Rev.3.2
_00
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE
SWITCHING REGULATOR CONTROLLER
S-8540/8541 Series
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
•
Small package
•
Lead-free products
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
.
8-Pin MSOP
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
Package Name
8-Pin MSOP
Package
FN008-A
Drawing Code
Tape
FN008-A
Reel
FN008-A
Seiko Instruments Inc.
1
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.3.2
_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 and “2.
Product Name List”
for the full product names.
1.
Product name
S-854X X XX FN - XXX T2 G
IC direction in tape specifications
Product code
*2
Package code
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
*1.
*2.
*3.
Refer to the taping specifications at the end of this book.
Refer to the “2.
Product name list”.
00: Feed back type
Seiko Instruments Inc.
3
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.3.2
_00
S-8540/8541 Series
2.
Product name list
2.1 A, B types (oscillation frequency: 600 kHz)
Output Voltage (V)
Table 1
S-8540XXXFN Series
S-8541XXXFN Series
1.5
S-8540A15FN-IAAT2G
−
1.6
S-8541A16FN-IGBT2G
−
1.8
S-8540A18FN-IADT2G
S-8541A18FN-IGDT2G
2.5
S-8540A25FN-IAKT2G
S-8541A25FN-IGKT2G
3.3
S-8540A33FN-IAST2G
S-8541A33FN-IGST2G
5.0
S-8540A50FN-IBBT2G
−
Feed back (1.5 to 6.0)
S-8540B00FN-IMAT2G
S-8541B00FN-IMDT2G
Remark
Please consult the SII marketing department for products with an output voltage
other than those specified above.
2.2 C,D types (oscillation frequency: 300 kHz)
Table 2
Output Voltage (V)
S-8540XXXFN Series
S-8541XXXFN Series
1.8
S-8540C18FN-ICDT2G
S-8541C18FN-IIDT2G
2.5
S-8540C25FN-ICKT2G
S-8541C25FN-IIKT2G
3.2
S-8541C32FN-IIRT2G
−
3.3
S-8540C33FN-ICST2G
S-8541C33FN-IIST2G
Feed back (1.5 to 6.0)
S-8540D00FN-IMBT2G
S-8541D00FN-IMET2G
Remark
Please consult the SII marketing department for products with an output voltage
other than those specified above.
4
Seiko Instruments Inc.
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.3.2
_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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