PWM CONTROL & PWM/PFM CONTROL STEP-DOWN
SWITCHING REGULATOR-CONTROLLERS
The S-8520/8521 Series consists of CMOS step-down switching
regulator-controllers with PWM-control (S-8520) and PWM/PFM-
switched control (S-8521).
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 equip-
ment.
They serve as ideal power supply units for portable devices when
coupled with the SOT-23-5 minipackage, providing such outstand-
ing features as low current consumption.
Moreover, oscillation frequency, a 300kHz type (E, F Series) is
also available.
NEW S-8520/8521 Series
FEATURES
• Low current consumption:
In operation
: 60
µA
max. (A & B Series)
21
µA
max. (C & D Series)
100µA max. (E & F Series)
When powered off
: 0.5
µA
max.
• Input voltage
: 2.5V to 16V (B & D & F Series)
2.5V to 10V (A & C & E Series)
• Output voltage : Selectable between 1.5V and 6.0V in steps of 0.1V.
• 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 type. (A & B Series), 60 kHz type.
(C & D Series), or 300 kHz type. (E & F Series).
• Soft-start function: 8 msec type. (A & B Series) or 12 msec type
(C & D Series) or 4.5 msec type (E & F Series).
• With power-off function.
• With a built-in overload protection circuit. Overload detection
time: 4 msec type. (A Series) or 14 msec type. (C Series) or 2.6
msec type (E & F Series).
PIN CONFIGURATIONS
SOT-23-5
Top view
5
4
Pin No.
1
1
2
3
2
3
4
5
Pin Name
Function
ON/OFF Power-off terminal
"H" : Normal operation (Step-down operation)
"L" : Step-down operation stopped
(All circuit deactivated)
V
SS
GND pin
V
OUT
Output voltage monitering terminal
EXT
Connection terminal for external transistor
V
IN
IC power supply terminal
APPLICATIONS
• On-board power supplies of battery devices for portable tele-
phones, electronic notebooks, PCAs, and the like.
• Power supplies for audio equipment, including portable CD play-
ers 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 3.3V/3V.
• Conversion of AC adapter input to 5V/3V.
S-8520BXXMC Series
S-8520B25MC-ARK-T2
S-8520B30MC-ARP-T2
S-8520B33MC-ARS-T2
S-8520B50MC-ASJ-T2
S-8521BXXMC Series
S-8521B25MC-ATK-T2
S-8521B30MC-ATP-T2
S-8521B33MC-ATS-T2
S-8521B50MC-AUJ-T2
PRODUCT LIST
A, B Series (Oscillation frequency 180kHz)
Item
Output Voltage (V)
2.5
3.0
3.3
5.0
S-8520AXXMC Series
S-8520A25MC-AVK-T2
S-8520A30MC-AVP-T2
S-8520A33MC-AVS-T2
S-8520A50MC-AWJ-T2
S-8521AXXMC Series
S-8521A25MC-AXK-T2
S-8521A30MC-AXP-T2
S-8521A33MC-AXS-T2
S-8521A50MC-AYJ-T2
C, D Series (Oscillation frequency 60kHz)
Item
Output Voltage (V)
2.5
3.0
3.3
5.0
S-8520CXXMC Series
S-8520C25MC-BRK-T2
S-8520C30MC-BRP-T2
S-8520C33MC-BRS-T2
S-8520C50MC-BSJ-T2
S-8521CXXMC Series
S-8521C25MC-BTK-T2
S-8521C30MC-BTP-T2
S-8521C33MC-BTS-T2
S-8521C50MC-BUJ-T2
S-8520DXXMC Series
S-8520D25MC-BVK-T2
S-8520D30MC-BVP-T2
S-8520D33MC-BVS-T2
S-8520D50MC-BWJ-T2
S-8521DXXMC Series
S-8521D25MC-BXK-T2
S-8521D30MC-BXP-T2
S-8521D33MC-BXS-T2
S-8521D50MC-BYJ-T2
E, F Series (Oscillation frequency 300kHz)
Item
Output Voltage (V)
3.0
3.3
5.0
S-8520EXXMC Series
S-8520E30MC-BJP-T2
S-8520E33MC-BJS-T2
S-8520E50MC-BKJ-T2
S-8521EXXMC Series
S-8521E30MC-BLP-T2
S-8521E33MC-BLS-T2
S-8521E50MC-BMJ-T2
S-8520FXXMC Series
S-8520F30MC-BNP-T2
S-8520F33MC-BNS-T2
S-8520F50MC-BOJ-T2
S-8521FXXMC Series
S-8521F30MC-BPP-T2
S-8521F33MC-BPS-T2
S-8521F50MC-BQJ-T2
Some products described here in are under development.
Please contact us for Samples.
BLOCK DIAGRAM
L
VOUT
VIN
Oscillation Circuit
Reference voltage
source with soft start
+
Tr
EXT
VIN
+
Cin
SD
PWM or PWM/PFM-
switched control circuit
+
-
Cout
ON/OFF
ON/OFF
Note : The diode inside the IC is a parasitic diode
VSS
17
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