S-8540/8541 Series
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM
SWITCHABLE SWITCHING REGULATOR CONTROLLER
www.ablicinc.com
N
Rev.4.0_02
DE
SI
G
© ABLIC Inc., 2000-2010
NE
W
The S-8540/8541 Series is a family of CMOS step-down switching regulator controllers with PWM control (S8540 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
R
FO
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 RSENSE.
Time is set by a capacitor CSS and a resistor RSS.
MM
EN
DE
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
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%
D
Oscillation frequency
*1. Refer to “ Product Name Structure” for details.
Applications
CO
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.
RE
Package
NO
T
8-Pin MSOP
1
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Block Diagrams
Pch Power
MOS FET
N
A, C types (fixed output voltage)
RSENSE
L
VIN
Power for IC
SENSE
Triangular wave
oscillation circuit
125 mV
PWM comparator
VIN
DE
SI
G
1.
Phase
compensation
circuit
EXT
VOUT
COUT
Error amplifier
SD
CIN
VREF1.0 V
CVREF
R
CSS
Voltage/current
reference
VON/OFF
CVL
FO
RSS
VSS
NE
Shutdown soft start
circuit
ON/OFF
W
PWM or PWM / PFM
switching control
circuit
Figure 1
D
B, D types (feed back)
Pch Power
MOS FET
DE
2.
RSENSE
L
Power for IC
Triangular wave
oscillation circuit
MM
EN
VIN
PWM comparator
EXT
VIN
SD
CO
RE
NO
T
VOUT
125 mV
Phase
compensation
circuit
VOUT
CFB
RA
FB
RB
Error amplifier
PWM or PWM / PFM
switching control
circuit
CIN
2
SENSE
Shutdown soft start
circuit
ON/OFF
RSS
VON/OFF
CSS
Figure 2
VREF1.0 V
Voltage/current
reference
CVREF
CVL
COUT
VSS
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Product Name Structure
1.
DE
SI
G
N
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.
Product name
S-854x x x FN - xxx T2 x
W
Environmental code
S: Lead-free, halogen-free
G: Lead-free (for details, please contact our sales office)
IC direction in tape specifications*1
NE
Product name (abbreviation)*2
R
Package name (abbreviation)
FN: 8-Pin MSOP
FO
Output voltage*3
15 to 60
(e.g. When the output voltage is 1.5 V, it is expressed as 15.)
DE
D
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
Package
RE
2.
Refer to the taping specifications at the end of this book.
Refer to the “3. Product name list”.
00: Feed back type
CO
*1.
*2.
*3.
MM
EN
Control system
0: PWM control
1: PWM/PFM switching control
Package Name
Drawing Code
Tape
FN008-A-C-SD
Reel
FN008-A-R-SD
NO
T
8-Pin MSOP
Package
FN008-A-P-SD
3
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
3.
Product name list
3.1 A, B types (oscillation frequency: 600 kHz)
N
DE
SI
G
1.5
1.6
1.8
2.5
3.3
5.0
Feed back (1.5 to 6.0)
S-8541xxxFN Series
S-8541A16FN-IGBT2z
S-8541A18FN-IGDT2z
S-8541A25FN-IGKT2z
S-8541A33FN-IGST2z
S-8541B00FN-IMDT2z
S-8540A15FN-IAAT2z
S-8540A18FN-IADT2z
S-8540A25FN-IAKT2z
S-8540A33FN-IAST2z
S-8540A50FN-IBBT2z
S-8540B00FN-IMAT2z
W
Output Voltage (V)
Table 1
S-8540xxxFN Series
NE
3.2 C,D types (oscillation frequency: 300 kHz)
NO
T
RE
CO
MM
EN
DE
D
FO
R
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 ABLIC Inc. 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
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Pin Configuration
8
7
3
6
4
5
4
5
Figure 3
6
7
8
N
NO
T
RE
CO
MM
EN
DE
D
FO
R
*1.
DE
SI
G
1
2
Pin Name
VSS
EXT
VIN
W
TOP view
Table 3
Pin Description
GND pin
Connection pin for external transistor
IC power supply pin
Bypass capacitor connection pin for
CVREF
reference voltage source
Shutdown pin
Soft-start capacitor connection pin
ON/ OFF
Normal operation (step-down operation)
All circuit halts (no step-down operation)
None connected (A, C types)
NC*1
FB
Feed back pin (B, D types)
VOUT
Output voltage pin
SENSE
Current limit detection pin
The NC pin is electrically open.
