Rev.7.5
_00
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE
SWITCHING REGULATOR CONTROLLER
S-8520 / 8521 Series
The S-8520 / 8521 Series consists of CMOS step-down
switching regulator-controllers with PWM control (S-8520
Series) and PWM / PFM switching control (S-8521
Series). These devices contain a reference voltage
source, oscillation circuit, error amplifier, and other
components.
The S-8520 Series provides low-ripple power, high-
efficiency, and excellent transient characteristics thanks to
a PWM control circuit capable of varying the duty ratio
linearly from 0% up to 100%. The series also contains
an error amplifier circuit as well as a soft-start circuit that
prevents overshoot at startup.
The S-8521 Series works with either PWM control or PFM
control, and can switch from one to the other. It normally
operates using PWM control with a duty ratio of 25 to
100%, but under a light load, it automatically switches to
PFM control with a duty ratio of 25%. This series
ensures high efficiency over a wide range of conditions,
from standby mode to operation of peripheral equipment.
With the addition of an external Pch power MOS FET or
PNP transistor, a coil, capacitors, and a diode connected
externally, these ICs can function as step-down switching
regulators. They serve as ideal power supply units for
portable devices when coupled with the SOT-23-5 small
package, providing such outstanding features as low
current consumption.
Since this series can
accommodate an input voltage of up to 16 V, it is also
ideal when operating via an AC adapter.
Features
•
Low current consumption
During operation: 60
µA
max. (A, B types)
21
µA
max. (C, D types)
100
µA
max. (E, F types)
During shutdown: 0.5
µA
max.
•
Input voltage:
2.5 to 16 V (B, D, F types)
2.5 to 10 V (A, C, E types)
•
Output voltage:
Selectable between 1.5 V and 6.0 V in 0.1 V step
•
Duty ratio:
0 to 100% PWM control (S-8520 Series)
25 to100% PWM / PFM switching control (S-8521 Series)
•
The only peripheral components that can be used with this IC are a Pch power MOS FET or PNP
transistor, a coil, a diode, and capacitors (If a PNP transistor is used, a base resistance and a capacitor will
also be required).
•
Oscillation frequency:
180 kHz typ.
(A, B types)
60 kHz typ.
(C, D types)
300 kHz typ.
(E, F types)
•
Soft-start function:
8 ms. typ.
(A, B types)
12 ms. typ.
(C, D types)
4.5 ms. typ.
(E, F types)
•
With a shutdown function
•
With a built-in overload protection circuit
Overload detection time: 4 ms. typ. (A type)
14 ms. typ. (C type)
2.6 ms. typ. (E type)
Seiko Instruments Inc.
1
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5
_00
S-8520 / 8521 Series
Applications
•
On-board power supplies of battery devices for portable telephones, electronic notebooks, PDAs.
•
Power supplies for audio equipment, including portable CD players and headphone stereo equipment.
•
Fixed voltage power supply for cameras, video equipment and communications equipment.
•
Power supplies for microcomputers.
•
Conversion from four NiH or NiCd cells or two lithium-ion cells to 3.3 V / 3 V.
•
Conversion of AC adapter input to 5 V / 3 V.
Package
Package Name
SOT-23-5
Package
MP005-A
Drawing code
Tape
MP005-A
Reel
MP005-A
2
Seiko Instruments Inc.
STEP-DOWN, PWM CONTROL or PWM / PFM SWITCHABLE SWITCHING REGULATOR CONTROLLOR
Rev.7.5
_00
S-8520 / 8521 Series
Product Name Structure
•
The control types, product types, and output voltage for the S-8540 / 8541 series can be selected at the
user’s request. Please refer to the “1.
Product name”
for the definition of the product name and “2.
Product Name List”
for the full product names.
1. Product name
S-852 x x xx MC - xxx - T2
IC direction in tape specifications
*1
Product code
*2
Package code
MC: SOT-23-5
Output voltage
15 to 60
(Ex. When the output voltage is 1.5 V, it is expressed as 15.)
Product type
A: Oscillation frequency of 180 kHz,
With overload protection circuit.
B: Oscillation frequency of 180 kHz,
Without overload protection circuit.
C: Oscillation frequency of 60 kHz,
With overload protection circuit.
D: Oscillation frequency of 60 kHz,
Without overload protection circuit.
E: Oscillation frequency of 300 kHz,
With overload protection circuit.
F: Oscillation frequency of 300 kHz,
Without overload protection circuit.
Control system
0: PWM control
1: PWM/PFM switching control
Refer to the taping specifications at the end of this book.
Refer to “2.
Product name list”.
*1.
*2.
4
Seiko Instruments Inc.
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