voltage (VOUT)-Input voltage (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 = 100 mA
IOUT = 500 mA
IOUT = 0.1 mA
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 = 100 mA
IOUT = 500 mA
IOUT = 0.1 mA
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 10 12 14 16
VIN [V]
VOUT [V]
IOUT = 0.1 mA
IOUT = 100 mA
IOUT = 500 mA
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
2 4 6 8 10 12 14 16
VIN [V]
VOUT [V]
IOUT = 100 mA
IOUT = 500 mA
IOUT = 0.1 mA
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 29
2. Transient Response Characteristics
2. 1 Power-on (IOUT: no load)
(1) S-8520/8521C3 0MC
(VIN = 0 V→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 V→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 V→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 V→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-8520/8521E3 3MC
(VIN = 0 V→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 V→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 CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
30
2. 2 Shutdown pin response (VON/OFF
______
= 0 V→1.8 V, IOUT = No load)
(1) S-8520/8521C3 0MC
(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-8520/8521E3 3MC
(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 CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 31
2. 3 Supply voltage variation (VIN = 4 V→9 V, 9 V→4 V)
(1) S-8520/8521C3 0MC (2) 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/di v
]
VIN
[2.5 V/div]
VOUT
[0.2 V/div]
0 V
10 V
(3) S-8520/8521A30MC (4) 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
(5) S-8520/8521E3 3MC (6) S-8520/8521E3 3MC
(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 CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
32
2. 4 Load variation
(1) S-8520/8521C3 0MC
(VIN = 3.6 V, IOUT = 0.1 mA→500 mA)
t [0.1 ms/div]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
(VIN = 3.6 V, IOUT = 500 mA→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 mA→500 mA)
t
[
0.1 ms/div
]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA (VIN = 3.6 V, IOUT = 500 mA→0.1 mA)
t
[
10 ms/div
]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA
(3) S-8520/8521E3 3MC
(VIN = 4.0 V, IOUT = 0.1 mA→500 mA)
t [0.1 ms/div]
IOUT
VOUT
[0.1 V/div]
0.1 mA
500 mA (VIN = 4.0 V, IOUT = 500 mA→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 CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 33
Reference Data
This reference data is intended to help you select peripheral components to be externally connected to the IC.
Therefore, this informat ion provides recommendations o n external components se lected with a view to accommodating
a wide variety of IC app lic ations. Char acter i stic data is dul y indicate d in t he table bel o w.
Table 11 External part s for efficien cy data
Product name Output voltage Induct or Transistor Diode Output capacitor Application
S-8520B30MC 3.0 V CD105 / 47 μH MA737 47 μF IOUT ≤ 1 A, VIN ≤ 10 V
S-8520F33MC D62F / 22 μH TM 6201 MA720 IOUT ≤ 0.5 A, VIN ≤ 10 V
S-8520F33MC 3.3 V CDH113 / 22 μH IRF7606 MA737 22 μF IOUT ≤ 1 A, VIN ≤ 16 V
S-8521D30MC TM6201
IOUT ≤ 0.5 A, VIN ≤ 10 V,
With equipment standby m od e
S-8521D30MC CD54 / 47 μH IRF7606 MA72 0 47 μF × 2 IOUT ≤ 0.5 A, VIN ≤ 16 V,
With equipment standby m od e
S-8521B30MC TM6201
IOUT ≤ 1 A, VIN ≤ 10 V,
With equipment standby m od e
S-8521B30MC
3.0 V
CD105 / 47 μH IRF7606 MA737 47 μF IOUT ≤ 1 A, VIN ≤ 16 V,
With equipment standby m od e
S-8521F33MC D62F / 22 μH TM6201 MA720 IOUT ≤ 0.5 A, VIN ≤ 10 V,
With equipment standby m od e
S-8521F33MC 3.3 V CDH113 / 22 μH IRF7606 MA737 22 μF IOUT ≤ 1 A, VIN ≤ 16 V,
With equipment standby m od e
S-8520B50MC CD54 / 47 μH TM6201 MA720 IOUT ≤ 0.5 A, VIN ≤ 10 V
S-8520B50MC CD105 / 47 μH IRF7606 MA737 47 μF IOUT ≤ 1 A, VIN ≤ 16 V
S-8520F50MC D62F / 22 μH TM6201 MA720 IOUT ≤ 0.5 A, VIN ≤ 10 V
S-8520F50MC CDH113 / 22 μH IRF7606 MA737 22 μF IOUT ≤ 1 A, VIN ≤ 16 V
S-8521D50MC CD54 / 47 μH TM6201 MA720 IOUT ≤ 0.5 A, VIN ≤ 10 V,
With equipment standby m od e
S-8521D50MC CD105 / 47 μH IRF7606 MA737 47 μF × 2 IOUT ≤ 1 A, VIN ≤ 16 V,
With equipment standby m od e
S-8521B50MC CD54 / 47 μH TM6201 MA720 IOUT ≤ 0.5 A, VIN ≤ 10 V,
With equipment standby m od e
S-8521B50MC CD105 / 47 μH IRF7606 MA737 47 μF IOUT ≤ 1 A, VIN ≤ 16 V,