The NC pin can be connected to VIN and VSS.
Pin No.
1
2
3
NE
8-Pin MSOP
5
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Absolute Maximum Ratings
Table 4
N
(Ta = 25 °C unless otherwise specified)
Absolute Maximum Ratings
Unit
VSS 0.3 to VSS 12
V
VSS 0.3 to VIN 0.3
V
VSS 0.3 to VSS 12
V
VSS 0.3 to VSS 12
V
VSS 0.3 to VSS 12
V
VSS 0.3 to VSS 12
V
VSS 0.3 to VIN 0.3
V
100
mA
300 (When not mounted on board)
mW
500*2
mW
40 to 85
C
40 to 125
C
VIN pin voltage
CVREF pin voltage
ON/OFF pin voltage
FB pin voltage*1
VOUT pin voltage
SENSE pin voltage
EXT pin voltage
EXT pin current
VIN
VCVREF
VON/OFF
VFB
VOUT
VSENSE
VEXT
IEXT
Power dissipation
PD
DE
SI
G
Symbol
W
Item
MM
EN
500
400
300
200
100
0
0
CO
Power dissipation PD (mW)
600
50
100
150
NO
T
RE
Ambient temperature Ta (C)
6
Figure 4
(2)
When not mounted on board
350
Power dissipation PD (mW)
When mounted on board
D
(1)
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.
DE
Caution
FO
R
NE
Operating ambient temperature
Topr
Storage temperature
Tstg
*1. Feed back type (B, D types)
*2. When mounted on board
[Mounted board]
(1) Board size : 114.3 mm 76.2 mm t1.6 mm
(2) Board name : JEDEC STANDARD51-7
300
250
200
150
100
50
0
0
50
100
150
Ambient temperature Ta (C)
Power Dissipation of Package
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Electrical Characteristics
1. S-8540/8541 Series
A, C types
Table 5
Output voltage *1
VOUT (E)
VIN = VOUT (S) 1.5, no load
VOUT
Ta VOUT
fOSC
Maximum duty ratio
PWM/PFM-control switch
*2
duty ratio
Current limit detection
voltage
SENSE pin input current
Shutdown pin
input voltage
VSENSE
VIN = VOUT (S) 1.5,
Measure waveform at the EXT pin.
VIN = VOUT (S) 1.5, VSENSE = VIN 0.1 V
VIN = VOUT (S) 1.5, Judge VOUT(S) 0.98.
VIN = VOUT (S) 1.5, Judge CVREF pin "L".
VIN = VOUT (S) 1.5, VON/OFF = VOUT
VIN = VOUT (S) 1.5, VON/OFF = 0 V
Time until VOUT (E) reaches 90% or higher of the VOUT(S)
MM
EN
ISENSE
VSH
VSL
ISH
ISL
tSS
EFFI
R
IEXTH
IEXTL
VOUT1
VOUT2
Shutdown pin
input leakage current
Soft-start time
Efficiency
Max.
Units
Measurement
Circuit
V
2
V
1
A
1
180
140
1.0
A
1
32
45
48
66
30
30
60
60
1
1
2
2
100
mA
mA
mV
mV
ppm/
°C
510
255
100
600
300
690
345
19
29
100
6.7
2.3
0.1
0.1
7.0
VOUT (S)
kHz
2
2
%
2
39
%
2
125
150
mV
1
11.2
12.0
90
16.8
0.3
0.1
0.1
17.0
A
V
V
A
A
ms
%
1
2
1
1
1
2
2
:Sumida Corporation. CDRH6D28-100
:Matsushita Electric Inducstrial Co., Ltd. MA2Q737 (Schottky diode)
:Nichicon Corporation F93 (16 V, 47 F, tantalum)
:Nichicon Corporation F93 (16 V, 47 F, tantalum)
:Toshiba Corporation 2SA1213
:100 m
:2200 pF
:1.0 F
:0.047 F
:220 k
:100 m
NO
T
RE
CO
External components
Coil (L)
Diode (SD)
Output capacitor (COUT)
Input capacitor (CIN)
Transistor (PSW)
Base resistor (Rb)
Base capacitor (Cb)
CVL
CSS
RSS
RSENSE
FO
ISSS
D
Current consumption
during shutdown
DE
ISS1
Typ.
