S-8521D50MC-BYJ-T2 [ETC]
Analog IC ; 模拟IC\n
| 型号： | S-8521D50MC-BYJ-T2 |
| 厂家： | 
ETC |
| 描述： | Analog IC
|
| 文件： | 总37页 (文件大小：596K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Rev.7.2
PWM Control & PWM/PFM Control
Step-Down Switching Regulator-Controllers
S-8520/8521 Series
The S-8520/8521 Series consists of CMOS step-down switching regulator-
controllers with PWM-control (S-8520) and PWM/PFM-switched control (S-
8521). These devices contain a reference voltage source, oscillation
circuit, error amplifier, and other components.
The S-8520 Series provides low-ripple power, high-efficiency, and
excellent transient characteristics thanks to a PWM control circuit capable
of varying the duty ratio linearly from 0% up to 100%. The series also
contains an error amplifier circuit as well as a soft-start circuit that prevents
overshoot at startup.
The S-8521 Series works with either PWM control or PFM control, and can
switch from one to the other. It normally operates using PWM control with
a duty ratio of 25% to 100%, but under a light load, it automatically
switches to PFM control with a duty ratio of 25%. This series ensures high
efficiency over a wide range of conditions, from standby mode to operation
of peripheral equipment.
With the addition of an external Pch Power MOS FET or PNP transistor, a coil,
capacitors, and a diode connected externally, these ICs can function as step-down
switching regulators. They serve as ideal power supply units for portable devices
when coupled with the SOT-23-5 minipackage, providing such outstanding
features as low current consumption. Since this series can accommodate an input
voltage of up to 16V, it is also ideal when operating via an AC adapter.
Features:
Applications:
•
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.
•
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:
•
•
•
•
•
•
•
•
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.
Selectable between 1.5 V and
6.0 V in steps of 0.1 V.
Duty ratio:
•
0% to 100% PWM control (S-8520)
25% to 100% PWM/PFM-switched control (S-8521)
The only peripheral components that can be used with this IC are a Pch power MOS FET or PNP
transistor, a coil, a diode, and capacitors (If a PNP transistor is used, a base resistance and a capacitor
will also be required).
•
•
Oscillation frequency: 180 kHz typ. (A & B Series), 60 kHz typ. (C & D Series), or 300 kHz typ. (E, F
Series).
Soft-start function: 8 msec. typ. (A & B Series) 12 msec. typ.(C & D Series), or 4.5 msec. typ. (E, F
Series).
•
•
With a power-off function.
With a built-in overload protection circuit. Overload detection time: 4 msec. typ. (A Series), 14 msec. typ.
(C Series) or 2.6 msec. typ.(E, F Series).
Seiko Instruments Inc.
1
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Block Diagram:
L
Tr
VOUT
Oscillation
Circuit
Reference Voltage
Source with Soft Start
VIN
PWM or
EXT
+
-
PWM/PFM-
Switched Control
Circuit
SD
VIN
Cout
Cin
VSS
ON / OFF
ON / OFF
Note: The diode inside the IC is a parasitic diode.
Figure 1 Block Diagram
Selection Guide:
1. Product Name
S - 852 X X XX MC - XXX - T2
Tape specifications.
Product name abbreviation.
Package name abbreviation.
Output voltage x 10
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.
Product type:
Control system 0: PWM control
1: PWM/PFM-switched control
2. Product List (As of July 31, 1998)
A & B Series (Oscillation Frequency of 180 kHz)
Item
S-8520AXXMC
Series
S-8521AXXMC
Series
S-8520BXXMC
Series
S-8521BXXMC
Series
Output Voltage (V)
2.5
3.0
3.3
5.0
S-8520A25MC-AVK-T2 S-8521A25MC-AXK-T2 S-8520B25MC-ARK-T2 S-8521B25MC-ATK-T2
S-8520A30MC-AVP-T2 S-8521A30MC-AXP-T2 S-8520B30MC-ARP-T2 S-8521B30MC-ATP-T2
S-8520A33MC-AVS-T2 S-8521A33MC-AXS-T2 S-8520B33MC-ARS-T2 S-8521B33MC-ATS-T2
S-8520A50MC-AWJ-T2 S-8521A50MC-AYJ-T2 S-8520B50MC-ASJ-T2 S-8521B50MC-AUJ-T2
2
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
C & D Series (Oscillation Frequency of 60 kHz)
Item
Output Voltage
S-8520CXXMC
Series
S-8521CXXMC
Series
S-8520DXXMC
Series
S-8521DXXMC
Series
(V)
2.5
3.0
3.3
5.0
S-8520C25MC-BRK-T2 S-8521C25MC-BTK-T2 S-8520D25MC-BVK-T2 S-8521D25MC-BXK-T2
S-8520C30MC-BRP-T2 S-8521C30MC-BTP-T2 S-8520D30MC-BVP-T2 S-8521D30MC-BXP-T2
S-8520C33MC-BRS-T2 S-8521C33MC-BTS-T2 S-8520D33MC-BVS-T2 S-8521D33MC-BXS-T2
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
S-8520EXXMC
Series
S-8521EXXMC
Series
S-8520FXXMC
Series
S-8521FXXMC
Series
(V)
3.0
3.3
5.0
S-8520E30MC-BJP-T2 S-8521E30MC-BLP-T2 S-8520F30MC-BNP-T2 S-8521F30MC-BPP-T2
S-8520E33MC-BJS-T2 S-8521E33MC-BLS-T2 S-8520F33MC-BNS-T2 S-8521F33MC-BPS-T2
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.
Pin Assignment:
SOT-23-5
Top view
Pin No. Pin Name
Function
Power-off pin
H: Normal operation (Step-down operation)
L: Step-down operation stopped (All circuits
deactivated)
1
5
4
ON/OFF
2
3
4
5
VSS
VOUT
EXT
VIN
GND pin
Output voltage monitoring pin
Connection pin for external transistor
IC power supply pin
1
2
Figure 2
3
Absolute Maximum Ratings:
Note: Although this IC incorporates an electrostatic protection circuit, the user is urged to avoid subjecting
it to an extremely high static electricity or static voltage in excess of the performance of the said
protection circuit.
