Rev.1.1
_70
PWM Control & PWM/PFM Control High-Frequency
Step-Down Switching Regulator Controllers
S-8540/8541 Series
The S-8540/8541 Series is a family of CMOS step-down switching
regulator controllers with PWM control (S-8540) and PWM/PFM switchover
control (S-8541). 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 provides low-ripple voltage, high efficiency, and excellent
transient characteristics which come form 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 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:
•
•
•
•
•
•
•
600 kHz (A & B series), 300 kHz (C & D series)
1.5 V to 6.0 V in steps of 0.1 V (A & C series)
Variable (Feed back) type is available.
Output voltage precision:
±2.0 %
External components:
A transistor, a coil, a diode, and capacitors.
Built-in PWM/PFM switchover control circuit(S-8541)
Duty ratio:
29
%
(PFM control)
29 to 100
%
(PWM control)
Current limit circuit:
Current is set by an external resistor R
SENSE
.
Soft-start:
Time is set by an capacitor C
SS
and a resistor R
SS
.
Power-off function
Small package:
8-Pin MSOP
Package
•
8-Pin MSOP (Package drawing code: FN008-A)
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.
Seiko Instruments Inc.
1
PWM Control & PWM/PFM Control High-Frequency Step-Down Switching Regulator-Controllers
S-8540/8541 Series
Rev.1.1
_70
Block Diagram
Pch Power
MOS FET
L
VIN
Power for IC
Triangular wave
oscillation circuit
PWM comparator
Phase
compensation
circuit
Error amplifier
R
SENSE
SENSE
SENSE
R
SENSE
V
OUT
125mV
VOUT
125mV
V
IN
EXT
VOUT
C
FB
R
A
C
OUT
R
B
C
OUT
SD
C
IN
FB
PWM or
PWM/PFM
switching control
Power-off soft start
circuit
V
REF
=
1.0V
Voltage/current
reference
VSS
VSS
ON/OFF
R
SS
CSS
V
ON/OFF
CVREF
C
VL
Figure 1 Block diagram
Selection Guide
1. Product Name
S-854X X XX FN - XXX - T2
Tape specifications.
Product name abbreviation.
Package name abbreviation (8-Pin MSOP).
Output voltage (1.5 to 6.0 V), 00: Feed back type
A: Fixed output voltage, fosc=600 kHz
B: Feed back type, fosc=600kHz
C: Fixed output voltage, fosc=300 kHz
D: Feed back0type, fosc=300 kHz
0: PWM control
1: PWM/PFM switchover control
2. Product List (as of November 1, 2000)
2-1 A, B Series (oscillation frequency: 600 kHz)
Output Voltage (V)
1.8 V
2.5 V
3.3 V
Feed back (1.5 to 6.0)
S-8540XXXFN Series
S-8540A18FN-IAD-T2
S-8540A25FN-IAK-T2
S-8540A33FN-IAS-T2
S-8540B00FN-IMA-T2
S-8541XXXFN Series
S-8541A18FN-IGD-T2
S-8541A25FN-IGK-T2
S-8541A33FN-IGS-T2
S-8541B00FN-IMD-T2
2.2 C,D Series (oscillation frequency: 300 kHz)
Output Voltage (V)
1.8
2.5
3.3
Feed back (1.5 to 6.0)
S-8540XXXFN Series
S-8540C18FN-ICD-T2
S-8540C25FN-ICK-T2
S-8540C33FN-ICS-T2
S-8540D00FN-IMB-T2
S-8541XXXFN Series
S-8541C18FN-IID-T2
S-8541C25FN-IIK-T2
S-8541C33FN-IIS-T2
S-8541D00FN-IME-T2
When another output voltage product is needed, please contact SII sales office.
2
Seiko Instruments Inc.
PWM Control & PWM/PFM Control High-Frequency Step-Down Switching Regulator-Controllers
S-8540/8541 Series
Rev.1.1
_70
Pin Assignment
8-Pin MSOP
Top view
1
2
3
4
8
7
6
5
Pin No.