VOUT (S)
1.020
10.0
300
240
VOUT (S)
0.980
2.5
NE
PFMDuty
Current consumption 1
Oscillation frequency
VIN = VOUT (S) 1.5
IOUT = 120 mA
MaxDuty
VIN
Line regulation
Load regulation
Output voltage temperature
coefficient
Min.
S-8540/8541Axx
VIN = VOUT (S) 1.5
100 % duty ratio
S-8540/8541Cxx
VON/OFF = 0 V
VOUT = VOUT (S) 0.95
VIN = 10 V, VEXT = VIN 0.2 V
VIN = 10 V, VEXT = 0.2 V
VOUT (S) 1.1 VIN 10 V, IOUT = 120 mA
VIN = VOUT (S) 1.5, 10 A IOUT 150 mA
VIN = VOUT (S) 1.5, IOUT = 120 mA
40 Ta 85 °C
Measure waveform at the EXT S-8540/8541Axx
pin.
S-8540/8541Cxx
Measure waveform at the EXT pin.
Input voltage
EXT pin output current
Conditions
DE
SI
G
Symbol
W
Parameter
N
(Ta = 25 C, unless otherwise specified)
Condition: Recommended parts are used unless otherwise specified.
VIN =VOUT (S) 1.5 V, IOUT = 120 mA (When VOUT (S) 1.6 V, then VIN = 2.5 V)
*1. VOUT (S) : Specified output voltage value,
*2. Applied to the S-8541 series only
VOUT (E) : Actual output voltage value
Caution 1. Line regulation and load regulation may change greatly due to GND wiring when VIN is high.
2. 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.
7
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
2. S-8540/8541 Series
B, D types
Table 6
ISSS
IEXTH
IEXTL
VOUT1
VOUT2
VOUT
Ta VOUT
Oscillation frequency
fOSC
Maximum duty ratio
PWM/PFM-control switch
duty ratio *3
Current limit detection
voltage
SENSE pin input current
Shutdown pin
input voltage
Shutdown pin
input leakage current
Soft-start time
1.0
A
3
48
66
30
30
60
60
3
3
4
4
100
mA
mA
mV
mV
ppm/
°C
510
255
100
600
300
690
345
kHz
4
%
4
19
29
39
%
4
32
45
4
VSENSE
VIN = 4.5 V, Measure waveform at the EXT pin.
100
125
150
mV
3
ISENSE
VSH
VSL
ISH
ISL
VIN = 4.5 V, VSENSE = VIN 0.1 V
VIN = 4.5 V, Judge VOUT (S) 0.98.
VIN = 4.5 V, Judge CVREF pin "L".
VIN = 4.5 V, VON/OFF = VOUT
VIN = 4.5 V, VON/OFF = 0 V
Time until VOUT (E) reaches 90% or higher of the
VOUT (S)
6.7
2.3
0.1
0.1
11.2
16.8
0.3
0.1
0.1
A
V
V
A
A
3
4
3
3
3
7.0
12.0
17.0
ms
4
90
%
4
tSS
Efficiency
External components:
R
Current consumption
during shutdown
FO
ISS1
Line regulation
Load regulation
Output voltage
temperature coefficient
N
VIN = VOUT (S) 1.5 V, no load
Current consumption 1
DE
SI
G
PFM Duty
VIN
NE
MaxDuty
S-8540/8541B00
VIN = 4.5 V
100% duty ratio
S-8540/8541D00
VON/OFF = 0 V
VOUT = VOUT (S) 0.95
VIN = 10 V, VEXT = VIN 0.2 V
VIN = 10 V, VEXT = 0.2 V
3.3 VIN 10 V, IOUT = 120 mA
10 A IOUT 150 mA
VIN = VOUT (S) 1.5, IOUT = 120 mA
40 Ta 85°C
Measure waveform at
S-8540/8541B00
the EXT pin.
S-8540/8541D00
Measure waveform at the EXT pin.
Input voltage
EXT pin output current
VIN = 4.5 V
IOUT = 120 mA
W
VOUT (E)
EFFI
D
*1, *2
Conditions
MM
EN
Output voltage
Symbol
DE
Parameter
(Ta = 25 °C,unless otherwise specified)
MeasureMin.
Typ.
Max.