(Ta = 25 oC unless otherwise specified)
Item
VIN pin voltage
Symbol
VIN *1
VOUT
ON/OFF *1
VEXT
Ratings
VSS -0.3 to VSS+12 or 18
VSS -0. 3 to VIN+0.3
VSS -0.3 to VSS+12 or 18
VSS -0.3 to VIN+0.3
±50
Unit
V
VOUT pin voltage
V
ON/OFF pin voltage
EXT pin voltage
V
V
EXT pin current
IEXT
mA
mW
oC
oC
Power dissipation
PD
150
Operating temperature range
Storage temperature range
TOPR
-40 to +85
TSTG
-40 to +125
*1: VSS+12 V for S-8520/21A/C/E; VSS+18 V for S-8520/21B/D/F
3
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Electrical Characteristics:
1. S-8520/21 A & B Series
(Ta = 25 °C, unless otherwise specified)
Parameter
Output voltage
Input voltage
Symbol
VOUT
VIN
Conditions
Min.
Typ.
Max.
Units
Measurement
Circuit
3
VOUT
X 0.976
2.5
VOUT
VOUT
X1.024
10.0
V
S-8520/21A Series
S-8520/21B Series
Vout = Output voltage x 1.2
Power-off pin = 0V
V
−
−
2
2.5
16.0
Current consumption 1
Current consumption during
power off
ISS1
ISSS
35
60
0.5
2
2
A
A
−
−
µ
µ
−
-2.3
-3.7
-4.5
-7.0
S-8520/21X15 24
−
−
−
−
−
−
−
−
−
−
−
S-8520/21X25 34
−
IEXTH VEXT = VIN-0.4V
-5.3
-9.3
S-8520/21X35 44
−
-6.7
-11.3
-13.3
+8.4
S-8520/21X45 54
−
EXT pin output current
-8.0
mA
S-8520/21X55 60
−
−
+4.3
+7.0
+9.9
+12.6
+15.0
S-8520/21X15 24
−
+13.2
+17.5
+21.4
+25.1
S-8520/21X25 34
−
IEXTL VEXT = 0.4V
S-8520/21X35 44
−
S-8520/21X45 54
−
S-8520/21X55 60
−
Line regulation
Load regulation
Vin = Output voltage x1.2 to x1.4 *3
Load current =10uA to IOUT(See below)
x1.25
30
30
60
60
mV
mV
3
3
VOUT1
VOUT2
∆
∆
−
−
Output voltage temperature
coefficient
3
3
VOUT Ta= - 40 C to 85 C
VOUT
x 5E-5
180
V/ C
∆
°
°
−
±
−
°
/ Ta
∆
Oscillation frequency
fosc
Measure waveform
at EXT pin
153
207
kHz
VOUT 2.5V
≥
144
15
180
25
216
40
VOUT 2.4V
≤
PWM/PFM-control switch PFM Duty Measure waveform at EXT pin under no
%
V
3
2
duty ratio
Power-Off pin
input voltage
Power-Off pin
input leakage current
Soft-Start time
*1
load.
VSH
VSL
ISH
ISL
Evaluate oscillation at EXT pin
Evaluate oscillation stop at EXT pin
1.8
−
−
−
4.0
2.0
−
−
−
−
8.0
4.0
−
0.3
0.1
-0.1
16.0
8.0
1
1
3
2
A
A
µ
µ
TSS
ms
ms
Overload detection time *2
TPRO Duration from the time Vout is reduced to
0V to the time the EXT pin obtains Vin.
EFFI
Efficiency
93
%
3
−
−
Conditions:
The recommended components are connected to the IC, unless otherwise indicated. Vin = Vout x 1.2 [V],
Iout = 120 [mA] (Vin = 2.5 V, if Vout ≤2.0 V.)
Peripheral components:
Coil
: Sumida Electric Co., Ltd. CD54 (47 µH).
: Matsushita Electronics Corporation MA720 (Schottky type).
: Matsushita Electronics Corporation TE (16 V, 22 µF tantalum type).
: Toshiba 2SA1213Y.
Diode
Capacitor
Transistor
Base resistance (Rb)
Base capacitor (Cb)
The power-off pin is connected to VIN.
: 0.68 kΩ
: 2200 pF (Ceramic type)
Notes:
The output voltage indicated above represents a typical output voltage set up. These specifications apply in
common to both S-8520 and S-8521, unless otherwise noted.
*1: Applicable to the S-8521A Series and S-8521B Series.
*2: Applicable to the S-8520A Series and S-8521A Series.
*3: Vin = 2.5 V to 2.94 V, if Vout ≤2.0 V.
4
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
2. S-8520/21 C & D Series
(Ta = 25 oC unless otherwise specified)
Parameter
Output voltage
Input voltage
Symbol
VOUT
VIN
Conditions
Min.
Typ.
Max.
