S-8540/8541 Series
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© Seiko Instruments Inc., 2000-2010
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM
SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0
_00
The S-8540/8541 Series is a family of CMOS step-down switching regulator controllers with PWM control (S-
8540 Series) and PWM/PFM switchover control (S-8541 Series). These devices consist of a reference voltage
source, oscillation circuit, an error amplifier, phase compensation circuit, PWM control circuit, current limit
circuit. A high efficiency and large current switching regulator is realized with the help of small external
components due to the high oscillation frequency, 300 kHz and 600 kHz.
The S-8540 Series provides low-ripple voltage, high efficiency, and excellent transient characteristics which
come from the PMW control circuit capable of varying the duty ratio linearly from 0 to 100%, the optimized error
amplifier, and the phase compensation circuit.
The S-8541 Series operates under PWM control when the duty ratio is 29% or higher and operates under PFM
control when the duty ratio is less than 29% to ensure high efficiency over all load range.
These controllers serve as ideal main power supply units for portable devices due to the high oscillation
frequencies together with the small 8-Pin MSOP package.
Features
•
Oscillation frequency
•
Output voltage
•
Output voltage precision
•
Feed back type for output voltage (FB)
•
External components:
•
Built-in PWM/PFM switchover control
circuit (S-8541 series)
•
Current limit circuit
•
Soft-start
•
Shutdown function
•
Lead-free, halogen-free
*1
*1.
Refer to “
600 kHz (A, B types)
300 kHz (C, D types)
1.5 to 6.0 V, selectable in 0.1V steps (A, C types)
±2.0%
a transistor, a coil, a diode, and capacitors
Duty ratio: 29% (PFM control)
29 to 100% (PWM control)
Current is set by an external resistor R
SENSE
.
Time is set by a capacitor C
SS
and a resistor R
SS
.
Product Name Structure”
for details.
Applications
•
Power supplies for PDAs, electric organizers, and portable devices.
•
Power supplies for audio equipment such as portable CD players and headphone stereos.
•
Main or sub Power supplies for notebook computers and peripheral equipment.
Package
•
8-Pin MSOP
Seiko Instruments Inc.
1
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0
_00
S-8540/8541 Series
Block Diagrams
1.
A, C types (fixed output voltage)
Pch Power
MOS FET
L
VIN
Power for IC
Triangular wave
oscillation circuit
PWM comparator
Phase
compensation
circuit
R
SENSE
SENSE
125 mV
VOUT
V
IN
EXT
SD
C
IN
Error amplifier
PWM or PWM / PFM
switching control
circuit
Shutdown soft start
circuit
C
OUT
V
REF
=1.0
V
Voltage/current
reference
VSS
ON/OFF
R
SS
C
SS
V
ON/OFF
CVREF
C
VL
Figure 1
2.
B, D types (feed back)
Pch Power
MOS FET
L
VIN
Power for IC
R
SENSE
SENSE
V
OUT
Triangular wave
oscillation circuit
PWM comparator
Phase
compensation
circuit
Error amplifier
125 mV
VOUT
C
FB
R
A
C
OUT
FB
V
REF
=1.0
V
Voltage/current
reference
V
IN
EXT
SD
C
IN
PWM or PWM / PFM
switching control
circuit
Shutdown soft start
circuit
R
B
VSS
ON/OFF
R
SS
C
SS
V
ON/OFF
CVREF
C
VL
Figure 2
2
Seiko Instruments Inc.
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0
_00
S-8540/8541 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, “2.
Package”
regarding the package drawings and “3.
Product name list”
for the full product names.
1.
Product name
S-854x x x FN - xxx T2 x
Environmental code
S: Lead-free, halogen-free
G: Lead-free (for details, please contact our sales office)
IC direction in tape specifications
*1
Product name (abbreviation)
*2
Package name (abbreviation)
FN: 8-Pin MSOP
Output voltage
*3
15 to 60
(e.g. When the output voltage is 1.5 V, it is expressed as 15.)
Product type
A: Fixed output voltage, fosc = 600 kHz
B: Feed back type, fosc = 600kHz
C: Fixed output voltage, fosc = 300 kHz
D: Feed back type, fosc = 300 kHz
Control system
0: PWM control
1: PWM/PFM switching control
*1.
*2.
*3.
Refer to the taping specifications at the end of this book.
Refer to the “3.
Product name list”.
00: Feed back type
2.
Package
Package Name
8-Pin MSOP
Drawing Code
Tape
FN008-A-C-SD
Package
FN008-A-P-SD
Reel
FN008-A-R-SD
Seiko Instruments Inc.
3
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0
_00
S-8540/8541 Series
3.
Product name list
3.1 A, B types (oscillation frequency: 600 kHz)
Output Voltage (V)
1.5
1.6
1.8
2.5
3.3
5.0
Feed back (1.5 to 6.0)
Table 1
S-8540xxxFN Series
S-8540A15FN-IAAT2z
−
S-8540A18FN-IADT2z
S-8540A25FN-IAKT2z
S-8540A33FN-IAST2z
S-8540A50FN-IBBT2z
S-8540B00FN-IMAT2z
S-8541xxxFN Series
−
S-8541A16FN-IGBT2z
S-8541A18FN-IGDT2z
S-8541A25FN-IGKT2z
S-8541A33FN-IGST2z
−
S-8541B00FN-IMDT2z
3.2 C,D types (oscillation frequency: 300 kHz)
Table 2
Output Voltage (V)
S-8540xxxFN Series
S-8541xxxFN Series
1.8
S-8540C18FN-ICDT2z
S-8541C18FN-IIDT2z
2.5
S-8540C25FN-ICKT2z
S-8541C25FN-IIKT2z
3.2
S-8541C32FN-IIRT2z
−
3.3
S-8540C33FN-ICST2z
S-8541C33FN-IIST2z
Feed back (1.5 to 6.0)
S-8540D00FN-IMBT2z
S-8541D00FN-IMET2z
Remark 1.
Please consult the SII marketing department for products with an output voltage other
than those specified above.
2.
z: G or S
3.
Please select products of environmental code = U for Sn 100%, halogen-free
products.
4
Seiko Instruments Inc.
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0
_00
S-8540/8541 Series
Pin Configuration
Table 3
Pin No. Pin Name
Pin Description
1
VSS
GND pin
2
EXT
Connection pin for external transistor
3
VIN
IC power supply pin
Bypass capacitor connection pin for
4
CVREF
reference voltage source
Shutdown pin
Soft-start capacitor connection pin
5
ON/
OFF
•
Normal operation (step-down operation)
•
All circuit halts (no step-down operation)
*1
None connected (A, C types)
NC
6
FB
Feed back pin (B, D types)
7
VOUT
Output voltage pin
8
SENSE
Current limit detection pin
*1.
The NC pin is electrically open.
The NC pin can be connected to VIN and VSS.
8-Pin MSOP
TOP view
1
2
3
4
8
7
6
5
Figure 3
Seiko Instruments Inc.
5
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