Units
ment
Circuit
VOUT (S)
VOUT (S)
VOUT (S)
V
4
0.980 = 3.000 1.020
2.5
10.0
V
3
180
300
3
A
140
240
NO
T
RE
CO
Coil (L)
:Sumida Corporation CDRH6D28-100
Diode (SD)
:Matsushita Electric Inducstrial Co., Ltd. MA2Q737 (Schottky diode)
Output capacitor (COUT) :Nichicon Corporation F93 (16 V, 47 F, tantalum)
Input capacitor (CIN)
:Nichicon Corporation F93 (16 V, 47 F, tantalum)
:Toshiba Corporation 2SA1213
Transistor (PSW)
Base resistor (Rb)
:100 m
:2200 pF
Base capacitor (Cb)
CVL
:1.0 F
CSS
:0.047 F
RSS
:220 k
RSENSE
:100 m
RA
:200 k
RB
:100 k
:50 pF
CFB
Condition: Connect recommended parts unless otherwise specified. VIN =4.5 V, IOUT =120 mA
*1. VOUT (S) : Specified output voltage value, VOUT (E) : Actual output voltage value
*2. The typical value (specified output voltage value) is VOUT (S) = 1 RA/RB = 3.0 V. See “Output Voltage adjustment”.
*3. S-8541 series only
Caution 1. Line regulation and load regulation may change greatly due to GND wiring when VIN is high.
2. 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.
8
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Measurement Circuits
CVREF
A
VIN
VOUT
A
A
A
EXT
SENSE
VIN
VOUT
+
EXT
SENSE
VSS
COUT
W
Cb
+
CIN
VIN
CVL
L
SD
DE
D
VON/OFF
PSW
Rb
R
CSS
FO
RSS
CVREF
ON/OFF
RSENSE
NE
Figure 5
2.
CVL
CIN
A
VSS
A
DE
SI
G
ON/OFF
N
1.
3.
MM
EN
Figure 6
VOUT
RFB1
A
CFB
A
A
RE
4.
NO
T
RSS
VON/OFF
CFB
CSS
+
COUT
SENSE
RFB1
A
EXT
A
CVL
CIN
VSS
Figure 7
CVREF
ON/OFF
VOUT
FB
SENSE
RFB2
VIN
FB
CO
RFB2
A
CVREF
ON/OFF
VIN
EXT
PSW
Rb
Cb
+
VSS
CIN
L
RSENSE
VIN
CVL
SD
Figure 8
9
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Operation
PWM control (S-8540 Series)
DE
SI
G
1. 1
N
1. Switching control method
The S-8540 series consists of pulse width modulation (PWM) DC/DC converters. In conventional
pulse frequency modulation (PFM) DC/DC converters, pulses are skipped when they operate at low
output load current, causing the variation in the ripple frequency and the increase in the ripple voltage of
the output voltage both of which constitute inherent drawbacks to those converters.
1. 2
PWM/PFM switchover control (S-8541 Series)
NE
W
In the S-8540 series the pulse width varies in the range from 0 to 100% according to the load current,
yet ripple voltage produced by the switching can easily be removed by a filter since the switching
frequency is always constant. These converters thus provide a low-ripple voltage over wide range of
input voltage and load current. And it will be skipped to be low current consumption when the pulse
width is 0% or it is no load, input current voltage is high.
R
The S-8541 series is a DC-DC converter that automatically switches between a pulse width modulation
method (PWM) and a pulse frequency modulation method (PFM), depending on the load current, and
features low current consumption.
NO
T
RE
CO
MM
EN
DE
D
FO
The S-8541 series operates under PWM control with the pulse width duty changing from 29 to 100%
when the output load current is high. On the other hand, when the output current is low, the S-8541
series operates under PFM control with the pulse width duty fixed at 29%, and pulses are skipped
according to the load current. The oscillation circuit thus oscillates intermittently so that the resultant
lower self current consumption prevents a reduction in the efficiency when the load current is low. The
switching point from PWM control to PFM control depends on the external devices (coil, diode, etc.),
input voltage, and output voltage. This series is an especially efficient DC-DC converter at an output
current of around 100 A.
10
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
2.
Soft-start function
N
The S-8540/8541 series has a built-in soft-start circuit. This circuit enables the output voltage to rise
gradually over the specified soft-start time to suppress the overshooting of the output voltage and the
rush current from the power source when the power is switched on or the power-off pin is set to "H"
DE
SI
G
The soft-start function of this IC, however, can not suppress rush current to the load completely (Refer
to Figure 9). The rush current is affected by the input voltage and the load. Please evaluate the rush
current under the actual test condition.