Units
Measurement
Circuit
3
VOUT
X 0.976
2.5
VOUT
VOUT
X 1.024
10.0
V
S-8520/21C Series
S-8520/21D Series
V
−
−
2
2.5
16.0
Current consumption 1
Current consumption during
power-off
ISS1 Vout = Output voltage x 1.2
ISSS Power-off pin = 0V
10
21
0.5
2
2
A
A
−
−
µ
µ
−
-2.3
-3.7
-4.5
-7.0
S-8520/21X15 24
−
−
−
−
−
−
−
−
−
−
−
S-8520/21X25 34
−
IEXTH VEXT = VIN-0.4V
-5.3
-9.3
S-8520/21X35 44
−
-6.7
-11.3
-13.3
+8.4
S-8520/21X45 54
−
EXT pin output current
-8.0
mA
S-8520/21X55 60
−
−
+4.3
+7.0
+9.9
+12.6
+15.0
S-8520/21X15 24
−
+13.2
+17.5
+21.4
+25.1
S-8520/21X25 34
−
IEXTL VEXT = 0.4V
S-8520/21X35 44
−
S-8520/21X45 54
−
S-8520/21X55 60
−
Line regulation
Load regulation
Vin = Output voltage x1.2 to x1.4 *3
30
30
60
60
mV
mV
3
3
VOUT1
∆
∆
−
−
VOUT2 Load current =10 A to IOUT(See below)
µ
x1.25
Output voltage temperature
coefficient
3
3
VOUT
VOUT
x 5E-5
60
V/ C
∆
−
±
−
°
Ta = - 40 C to 85 C
°
°
/ Ta
∆
Oscillation frequency
fosc Measure waveform
at EXT pin
48
72
kHz
VOUT 2.5 V
≥
45
15
60
25
75
40
VOUT 2.4 V
≤
PWM/PFM-control switch PFM Duty Measure waveform at EXT pin under no
%
V
3
2
duty ratio *1
Power-Off pin
input voltage
load.
VSH Evaluate oscillation at EXT pin
VSL Evaluate oscillation stop at EXT pin
1.8
−
−
−
−
0.3
Power-Off pin
input leakage current
Soft-Start time
ISH
ISL
TSS
0.1
1
1
3
2
A
A
ms
ms
−
−
6.0
7.0
−
−
12.0
14.0
µ
µ
-0.1
24.0
28.0
Overload detection time *2
TPRO Duration from the time Vout is reduced to
0 V to the time the EXT pin obtains Vin.
EFFI
Efficiency
93
%
3
−
−
Conditions:
The recommended components are connected to the IC, unless otherwise indicated. Vin = Vout x 1.2 [V],
Iout = 120 [mA] (Vin = 2.5V, if Vout ≤2.0 V)
Peripheral components:
Coil
Diode
Capacitor
Transistor
: Sumida Electric Co., Ltd. CD54 (47 µH).
: Matsushita Electronics Corporation MA720 (Schottky type).
: Matsushita Electronics Corporation TE (16 V, 22 µF tantalum type).
: Toshiba 2SA1213Y.
Base resistance (Rb)
Base capacitor (Cb)
The power-off pin is connected to VIN.
: 0.68 kΩ
: 2200 pF (Ceramic type)
Notes:
The output voltage indicated above represents a typical output voltage set up. These specifications apply in
common to both S-8520 and S-8521, unless otherwise noted.
*1: Applicable to the S-8521C Series and S-8521D Series.
*2: Applicable to the S-8520C Series and S-8521C Series.
*3: Vin = 2.5 V to 2.94 V, if Vout ≤2.0 V.
5
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
3. S-8520/21 E & F Series
(Ta = 25 °C unless otherwise specified)
Parameter
Output voltage
Input voltage
Symbol
VOUT
VIN
Conditions
Min.
Typ.
Max.
Units
Measurement
Circuit
3
VOUT
X 0.976
2.5
VOUT
VOUT
X 1.024
10.0
V
S-8520/21E Series
S-8520/21F Series
VOUT =Output voltage x 1.2
Power-off pin = 0V
V
−
−
2
2.5
16.0
Current consumption 1
Current consumption during
power-off
ISS1
ISSS
60
100
0.5
2
2
A
A
−
−
µ
µ
−
-2.3
-3.7
-4.5
-7.0
S-8520/21X15 24
−
−
−
−
−
−
−
−
−
−
−
S-8520/21X25 34
−
IEXTH VEXT = VIN-0.4 V
-5.3
-9.3
S-8520/21X35 44
−
-6.7
-11.3
-13.3
+8.4
S-8520/21X45 54
−
EXT pin output current
-8.0
mA
S-8520/21X55 60
−
−
+4.3
+7.0
+9.9
+12.6
+15.0
S-8520/21X15 24
−
+13.2
+17.5
+21.4
+25.1
S-8520/21X25 34
−
IEXTL VEXT = 0.4 V
S-8520/21X35 44
−
S-8520/21X45 54
−
S-8520/21X55 60
−
Line regulation
Load regulation
Vin = Output voltage x1.2 to x1.4 *3
30
30
60
60
mV
mV
3
3
VOUT1
∆
∆
−
−
VOUT2 Load current =10 A to IOUT(See below)
µ
x1.25
Output voltage temperature
coefficient
3
3
VOUT
VOUT
x 5E-5
300
V/ C
∆
−
±
−
°
Ta = - 40 C to 85 C
°
°
/ Ta
∆
Oscillation frequency
fosc
Measure waveform
at EXT pin
240
360
kHz
VOUT 2.5V
≥
225
15
300
25
375
40
VOUT 2.4V
≤
PWM/PFM-control switch duty PFM Duty Measure waveform at EXT pin under no
%
V
3
2
ratio *1
Power-Off pin
input voltage
Power-Off pin
load.
VSH
VSL
ISH
ISL
Evaluate oscillation at EXT pin
Evaluate oscillation stop at EXT pin
1.8
−
−
−
2.0
1.3
−
−
−
−
4.5
2.6
−
0.3
0.1
-0.1
9.2
4.5
1
1
3
2
A
A
µ
µ
input leakage current
Soft-Start time
Overload detection time *2
TSS
ms
ms
TPRO Duration from the time Vout is reduced to
0 V to the time the EXT pin obtains Vin.
EFFI
Efficiency
90
%
3
−
−
Conditions:
The recommended components are connected to the IC, unless otherwise indicated. Vin = Vout x 1.2 [V],
Iout = 120 [mA] (Vin = 2.5 V, if Vout ≤2.0 V.)
Peripheral components:
Coil
Diode
Capacitor
Transistor
: Sumida Electric Co., Ltd. CD54 (47 µH).