1
2
3
4
5
Figure 2
6
7
8
Pin Name
Function
VSS
GND pin
EXT
Connection pin for external transistor
VIN
IC power supply pin
Bypass capacitor connection pin for
CVREF
reference voltage source
Power-off pin
ON/ OFF Soft-start capacitor connection pin
•
Normal operation (Step-down operation)
•
All circuit halts (No step-down operation)
Fixed output pin; None connected
NC
(FB)
[Feed back type; Feed back pin]
VOUT Output voltage pin
SENSE Current limit detection pin
Absolute Maximum Ratings
(Ta
=
25°C, unless otherwise specified)
Ratings
Units
V
SS
−0.3
to V
SS
+12
V
SS
−0.3
to V
IN
+0.3
V
SS
−0.3
to V
SS
+12
V
SS
−0.3
to V
SS
+12
V
SS
−0.3
to V
SS
+12
V
SS
−0.3
to V
SS
+12
V
SS
−0.3
to V
IN
+0.3
±100
300
−40
to 85
−40
to 125
V
V
V
V
V
V
V
mA
mW
°C
°C
Item
VIN pin voltage
CVREF pin voltage
ON/OFF pin voltage
FB pin voltage
*1
Symbol
V
IN
V
CVREF
V
ON/OFF
V
FB
V
OUT
V
SENSE
V
EXT
I
EXT
P
D
T
opr
T
stg
VOUT pin voltage
SENSE pin voltage
EXT pin voltage
EXT pin current
Power dissipation
Operating temperature range
Storage temperature range
*1.
Feed back type
Caution The absolute maximum ratings are rated values exceeding which the product could
suffer physical damage. These values must therefore not be exceeded under any
conditions.
Seiko Instruments Inc.
3
PWM Control & PWM/PFM Control High-Frequency Step-Down Switching Regulator-Controllers
S-8540/8541 Series
Rev.1.1
_70
Electrical Characteristics
1. S-8540/41A, C
(Ta
=
25
°C,
unless otherwise specified)
Parameter
Output voltage
*1
Input voltage
Current consumption 1
Current consumption
during power off
EXT pin output current
Line regulation
Load regulation
Output voltage
temperature coefficient
Oscillation frequency
Maximum duty ratio
PWM/PFM-control
switch duty ratio
*2
Current limit detection
voltage
SENSE pin input
current
Power-Off pin
input voltage
Power-Off pin
input leakage current
Soft-Start time
Efficiency
Symbol
V
OUT
(E)
V
IN
I
SS1
I
SSS
I
EXTH
I
EXTL
∆V
OUT1
∆V
OUT2
∆
V
OUT
∆
Ta
•
V
OUT
Conditions
V
IN
=
V
OUT
(S)
×
1.5
I
OUT
=
120 mA
−
V
IN
=
V
OUT
(S)
×
1.5
100
%
duty ratio
S-8540/41AXX
S-8540/41CXX
Min.
V
OUT
(S)
×
0.980
2.5
−
−
−
−32
45
−
−
−
510
255
100
19
100
6.7
2.3
−
−0.1
−0.1
7.0
−
Typ.
V
OUT
(S)
−
180
140
−
−48
66
30
30
±100
600
300
−
29
125
11.2
−
−
−
−
12.0
90
Max.