S-8540A33FN (VIN VON / OFF 0 5 V)
3.0 V
W
V OU T
(1 V/div)
NE
0V
1A
FO
R
Rush current
(0.5 A/div)
0A
time (1 ms/div)
Figure 9
Waveforms of output voltage and rush current at soft-start
DE
D
The soft-start function of the IC is achieved by raising internal reference voltage gradually, which is
caused by the raising of shutdown pin voltage through RC components (RSS and CSS) connected to
shutdown pin.
MM
EN
A soft-start time (tSS) is changed by RSS, CSS and the input voltage V ON/OFF to RSS.
tSS is calculated from the following formula:
tSS [ms]=R [k] C [F] In (V ON/OFF [V] / (V ON/OFF [V] 1.8))
When RSS = 220 k, CSS = 0.047 F, V ON/OFF = 2.7 V , then
tSS = 11.4 ms.
NO
T
RE
CO
e.g.
11
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
3. ON/ OFF pin (shutdown pin)
Output Voltage
Activated
Deactivated
Set value
OPEN
W
Table 7
CR Oscillation Circuit
NE
ON / OFF Pin
“H”
“L”
DE
SI
G
N
This pin deactivates or activates the step-down operation.
When the ON / OFF pin is set to "L", the VIN voltage appears through the EXT pin, prodding the
switching transistor to go off. All the internal circuits stop working, and substantial savings in current
consumption are thus achieved.
The ON / OFF pin is configured as shown in Figure 10. Since pull-up or pull-down is not performed
internally, please avoid operating the pin in a floating state. Also, try to refrain from applying a voltage of
0.3 to 1.8 V to the pin, lest the current consumption increase. When this ON / OFF pin is not used,
leave it coupled to the VIN pin.
FO
R
VIN
ON/OFF
NO
T
RE
CO
DE
MM
EN
Figure 10
D
VSS
12
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
4.
Current limit circuit
N
The S-8540/8541 series contains a current limit circuit.
DE
SI
G
The current limit circuit is designed to prevent thermal destruction of external transistors due to overload
or magnetic saturation of the coil.
The current limit circuit can be enabled by inserting a SENSE resistor (RSENSE) between the external coil
and the output pin VOUT, and connecting the node for the SENSE resistor and the coil to the SENSE
pin.
NE
W
A current limit comparator in the IC is used to check whether the voltage between the SENSE pin and
VOUT pin reaches the current limit detection voltage (VSENSE = 125 mV (typ.) ). The current flowing
through the external transistor is limited by turning it off during the left time of the oscillation period after
detection. The transistor is turned on again at the next clock and current limit detection resumes. If
the overcurrent state still persists, the current limit circuit operates again, and the process is repeated.
If the overcurrent state is eliminated, the normal operation resumes. Slight overshoot occurs in the
output voltage when the overcurrent state is eliminated.
Current limit setting value (ILimit) is calculated by the following formula:
Vsense ( 125 mV)
Rsense
R
ILimit =
VIN vs. Ipeak in the overcurrent state
V IN vs. Ipeak
(IC: S-8540A33FN, coil: CDRH6D28-100, RS ENSE: 100 m)
MM
EN
3.0
2.5
I peak (A)
DE
4. 1
D
FO
If the change with time of the current flowing through the sense resistor is higher than the response
speed of the current limit comparator in the IC, the actual current limit value becomes higher than the
ILimit (current limit setting value) calculated by the above formula. When the voltage difference between
VIN pin and VOUT pin is large, the actual current limit value increases since the change with time of the
current flowing through the sense resistor becomes large.
2.0
1.5
CO
1.0
1.25 A
0.5
0.0
RE
2.5
4.0
5.5
7.0
8.5
10.0
V IN (V)
Figure 11
lpeak change by input voltage
NO
T
When the output voltage is approximate 1.0 V or less, the load short-circuit protection does not work,
since the current limit circuit does not operate.
When the current limit circuit is not used, remove the SENSE resistor and connect the SENSE pin to the
VSS or VOUT pin.
5.
100% duty cycle
The S-8540/8541 series operates up to the maximum duty cycle of 100%. The switching transistor is
kept on continuously to supply current to the load, when the input voltage falls below the preset output
voltage value. The output voltage in this case is equal to the subtraction of lowering causes by DC
resistance of the coil and on resistance of the switching FET from the input voltage.
Even when the duty cycle is 100%, the current limit circuit works when overcurrent flows.
13
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Selection of Series Products and Associated External Components
1.