: Matsushita Electronics Corporation MA720 (Schottky type).
: Matsushita Electronics Corporation TE (16 V, 22 µF tantalum type).
: Toshiba 2SA1213Y.
Base resistance (Rb)
Base capacitor (Cb)
The power-off pin is connected to VIN.
: 0.68KΩ
: 2200 pF (Ceramic type)
Notes:
The output voltage indicated above represents a typical output voltage set up. These specifications apply in
common to both S-8520 and S-8521, unless otherwise noted.
*1: Applicable to the S-8521E Series and S-8521F Series.
*2: Applicable to the S-8520E Series and S-8521E Series.
*3: Vin = 2.5 V to 2.94 V, if Vout ≤2.0 V.
6
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Measurement Circuits:
1
open
2
open
EXT
VOUT
VIN
A
VIN
EXT VOUT
VSS
+
-
ON/OFF
A
ON/OFF
VSS
3
0.68kΩ
2200pF
VIN
EXT
VOUT
+
-
+
-
V
ON/OFF
VSS
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.
7
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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 0.3V to 1.8V to the pin, lest the current consumption increase. When this power-off pin is not used,
leave it coupled to the VIN pin.
VIN
Power-Off Pin CR Oscillation Output
Circuit
Voltage
ON/OFF
“H”
“L”
Activated
Set
value
Deactivated
VSS
VSS
Figure 4
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 → 4.0V)
Power switched on
3V
Output voltage
(1V/div)
0V
1.5A
Rush current
(0.5A/div)
0A
t(1msec/div)
Figure 5 Waveforms of Output Voltage and Rush Current at Soft-Start
8
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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 soft-start in the IC, and the reference voltage will rise slowly from 0V. 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
Overload detection time
(TPRO)
Protection circuit ON
(TSS x 0.3)
Figure 6 Waveforms Appearing at EXT Pin As the Overload Protection Circuit Operates
9
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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 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.
10
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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
A
B
C
D
E
F
A
B
C
D
E
F
An overload protection
circuit is required
The input voltage range
exceeds 10V
The efficiency under light
loads(load current 1mA)
≤
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.
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) x (VIN - VOUT)
IPK = IOUT +
2 x fosc x L x (VIN + VF)
Where fosc is the oscillation frequency, L the inductance value of the coil, and VF the forward voltage
of the diode.
11
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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 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.
12
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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.
2SA1213-Y
VIN
Rb
Cb
EXT
VIN
Figure 7
The Rb-value is given by the following equation:
VIN-0.7
Ib
0.4
|IEXTL|
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:
1
Cb ≤
π
2 xRb x fOSC x 0.7
However, the practically-reasonable Cb value differs depending upon the characteristics of the bipolar
transistor. Optimize the Cb value based on the experiment result.
13
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Standard Circuits:
(1) Using a bipolar transistor:
L
Tr
VOUT
Oscillation
Circuit
Reference Voltage
Source with Soft-Start
VIN
Rb
Cb
PWM or
EXT
+
-
PWM/PFM-
Switched Control
Circuit
SD
VIN
Cout
Cin
ON / OFF
ON / OFF
VSS
Figure 8
(2) Using a Pch MOS-FET transistor
L
Tr
VOUT
Oscillation
Circuit
Reference Voltage
Source with Soft-Start
VIN
PWM or
EXT
+
-
PWM/PFM-
Switched Control
Circuit
SD
VIN
Cout
Cin
ON / OFF
ON / OFF
VSS
Figure 9
14
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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
PD
0
(mW)
0
50
100
150
Temperature Ta (0C)
Figure 10 Power dissipation of an SOT-23-5 Package (When Not Mounted)
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 (6V) 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.
OUT
CC
RA
RB
EXT
VOUT
S-8520/21 Series
VIN
PWM or
R1
R2
+
+
PWM/PFM-
Switched Control
Circuit
+
D1
--
−
Reference Voltage
Source with
Soft-Start
−
Oscillation
Cirucuit
ON/OFF
VSS
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.
15
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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.
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 1MΩ) 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 6.0V → 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.
16
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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
at:
SII Components Sales Dept.
Telephone: 043-211-1192 (Direct)
Fax: 043-211-8032
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.