V
OUT
(S)
×
1.020
10.0
300
240
1.0
−
−
60
60
−
690
345
−
39
150
16.8
−
0.3
0.1
0.1
17.0
−
Units
V
V
µA
µA
mA
mA
mV
mV
ppm/
°C
kHz
%
%
mV
µA
V
V
µA
µA
ms
%
Circui
t
2
1
1
1
1
1
2
2
2
2
2
2
1
1
2
1
1
1
2
2
fosc
MaxDuty
PFM Duty
V
SENSE
I
SENSE
V
SH
V
SL
I
SH
I
SL
T
SS
EFFI
V
ON/OFF
=
0 V
V
OUT
=
V
OUT
(S)
×
0.95
V
IN
=10
V, V
EXT
=
V
IN
−0.2
V
V
IN
=10
V, V
EXT
=
0.2 V
V
OUT
(S)
×1.1 ≤
V
IN
≤
10 V, I
OUT
=
120 mA
V
IN
=V
OUT
(S)
×1.5,
10
µA ≤
I
OUT
≤
150 mA
V
IN
=V
OUT
(S)×1.5, I
OUT
=
120 mA
−40°C ≤
Ta
≤
85°C
Measure waveform
S-8540/41AXX
at the EXT pin.
S-8540/41CXX
Measure waveform at the EXT pin.
V
IN
=
V
OUT
(S)
×
1.5, No load
V
IN
=
V
OUT
(S)
×
1.5,
Measure waveform at the EXT pin.
V
IN
=
V
OUT
(S)
×
1.5, V
SENSE
=
V
IN
−0.1
V
V
IN
=
V
OUT
(S)
×
1.5, Judge V
OUT
(S)
×
0.98.
V
IN
=
V
OUT
(S)
×
1.5, Judge CVREF pin "L".
V
IN
=
V
OUT
(S)
×
1.5, V
ON/OFF
=
V
OUT
V
IN
=
V
OUT
(S)
×
1.5, V
ON/OFF
=
0 V
Time until V
OUT
(E) reaches 90
%
or higher of the setting
−
Condition: Recommended parts are used unless otherwise specified.
V
IN
=V
OUT
(S)×1.5(V), I
OUT
=120(mA)
(When V
OUT
(S)
≤
1.6 V, then V
IN
=
2.5 V)
*1.
V
OUT
(S) : Specified output voltage value
V
OUT
(E) : Actual output voltage value
*2.
Applied to the S-8541 series only
External components
Coil (L):
Diode (SD):
Output capacitor (C
OUT
):
Input capacitor (C
IN
):
Transistor (P
SW
):
Base resistor (R
b
):
Base capacitor (C
b
):
C
VL
:
C
SS
:
R
SS
:
R
SENSE
:
Sumida Electric Co., Ltd. CDRH6D28-100
Panasonic MA2Q737 (Schottky diode)
Nichicon Corporation F93 (16 V, 47
µF,
tantalum)
Nichicon Corporation F93 (16 V, 47
µF,
tantalum)
Toshiba Corporation 2SA1213
100 mΩ
2200 pF
1.0
µF
0.047
µF
220 kΩ
100 mΩ
Note: Line regulation and load regulation may change greatly due to GND wiring when V
IN
is high.
In the S-8540 series (PWM control), a state in which the duty ratio 0
%
continues for several clocks may occur when the input voltage
is high and the output current is low. In this case, the operation changes to the pseudo PFM mode, but the ripple voltage hardly
increases.
4
Seiko Instruments Inc.
PWM Control & PWM/PFM Control High-Frequency Step-Down Switching Regulator-Controllers
S-8540/8541 Series
Rev.1.1
_70
2. S-8540/41B,D
(Ta=25°C,unless otherwise specified)
Parameter
Output voltage
*1, *2
Symbol
V
OUT
(E)
V
IN
I
SS1
I
SSS
I
EXTH
I
EXTL
∆V
OUT1
∆V
OUT2
∆
V
OUT
∆
Ta
•
V
OUT
Conditions
V
IN
=
4.5 V
I
OUT
=
120 mA
S-8540/41B00
V
IN
=
4.5 V
S-8540/41D00
100
%
duty ratio
V
ON/OFF
=
0 V
V
OUT
=
V
OUT
(S)
×
0.95
V
IN
=10
V, V
EXT
=
V
IN
−0.2
V
V
IN
=10
V, V
EXT
=
0.2 V
3.3
≤
V
IN
≤
10 V, I
OUT
=120
mA
10
µA ≤
I
OUT
≤
150 mA
V
IN
=V
OUT
(S)×1.5, I
OUT
=120
mA
−40°C ≤
Ta
≤
85°C
Measure waveform at
S-8540/41B00
the EXT pin.