Selecting a product
1. 1
DE
SI
G
N
The S-8540/8541 series is classified into eight types according to the way of control (PWM and
PWM/PFM switching), the oscillation frequencies, and output voltage settings (fixed and feed back).
Please select the type that suits your needs best by taking the advantage described below into account.
Control method:
Two different control methods are available: PWM control (S-8540 series) and PWM/PFM switching
control (S-8541 series).
1. 2
Oscillation frequencies:
The oscillation frequencies are selectable in 600 kHz (A and B types) or 300 kHz (C and D types).
NE
W
Because of their high oscillation frequency, the products in the A and B types allow the use of small
size inductors since the peak current decreases when the same load current flows. In addition, they
can also be used with small output capacitors. These outstanding features make the A and B types
ideal for downsized devices.
On the other hand, the C and D types, having lower oscillation frequency, are characterized by small
self-consumption current and excellent efficiency under light load.
Output voltage setting:
R
1. 3
FO
Two different types are available: fixed output (A and C types) and feed back type (B and D types).
D
Table 8 provides a rough guide for selecting a product depending on the requirements of the
application. Choose the product that has the best score ().
MM
EN
DE
Table 8
The set output voltage is fixed (1.5 to 6.0 V)
S-8540
A
B
Set an output voltage freely (1.5 to 6.0 V)
C
S-8541
D
CO
Use of small external parts is Important.
RE
NO
T
: Indispensable condition
: Superiority of requirement
: Particularly superiority of requirement
D
Low-ripple voltage is important.
Remark
C
The efficiency at 100 mA or more is important.
B
The efficiency at light load (less than 10 mA) is
important.
14
A
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
2. Inductor
DE
SI
G
N
The inductance value (L) greatly affects the maximum output current (IOUT) and the efficiency ().
The peak current (IPK) increases by decreasing L and the stability of the circuit improves and IOUT
increases. If L is made even smaller, the efficiency falls causing a decline in the current drive capacity
for the switching transistor, and IOUT decreases.
The loss of IPK by the switching transistor decreases by increasing L and the efficiency becomes
maximum at a certain L value. Increasing L further decreases the efficiency due to the loss of coil DC
resistance. IOUT also decreases.
VOUT (VIN VOUT)
2 fOSC L VIN
R
IPK IOUT
NE
W
When the inductance is large in an S-8540/8541 series product, the output voltage may grow unstable
in some cases, depending on the conditions of the input voltage, output voltage, and the load current.
Perform sufficient evaluation under the actual condition and decide an optimum inductance.
The recommended inductances are 10 H for A, B types and 22 H for C, D types.
When choosing an inductor, attention to its allowable current should be paid since the current over the
allowable value will cause magnetic saturation in the inductor, leading to a marked decline in efficiency.
An inductor should therefore be selected so as not IPK to surpass its allowable current. The peak current
(IPK) is represented by the following equation in non-continuous operation mode:
3.
FO
Where fOSC is the oscillation frequency.
Diode
Capacitors
4. 1
MM
EN
4.
DE
D
The diode to be externally coupled to the IC should be a type that meets the following conditions:
The forward voltage is low (Schottky barrier diode recommended).
The switching speed is high (50 ns max.).
The reverse direction voltage is higher than VIN.
The current rating is larger than IPK.
Capacitors (CIN, COUT)
Internal power source stabilization capacitor (CVL)
NO
T
4. 2
RE
CO
The capacitor inserted in the input side (CIN) serves to reduce the power impedance and to average
the input current for better efficiency. The CIN value should be selected according to the impedance of
the power supply. It should be 47 to 100 F, although the actual value depends on the impedance of
the power source used and load current value.
For the output side capacitor (COUT), select a large capacitance with low ESR (Equivalent Series
Resistance) to smoothen the ripple voltage. When the input voltage is extremely high or the load
current is extremely large, the output voltage may become unstable. In this case the unstable area
will become narrow by selecting a large capacitance for an output side capacitor. A tantalum
electrolytic capacitor is recommended since the unstable area widens when a capacitor with a large
ESR, such as an aluminum electrolytic capacitor, or a capacitor with a small ESR, such as a ceramic
capacitor, is chosen. The range of the capacitance should generally be 47 to 100 F.
The main circuits of the IC work on an internal power source connected to the CVREF pin. The CVL
is a bypass capacitor for stabilizing the internal Power source. CVL should be a 1 F ceramic
capacitor and wired in a short distance and at a low impedance.
15
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
5.