at:
Telephone: 043-211-1192 (Direct)
Fax: 043-211-8032
17
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Characteristics of Major Items (All data represents typical values):
(1)
(2)
ISS1-VIN
ISS1-VIN
S-8520/21(Fosc:180kHz)
40
S-8520/21(Fosc:60kHz)
20
30
15
Ta=25
Ta=25
ISS1
(uA)
ISS1
(uA)
Ta=85
20
10
Ta=-40
Ta=85
10
0
5
0
Ta=-40
2
4
6
8
10
VIN(V)
12
14
16
2
4
6
8
10
12
14
16
VIN(V)
(3)
(4)
ISS1-VIN
Fosc-VIN
S-8520/21(Fosc:300kHz)
60
S-8520/21(Fosc:60kHz)
80
75
70
50
40
Ta=85
Ta=25
Ta=85
65
ISS1
30
Fosc
(kHz)
60
(uA)
Ta=25
Ta=-40
55
50
45
40
20
10
0
Ta=-40
2
4
6
8
10
VIN(V)
12
14
16
2
4
6
8
10
VIN(V)
12
14
16
(5)
(6)
Fosc-VIN
Fosc-VIN
S-8520/21(Fosc:180kHz)
220
S-8520/21(Fosc:300kHz)
360
210
200
340
320
190
Fosc
(kHz)
Fosc
300
Ta=25
180
(kHz)
Ta=25
170
160
150
140
280
260
240
Ta=-40
Ta=85
Ta=85
Ta=-40
2
4
6
8
10
12
14
16
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
18
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
(7)
(8)
IEXTL-VIN
S-8520/21
60
IEXTH-VIN
S-8520/21
-60
50
40
30
20
10
0
-50
Ta=-40
-40
-30
-20
-10
0
Ta=-40
Ta=25
Ta=25
Ta=85
IEXTL
(mA)
IEXTH
(mA)
Ta=85
2
4
6
8
10
12
14
16
16
16
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
(9)
(10)
TSS-VIN
TSS-VIN
S-8520/21(Fosc:180kHz)
25
S-8520/21(Fosc:60kHz)
25
Ta=-40
Ta=25
20
20
Ta=-40
Ta=25
15
15
TSS
TSS
(mS)
10
(mS)
10
Ta=85
5
0
5
0
Ta=85
2
4
6
8
10
12
14
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
(11)
(12)
TSS-VIN
TPRO-VIN
S-8520/21(Fosc:300kHz)
10
S-8520/21(Fosc:60kHz)
30
26
8
Ta=-40
Ta=85
22
6
Ta=-40
Ta=85
TSS
TPRO
(mS)
18
(mS)
4
14
10
6
Ta=25
Ta=25
2
0
2
4
6
8
10
12
14
16
2
4
6
8
10
12
14
VIN(V)
VIN(V)
19
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
(13)
(14)
TPRO-VIN
TPRO-VIN
S-8520/21(Fosc:180kHz)
8
S-8520/21(Fosc:300kHz)
4
Ta=85
7
6
Ta=85
3
Ta=-40
Ta=25
Ta=25
TPRO
5
TPRO
(mS)
(mS)
Ta=-40
4
3
2
2
1
2
4
6
8
10
12
14
16
2
4
6
8
10
VIN(V)
12
14
16
VIN(V)
(15)
(16)
VSL-VIN
S-8520/21
VSH-VIN
S-8520/21
1.8
1.7
1.5
1.3
1.1
0.9
0.7
0.5
0.3
1.6
1.4
1.2
1.0
0.8
0.6
0.4
Ta=-40
Ta=25
VSL
(V)
VSH
(V)
Ta=-40
Ta=25
Ta=85
Ta=85
2
4
6
8
10
12
14
16
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
(17)
VOUT-VIN
(18)
VOUT-VIN
S-8521B50MC (Ta=25°C)
S-8521B30MC (Ta=25°C)
5.08
5.07
5.06
5.05
3.08
3.07
3.06
3.05
Iout=0.1mA
Iout=500mA
Iout=0.1mA
Iout=500mA
5.04
VOUT
5.03
3.04
VOUT
3.03
(V)
(V)
5.02
3.02
Iout=100mA
5.01
5.00
4.99
4.98
3.01
3.00
2.99
Iout=100mA
14
2.98
2
4
6
8
10
12
16
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
20
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
(19)
(20)
VOUT-VIN
VOUT-VIN
S-8521F33MC (Ta=25°C)
S-8521F50MC (Ta=25°C)
3.38
3.37
3.36
3.35
5.07
5.06
5.05
5.04
Iout=0.1mA
Iout=100mA
Iout=0.1mA
Iout=100mA
3.34
VOUT
3.33
5.03
VOUT
5.02
(V)
(V)
3.32
5.01
3.31
3.30
3.29
3.28
5.00
4.99
4.98
4.97
Iout=500mA
14 16
Iout=500mA
14
2
4
6
8
10
12
16
2
4
6
8
10
12
VIN(V)
VIN(V)
21
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Transient Response Characteristics:
1. Power-On (Vin: 0V→3.6V or 4.0V, 0V→9.0V Iout: No-load)
S-8520/1C30MC (Vin:0→3.6V)
S-8520/1C30MC (Vin:0→9.0V)
10V
10V
Input
Voltage
(2.5V/div)
Input
Voltage
(2.5V/div)
0V
3V
0V
3V
Output
Voltage
(1V/div)
Output
Voltage
(1V/div)
0V
0V
t(2msec/div)
t(1msec/div)
t(1msec/div)
t(2msec/div)
t(1msec/div)
t(1msec/div)
S-8520/1A30MC (Vin:0→3.6V)
S-8520/1A30MC (Vin:0→9.0V)
10V
Input
Voltage
(2.5V/div)
10V
Input
Voltage
(2.5V/div)
0V
0V
3V
Output
Voltage
(1V/div)
3V
Output
Voltage
(1V/div)
0V
0V
S-8520/1E33MC (Vin:0→9.0V)
S-8520/1E33MC (Vin:0→4.0V)
10V
10V
Input
Voltage
(2.5V/div)
Input
Voltage
(2.5V/div)
0V
0V
3V
3V
Output
Voltage
(1V/div)
Output
Voltage
(1V/div)
0V
0V
22
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
2. Power-Off Terminal Response (ON/OFF: 0V→1.8V Iout : No-load)
S-8520/1C30MC (Vin:3.6V)
S-8520/1C30MC (Vin:9.0V)
3V
3V
Pow er of f
pin voltage
Pow er of f
pin voltage
0V
0V
3V
3V
Output
voltage
(1V/div)
Output
voltage
(1V/div)
0V
0V
t(2msec/div)
t(1msec/div)
t(1msec/div)
t(2msec/div)
t(1msec/div)
t(1msec/div)
S-8520/1A30MC (Vin:3.6V)
3V
S-8520/1A30MC (Vin:9.0V)
3V
Pow er of f
pin voltage