S-8540/41D00
Measure waveform at the EXT pin.
V
IN
=
V
OUT
(S)
×
1.5 V, No load
V
IN
=
4.5 V, Measure waveform at the EXT pin.
V
IN
=
4.5 V, V
SENSE
=
V
IN
−0.1
V
V
IN
=
4.5 V, Judge V
OUT
(S)
×
0.98.
V
IN
=
4.5 V, Judge CVREF pin "L".
V
IN
=
4.5 V, V
ON/OFF
=
V
OUT
V
IN
=
4.5 V, V
ON/OFF
=
0 V
Time until V
OUT
(E) reaches 90
%
or higher of the setting
−
−
Input voltage
Current consumption 1
Current consumption
during power off
EXT pin output current
Line regulation
Load regulation
Output voltage
temperature coefficient
Oscillation frequency
Maximum duty ratio
PWM/PFM-control
switch duty ratio
*3
Current limit detection
voltage
SENSE pin input
current
Power-Off pin
input voltage
Power-Off pin
input leakage current
Soft-Start time
Efficiency
Min.
V
OUT
(S)
×0.980
2.5
−
−
−
−32
45
−
−
−
510
255
100
19
100
6.7
2.3
−
−0.1
−0.1
7.0
−
Typ.
V
OUT
(S)
=3.000
−
180
140
−
−48
66
30
30
±100
600
300
−
29
125
11.2
−
−
−
−
12.0
90
Max.
V
OUT
(S)
×1.020
10.0
300
240
1.0
−
−
60
60
−
690
345
−
39
150
16.8
−
0.3
0.1
0.1
17.0
−
Units
V
V
µA
µA
mA
mA
mV
mV
ppm/
°C
kHz
%
%
mV
µA
V
V
µA
µA
ms
%
Circuit
4
3
3
3
3
3
4
4
4
4
4
4
3
3
4
3
3
3
4
4
fosc
MaxDuty
PFM Duty
V
SENSE
I
SENSE
V
SH
V
SL
I
SH
I
SL
T
SS
EFFI
Condition:
Connect recommended parts unless otherwise specified. V
IN
=V
OUT
(S)×1.5(V), I
OUT
=120(mA)
*1.
V
OUT
(S) : Specified output voltage value
V
OUT
(E) : Actual output voltage value
*2.
The typical value (specified output voltage value) is V
OUT
(S)
=
1+R
A
/R
B
=3.0(V).
See “Output Voltage adjustment”.
*3.
S-8541 series only
External components
Coil (L):
Diode (SD):
Output capacitor (C
OUT
):
Input capacitor (C
IN
):
Transistor (P
SW
):
Base resistor (R
b
):
Base capacitor (C
b
):
C
VL
:
C
SS
:
R
SS
:
R
SENSE
:
R
A
:
R
B
:
C
FB
:
Sumida Electric Co., Ltd. CDRH6D28-100
Panasonic MA2Q737 (Schottky diode)
Nichicon Corporation F93 (16 V, 47
µF,
tantalum)
Nichicon Corporation F93 (16 V, 47
µF,
tantalum)
Toshiba Corporation 2SA1213
100 mΩ
2200 pF
1.0
µF
0.047
µF
220 kΩ
100 mΩ
200 kΩ
100 kΩ
50 pF
Note: Line regulation and load regulation may change greatly due to GND wiring when V
IN
is high.
In the S-8540 series (PWM control), a state in which the duty ratio 0% continues for several clocks may occur when the input voltage
is high and the output current is low. In this case, the operation changes to the pseudo PFM mode, but the ripple voltage hardly
increases.
Seiko Instruments Inc.
5
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