External transistor
Enhancement (Pch) MOS FET
DE
SI
G
5. 1
N
The S-8540/8541 series can work with an enhancement (Pch) MOS FET or a bipolar (PNP) transistor as
an external transistor.
The EXT pin can directly drive the Pch MOS FET with a gate capacity of approximate 1200 pF.
When a Pch MOS FET is chosen, efficiency will be 2 to 3 % higher than that achieved by a PNP
bipolar transistor since the MOS FET switching speed is faster than that of the bipolar transistor and
power loss due to the base current is avoided.
W
The important parameters in selecting a Pch MOS FET are the threshold voltage, breakdown voltage
between gate and source, breakdown voltage between drain and source, total gate capacity, onresistance, and the current ratings.
R
NE
The EXT pin swings from voltage VIN to VSS. When the input voltage is low, a MOS FET with a low
threshold voltage has to be used so that the MOS FET will turn on as required. When, conversely, the
input voltage is high, select a MOS FET whose gate-source breakdown voltage is higher than the
input voltage by at least several volts.
D
FO
Immediately after the power is turned on, or the power is turned off (that is, when the step-down
operation is terminated), the input voltage is applied across the drain and the source of the MOS FET.
The transistor therefore needs to have drain-source breakdown voltage that is also several volts
higher than the input voltage.
The total gate capacity and the on-resistance affect the efficiency.
DE
The power loss for charging and discharging the gate capacity by switching operation will affect the
efficiency at low load current region more when the total gate capacity becomes larger and the input
voltage becomes higher. If the efficiency at low load is a matter of concern, select a MOS FET with a
small total gate capacity.
MM
EN
In regions where the load current is high, the efficiency is affected by power loss caused by the onresistance of the MOS FET. If the efficiency under heavy load is particularly important in the
application, choose a MOS FET having on-resistance as low as possible.
NO
T
RE
CO
As for the current rating, select a MOS FET whose maximum continuous drain current rating is higher
than IPK.
16
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
5. 2
Bipolar (PNP) transistor
N
Figure 12 shows a circuit diagram using Toshiba Corporation 2SA1213-Y for the bipolar transistor
(PNP). Using a bipolar transistor, the driving capacity for increasing the output current is determined
by the hFE value and the Rb value.
DE
SI
G
2SA1213-Y
VIN
Rb
Cb
EXT
Figure 12
VIN 0.7
Ib
0.4
IEXTL
FO
Rb
R
The Rb value is given by the following equation:
NE
W
VIN
Calculate the necessary base current Ib using the hFE value of the bipolar transistor from the relation,
Ib = IPK/hFE, and select a smaller value for Rb which is calculated from the above equation.
DE
D
A small Rb value will certainly contribute to increase the output current, but it will also decrease the
efficiency. Determine the optimum value through experiment since the base current flows as pulses
and voltage drop may takes place due to the wiring resistance and so on.
MM
EN
In addition, if speed-up capacitor Cb is inserted in parallel with resistance Rb, as shown in Figure 12,
the switching loss will be reduced, leading to a higher efficiency.
by using the following equation :
Cb
1
2 Rb fOSC 0.7
NO
T
RE
CO
Select a Cb value after performing sufficient evaluation since the optimum Cb value differs depending
upon the characteristics of the bipolar transistor.
17
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Standard Circuits
1.
Fixed output voltage (Pch MOS FET)
Tr
VIN Power for IC
Triangular wave
oscillation circuit
PWM comparator
EXT
Phase
compensation
circuit
125mV
VOUT
Error amplifier
SD
PWM, PWM/PFM
switching control
circuit
CIN
VREF1.0 V
Voltage/current
reference
ON/OFF
VSS
NE
Shutdown soft start
circuit
COUT
W
VIN
SENSE
DE
SI
G
L
N
RSENSE
CVREF
FO
R
VON/OFF
One point ground
Tr
VIN
DE
Feed back type (Pch MOS FET)
RSENSE
L
oscillation circuit
PWM comparator
EXT
RE
CO
CIN
PWM, PWM/PFM
switching control
circuit
Shutdown soft start
125mV
CFB
RA
COUT
FB
Voltage/current
reference
VON/OFF
VOUT
VREF=1.0 V
circuit
ON/OFF
Phase
compensation
circuit
Error amplifier
SD
VIN
SENSE
Power for IC Triangular wave
MM
EN
2.
D
Figure 13
VSS
RB
CVREF
NO
T
One point ground
Caution
18
Figure 14
The above connection diagram and constant will not guarantees successful operation.