Pow er of f
pin voltage
0V
0V
3V
Output
voltage
(1V/div)
3V
Output
voltage
(1V/div)
0V
0V
S-8520/1E33MC (Vin:4.0V)
S-8520/1E33MC (Vin:9.0V)
3V
Pow er of f
pin voltage
3V
Pow er of f
pin voltage
0V
0V
3V
Output
voltage
(1V/div)
3V
Output
voltage
(1V/div)
0V
0V
23
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
3. Supply Voltage Variation (Vin: 4V→9V, 9V→4V)
S-8520/1C33MC (Iout:10mA)
S-8520/1C33MC (Iout:500mA)
10V
10V
Input
Input
Voltage
Voltage
³
(2.5V/div)
(2.5V/div)
0V
0V
Output
Output
Voltage
Voltage
³
(0.2V/div)
(0.2V/div)
t(0.5msec/div)
t(0.5msec/div)
t(0.5msec/div)
t(0.5msec/div)
t(0.5msec/div)
t(0.5msec/div)
S-8520/1A30MC
S-8520/1A30MC (Iout:500mA)
10V
Input
Voltage
10V
Input
Voltage
(2.5V/div)
(2.5V/div)
0V
0V
Output
Voltage
Output
Voltage
(0.2V/div)
(0.2V/div)
S-8520/1E33MC (Iout:10mA)
S-8520/1E33MC (Iout:500mA)
10V
Input
Voltage
(2.5V/div)
10V
Input
Voltage
(2.5V/div)
0V
0V
Output
Voltage
Output
Voltage
(0.2V/div)
(0.2V/div)
24
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
4. Load Variation (Vin: 3.6V or 4.0V Iout: 0.1mA→500mA, 500mA→0.1mA)
S-8520/1C30MC (Vin:3.6V)
S-8520/1C30MC (Vin:3.6V)
500mA
500mA
Output
Current
0.1mA
Output
Current
0.1mA
Output
Output
Voltage
(0.1V/div)
Voltage
(0.1V/div)
t(0.1msec/div)
t(5msec/div)
S-8520/1A30MC (Vin:3.6V)
500mA
S-8520/1A30MC (Vin:3.6V)
500mA
Output
Current
Output
Current
0.1mA
0.1mA
Output
Output
Voltage
(0.1V/div)
Voltage
(0.1V/div)
t(0.1msec/div)
t(10msec/div)
S-8520/1E33MC (Vin:4.0 V)
500mA
S-8520/1E33MC (Vin:4.0V)
500mA
Output
Output
Current
Current
0.1mA
0.1mA
Output
Voltage
Output
Voltage
(0.1V/div)
(0.1V/div)
t(0.1msec/div)
t(5msec/div)
25
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
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
Inductor
Transistor Diode Output
Application
Voltage
(V)
Capacitor
(µF)
(1) S-8520B30MC 3.0
(2) S-8520F33MC 3.3
TM6201 MA737
MA720
IRF7606 MA737
47
22
↑
CD105/47µH
D62F/22µH
CDH113/22µH
CD54/47µF
Iout≤1A, Vin ≤10V
Iout≤0.5A, Vin ≤10V
Iout≤1A, Vin ≤16V
↑
(3)
↑
↑
(4) S-8521D30MC 3.0
TM6201 MA720 47x2
Iout≤0.5A, Vin ≤10V
Equipment standby mode involved.
(5)
(6) S-8521B30MC
(7)
IRF7606
TM6201 MA737
IRF7606
↑
↑
↑
↑
↑
↑
↑
47
↑
Iout≤0.5A, Vin ≤16V
Equipment standby mode involved.
Iout≤1A, Vin ≤10V
Equipment standby mode involved.
CD105/47µF
↑
↑
↑
Iout≤1A, Vin ≤16V
Equipment standby mode involved.
(8) S-8521F33MC 3.3
(9)
(10) S-8520B50MC 5.0
TM6201 MA720
IRF7606 MA737
22
↑
D62F/22µH
CDH113/22µH
Iout≤0.5A, Vin≤ 10V
Equipment standby mode involved.
Iout≤1A, Vin ≤16V
Equipment standby mode involved.
Iout≤0.5A, Vin≤ 10V
Iout≤1A, Vin ≤16V
Iout≤0.5A, Vin ≤10V
Iout≤1A, Vin ≤16V
↑
↑
TM6201 MA720
IRF7606 MA737
TM6201 MA720
IRF7606 MA737
47
↑
22
↑
CD54/47µF
CD105/47µF
D62F/22µH
CDH113/22µH
CD54/47µF
(11)
(12) S-8520F50MC
(13)
(14) S-8521D50MC
↑
↑
↑
↑
↑
↑
TM6201 MA720 47x2
Iout≤0.5A, Vin ≤10V
Equipment standby mode involved.
(15)
(16) S-8521B50MC
(17)
(18) S-8521F50MC
(19)
IRF7606 MA737
↑
↑
↑
↑
↑
↑
CD105/47µF
CD54/47µF
↑
Iout≤1A, Vin ≤16V
Equipment standby mode involved.
Iout≤0.5A, Vin ≤10V
Equipment standby mode involved.
Iout≤1A, Vin ≤16V
Equipment standby mode involved.
Iout≤0.5A, Vin ≤10V
Equipment standby mode involved.
TM6201 MA720
IRF7606 MA737
TM6201 MA720
IRF7606 MA737
47
↑
↑
CD105/47µF
D62F/22µH
22
↑
↑
CDH113/22µH
Iout≤1A, Vin ≤16V
Equipment standby mode involved.
26
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
Table 2 Ripple Data
No.
Product Name
Output
Voltage
(V)
Inductor
(µH)
Transistor
Rb
(Ω)
Cb
(pF)
Diode
Output
Capacitor
(µF)
(20)
(21)
(22)
(23)
(24)
(25)
(26)
(27)
(28)
(29)
(30)
(31)
S-8520D30MC
S-8521D30MC
S-8520B30MC
S-8521B30MC
S-8520F33MC
S-8521F33MC
S-8520D50MC
S-8521D50MC
S-8520B50MC
S-8521B50MC
S-8520F50MC
S-8521F50MC
3.0
↑
↑
↑
3.3
↑
CD105/47 2SA1213Y 680
2200
↑
↑
↑
−
−
2200
↑
↑
↑
−
−
MA720
47x2
↑
22 x2
↑
22
↑
47 x2
↑
22 x2
↑
22
↑
↑
↑
↑
↑
↑
↑
↑
↑
↑
−
−
↑
↑
↑
CDH113/22 IRF7606
MA737
↑
↑
↑
5.0
↑
↑
↑
↑
CD105/47 2SA1213Y 680
MA720
↑
↑
↑
↑
↑
↑
↑
↑
↑
−
−
↑
↑
↑
MA737
↑
CDH113/22 IRF7606
↑
↑
↑
Table 3 Performance Data
Product Manufacturer's L-Value DC
Component
Max.