With equipment standby m od e
S-8521F50MC D62F / 22 μH TM6201 MA720 IOUT ≤ 0.5 A, VIN ≤ 10 V,
With equipment standby m od e
S-8521F50MC
5.0 V
CDH113 / 22 μH IRF7606 MA737 22 μF IOUT ≤ 1 A, VIN ≤ 16 V,
With equipment standby m od e
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
34
Table 12 External p arts fo r Ripp le d ata
Product name Output voltage Inductor Transistor Rb C
b Diode Output capacitor
S-8520D30MC
S-8521D30MC 47 μF × 2
S-8520B30MC
S-8521B30MC
3.0 V CD105 / 47 μH 2SA1213 680 Ω 2200 pF MA720 22 μF × 2
S-8520F33MC − −
S-8521F33MC 3.3 V CDH11 3 / 22 μH IRF760 6 − − MA737 22 μF
S-8520D50MC
S-8521D50MC 47 μF × 2
S-8520B50MC
S-8521B50MC
CD105 / 47 μH 2SA1213 680 Ω 2200 pF MA720 22 μF × 2
S-8520F50MC − −
S-8521F50MC
5.0 V
CDH113 / 22 μH IRF7606 − − MA737 22 μF
Table 13 Performance Data
Component Product name Manufacturer name “L” value DC resistance Maximum
allowable
current Diameter Hei ght
CD54 0.37 Ω 0.72 A 5.8 mm 4.5 mm
CD105 47 μH 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
Inductor
D62F Toko Ink. 22 μH 0.25 Ω 0.70 A 6.0 mm 2.7 mm
MA720 Forward current 500 mA (at VF = 0.55 V)
Diode MA737 Matsushita Electric
Industrial Co., Ltd. Forward current 1.5 A (at VF = 0.5 V)
F93 Nichicon Corporation −
Output capacity TE Matsushita Electric
Industrial Co., Ltd. −
External transistor
(Bipolar PNP) 2SA1213 Toshiba Corporation
VCEO: 50 V max., IC: −2 A max., hFE: 120 to 240,
SOT-89-3 package
TM6201 Toyota Industries
Corporation
VGS: 12 V max., ID: −2 A max., V th: －0.7 V min.,
Ciss: 320 pF typ., Ron: 0.25 Ω max. (VGS = −4.5 V),
SOT-89-3 package
External transistor
(MOS FET) IRF7606 Internatio nal Rectifier
Corporation
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 package
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 35
1. Efficiency Characteristics: Output current (IOUT)-Efficiency (EFFI)
(1) S-8520B30MC
(CD105 / 47 μH, 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 μH, 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 μH, 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 μH, 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 μH, 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 μH, 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 μH, IR F7606)
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 CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
36
(5) S-8521F33MC
(D62F / 22 μH, 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 μH, 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 μH, 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 μH, 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 μH, 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 μH, 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 μH, 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 μH, 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 CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 37
(9) S-8521B50MC
(CD54 / 47 μH, 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 μH, 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 μH, 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 μH, 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 CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
38
2. Ripple Voltage Characteristics: Ripple voltage (V
rip
)-Input voltage (V
IN
) (L: CD105 / 47
μ
H, 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 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
(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
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
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.9.0_00 S-8520/8521 Series
Seiko Instruments Inc. 39
(9) S-8520B50MC (10) S-8521B5 0MC
(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 m A
(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 CONTROLLER
S-8520/8521 Series Rev.9.0_00
Seiko Instruments Inc.
40
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-8521D50MC
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-8521F 50MC
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
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• 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
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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 comm unity damage that may ensue.