Dia.
(mm)
Height
(mm)
Name Name
(µH) Resistance Allowable
Current
(A)
(Ω)
Inductor
CD54 Sumida Electric
Co., Ltd
47
0.37
0.72
5.8
4.5
↑
↑
↑
22
↑
CD105
CDH113
D62F
0.17
0.09
0.25
1.28
1.44
0.70
10.0
11.0
6.0
5.4
3.7
2.7
Toko
Diode
MA720
Matsushita
Electronics
Corporation
↑
Forward current 500mA (When VF = 0.55V)
MA737
F93
Forward current 1.5A (When VF = 0.5V)
Output Capacity
Nichicon
TE
Matsushita
Electronics
Corporation
Toshiba
External Transistor 2SA1213Y
(Bipolar PNP)
VCEO 50V max. , Ic-2A max., hFE 120 to 240
SOT-89-3 PKG
Corporation
External Transistor TM6201 Toyota Automatic VGS 12V max. , ID -2A max. , Vth -0.7V min. , Ciss 320pF typ.
(MOS FET) Loom Works, Ltd.
Ron 0.25Ω max.(Vgs=-4.5V), SOT-89-3 PKG
International VGS 20V max. , ID -2.4A max. , Vth -1V min. Ciss 470pF typ.
Rectifier
IRF7606
Ron 0.15Ω max.(Vgs=-4.5V), Micro 8 PKG
27
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
1. Efficiency Characteristics
(1)
S-8520B30MC
Output current - Efficiency (CD105/47uH,TM6201)
100
90
80
Efficiency
(%)
70
60
Vin=3.6V
Vin=9.0V
50
0.01
0.1
1
10
100
1000
Output current (mA)
(2)
(3)
S-8520F33MC
S-8520F33MC
Output current - Efficiency (CDH113/22uH,IRF7606)
100
Output current - efficiency (D62F/22uH,TM6201)
100
Vin=14V
Vin=9V
90
90
Vin=9V
Vin=6V
Vin=6V
80
Vin=4V
80
Vin=4V
Efficiency
(%)
Efficiency
(%)
70
60
50
70
60
50
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
(4)
(5)
S-8521D30MC
S-8521D30MC
Output current - Efficiency (CD54/47uH,TM6201)
100
Output current - Efficiency (CD54/47uH,IRF7606)
100
90
80
70
60
50
90
80
Efficiency
(%)
Efficiency
(%)
70
60
50
Vin=3.6V
Vin=9.0V
Vin=3.6V
Vin=9.0V
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output curent (mA)
28
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
(6)
(7)
S-8521B30MC
S-8521B30MC
Output current - Efficiency (CD105/47uH,TM6201)
100
Output current - Efficiency (CD105/47uH,IFR7606)
100
90
80
70
60
50
90
80
Efficiency
(%)
Efficiency
(%)
70
60
50
Vin=3.6V
Vin=9.0V
Vin=3.6V
Vin=9.0V
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
(8)
(9)
S-8521F33MC
S-8521F33MC
Output current - Efficiency (D62F/22uH,TM6201)
100
Output current - Efficiency (CDH113/22uH,IRF7606)
100
Vin=14V
Vin=9V
90
90
Vin=9V
Vin=6V
Vin=6V
80
Vin=4V
80
Efficiency
(%)
Efficiency
(%)
Vin=4V
70
60
50
70
60
50
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
(10)
(11)
S-8520B50MC
S-8520B50MC
Output current - Efficiency (CD54/47uH,TM6201)
100
Output current - Efficiency (CD105/47uH,IRF7606)
100
Vin=14V
90
80
90
Vin=9V
Vin=6V
80
Efficiency
(%)
Efficiency
(%)
70
60
50
70
60
50
Vin=6.0V
Vin=9.0V
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
29
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
(12)
(13)
S-8520F50MC
S-8520F50MC
Output current - Efficiency (CDH113/22uH,IRF7606)
100
Output current - Efficiency (D62F/22uH,TM6201)
100
Vin=14V
Vin=9V
90
90
Vin=9V
Vin=6V
Vin=6V
80
80
Efficiency
(%)
Efficiency
(%)
70
60
50
70
60
50
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
(14)
(15)
S-8521D50MC
S-8521D50MC
Output current - Efficiency (CD54/47uH,TM6201)
100
Output current - Efficiency (CD105/47uH,IRF7606)
100
90
80
90
80
Efficiency
(%)
Efficiency
(%)
70
60
50
70
60
50
Vin=14V
Vin=6.0V
Vin=9.0V
Vin=9V
Vin=6V
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
(16)
(17)
S-8521B50MC
S-8521B50MC
Output current - Efficiency (CD105/47uH,IRF7606)
100
Output current - Efficiency (CD54/47uH,TM6201)
100
Vin=14V
90
90
80
Vin=9V
Vin=6V
80
Efficiency
(%)
Efficiency
(%)
70
60
50
70
60
50
Vin=6.0V
Vin=9.0V
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
30
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
(18)
(19)
S-8521F50MC
S-8521F50MC
Output current - Efficiency (D62F/22uH,TM6201)
100
Output current - Efficiency (CDH113/22uH,IRF7606)
100
Vin=9V
Vin=14V
90
90
Vin=6V
Vin=9V
Vin=6V
80
80
70
60
50
Efficiency
(%)
Efficiency
(%)
70
60
50
0.01
0.1
1
10
100
1000
0.01
0.1
1
10
100
1000
Output current (mA)
Output current (mA)
31
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
2. Ripple Voltage Characteristics(L:CD105/47uF, Tr:2SA1213, SBD:MA720)
(20)
(21)
Ripple voltage-VIN
S-8520D30MC(Cout:47uFx2)
240
Ripple voltage-VIN
S-8521D30MC(Cout:47uFx2)
240
200
160
200
160
Iout=500mA
Iout=500mA
Iout=100mA
Iout=100mA
Iout=0.1mA
Vr
120
Vr
120
Iout=0.1mA
(mV)
(mV)
80
40
0
80
40
0
2
4
6
8
10
12
14
16
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
(22)
(23)
Ripple voltage-VIN
Ripple voltage-VIN
S-8520B30MC(Cout:22uFx2)
240
S-8521B30MC(Cout:22uFx2)
240
200
160
200
160
Iout=500mA
Iout=100mA
Iout=0.1mA
Iout=500mA
Iout=100mA
Vr
120
Vr
120
(mV)
(mV)
80
40
0
80
40
0
Iout=0.1mA
2
4
6
8
10
12
14
16
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
(24)
(25)
Ripple voltage-VIN
Ripple voltage-VIN
S-8520F33MC(Cout:22uF)
240
S-8521F33MC(Cout:22uF)
240
200
160
200
160
Iout=500mA
Iout=100mA
Iout=500mA
Iout=100mA
Iout=0.1mA
Iout=0.1mA
Vr
120
Vr
120
(mV)
(mV)
80
40
0
80
40
0
2
4
6
8
10
12
14
16
2
4
6
8
10
12
14
16
VIN(V)
VIN(V)
32
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
(26)
(27)
Ripple voltage-VIN
S-8520D50MC(Cout:47uFx2)
240
Ripple voltage-VIN
S-8521D50MC(Cout:47uFx2)
240
200
200
Iout=500mA
Iout=500mA
Iout=100mA
Iout=0.1mA
160
120
80
40
0
160
120
80
40
0
Iout=100mA
Iout=0.1mA
Vr
(mV)
Vr
(mV)
2
4
6
8
10
10
10
12
12
12
14
14
14
16
16
16
2
4
6
8
10
10
10
12
12
12
14
14
14
16
16
16
VIN(V)
VIN(V)
(28)
(29)
Ripple voltage-VIN
S-8521B50MC(Cout:22uFx2)
240
Ripple voltage-VIN
S-8520B50MC(Cout:22uFx2)
240
200
160
200
Iout=500m
160
120
80
40
0
Iout=100m
Iout=0.1mA
Iout=500mA
Vr
(mV)
Vr
(mV)
120
80
40
0
Iout=100mA
Iout=0.1mA
2
4
6
8
2
4
6
8
VIN(V)
VIN(V)
(30)
(31)
Ripple voltage-VIN
S-8520F50MC(Cout:22uF)
240
Ripple voltage-VIN
S-8521F50MC(Cout:22uF)
240
200
160
200
160
Iout=500mA
Iout=500mA
Iout=100mA
Iout=100mA
Iout=0.1mA
Iout=0.1mA
Vr
120
Vr
120
(mV)
(mV)
80
40
0
80
40
0
2
4
6
8
2
4
6
8
VIN(V)
VIN(V)
33
Seiko Instruments Inc.
PWM Control & PWM/PFM Control Step-Down Switching Regulator-Controllers
S-8520/8521 Series
Rev.7.2
3. PWM/PFM
(5)
(7)
S-8521D30MC
S-8521B30MC
PWM/PFM switching characteristics
PWM/PFM switching characteristics
14
14
10
Input
10
Input
voltage
voltage
(V)
6
(V)
6
2
2
1
10
100
1000
1
10
100
1000
Output current (mA)
Output current (mA)
(9)
(15)
S-8521D50MC
S-8521F33MC
PWM/PFM switching characteristics
PWM/PFM switching characteristics
14
14
10
Input
10
Input
voltage
voltage
(V)
6
(V)
6
2
2
1
10
100
1000
1
10
100
1000
Output current (mA)
Output current (mA)
(17)
(19)
S-8521B50MC
PWM/PFM switching characteristics
S-8521F50MC
PWM/PFM switching characteristics
14
14
10
Input
voltage
(V)
6
10
Input
voltage
(V)
6
2
2
1
10
100
1000
1
10
100
1000
Output current (mA)
Output current (mA)
34
Seiko Instruments Inc.
MP005-A 991105
SOT-23-5
Unit mm
Dimensions
2.9±0.2
1.9±0.2
0.45
5
4
+0.2
-0.3
2.8
1.6
0.16 +0.1
-0.06
3
1
2
1.1±0.1
1.3max
0.95 0.1
0.4±0.1
Taping Specifications
Reel Specifications
4.0±0.1 (10 pitches 40.0±0.2)
3000 pcs./reel
2.0±0.05
ø1.5 +0.1
-0
0.27±0.05
12.5max.
3
max.
+0.1
-0
ø1.0
4.0±0.1
3
max.
1.4±0.2
3.25±0.15
9.0±0.3
21±0.5
φ13±0.2
2±0.2
(60°)
(60°)
Feed direction
809/816/8520
990603
Markings
SOT-23-5
4
5
1
3
·
·
The information herein is subject to change without notice.
Seiko Instruments Inc. is not responsible for any problems caused by circuits or other diagrams
described herein whose industrial properties, patents or other rights belong to third parties. The
application circuit examples explain typical applications of the products, and do not guarantee any
mass-production design.
·
·
When the products described herein include Strategic Products (or Service) subject to regulations,
they should not be exported without authorization from the appropriate governmental authorities.
The products described herein cannot be used as part of any device or equipment which influences
the human body, such as physical exercise equipment, medical equipment, security system, gas
equipment, vehicle or airplane, without prior written permission of Seiko Instruments Inc.
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