Perform through evaluation using the actual application to set the constant.
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Precautions
DE
SI
G
N
Install the external capacitors, diode, coil, and other peripheral components as close to the IC as possible,
and make a one-point grounding.
When the input voltage is 9 to 10 V, VOUT may vary largely according to the grounding method.
When it is difficult to make one-point grounding, use two grounds: one for VIN, CIN, and SD GND, and the
other for VOUT, VCVREF, and IC GND.
Characteristics ripple voltage and spike noise occur in IC containing switching regulators. Moreover rush
current flows at the time of a power supply injection. Because these largely depend on the inductor, the
capacitor and impedance of power supply used, fully check them using an actually mounted model.
NE
W
If the input voltage is high and output current is low, pulses with a low duty ratio may appear, and then the
0% duty ratio continues for several clocks. In this case the operation changes to the pseudo pulse
frequency modulation (PFM) mode, but the ripple voltage hardly increases.
If the input power supply voltage is lower than 1.0 V, the IC operation is unstable and the external switch
may be turned on.
R
If input power supply voltage is 10.0 V or higher, the circuit operation is unstable and the IC may be
damaged.
FO
The input voltage must be in the standard range (2.5 to 10.0 V).
The current limit circuit of the IC limits current by detecting a voltage difference of external resistor RSENSE.
In choosing the components, make sure that overcurrent will not surpass the allowable dissipation of the
switching transistor and the inductor.
DE
D
Make sure that dissipation of the switching transistor will not surpass the allowable power dissipation of the
package (especially at high temperature).
Do not apply an electrostatic discharge to this IC that exceeds the performance ratings of the built-in
electrostatic protection circuit.
NO
T
RE
CO
MM
EN
ABLIC Inc. shall bear no responsibility for any patent infringement by a product that includes an IC
manufactured by ABLIC Inc. in relation to the method of using the IC in that product, the product
specifications, or the destination country.
19
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Application Circuits
1.
External adjustment of output voltage
DE
SI
G
N
The output voltage can be adjusted or changed in the output voltage setting range (1.5 to 6.0 V) by
adding external resistors (RA, RB) and a capacitor (CFB) in the S-8540/8541B00AFN and S8540/8541D00AFN, as shown in Figure 15. Temperature gradient can be given by inserting a
thermistor in series to RA and RB.
RSENSE
L
Power for IC Triangular wave
VIN
oscillation circuit
PWM comparator
EXT
Phase
compensation
circuit
125mV
Error amplifier
SD
VREF=1.0 V
VON/OFF
CFB
RA
COUT
FB
VSS
RB
CVREF
D
ON/OFF
Voltage/current
reference
FO
Shutdown soft start
circuit
VOUT
PWM, PWM/PFM
switching control
circuit
CIN
R
VIN
NE
SENSE
W
Tr
DE
One point ground
Figure 15
MM
EN
The above connection diagram and constant will not guarantees successful operation.
Perform through evaluation using the actual application to set the constant.
NO
T
RE
CO
Caution
20
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Set the CFB so that f = 1/(2 CFB
When VOUT = 3.0 V, RA = 200 k, RB = 100 k, then CFB = 100 pF.
DE
SI
G
e.g.
RA) is 0.1 to 20 kHz (normally 10 kHz).
Add a
N
RA, RB must be RA RB 2 M and the ratio of RA to RB should be set so that the FB pin is 1.0 V.
capacitor (CFB) in parallel to RA to prevent unstable operation like output oscillation.
The precision of output voltage (VOUT) determined by RA, RB is affected by the precision of the voltage at
the FB pin (1 V 2.0%), the precision of RA and RB, current input to the FB pin, and IC power supply
voltage VDD.
0.98 V V
RBmax.
RAmax.
VOUTmax. = 1
1.02 V V
RBmin.
R
RAmin.
FO
VOUTmin. = 1
NE
W
Suppose that the FB pin input current is 0 nA, and that the maximum absolute values of the external
resistors RA and RB are RA max. and RB max, and the minimum absolute values of the external resistors
RA min. and RB min., and that the output voltage shift due to the VDD voltage
RA and RB are
dependency is V, the minimum value VOUT min. and maximum value VOUT max. of the output voltage
VOUT variation is calculated by the following formula:
DE
D
The precision of the output voltage VOUT cannot be made lower than the precision of the IC output voltage
without adjustment of external resistors RA and RB. The lower the RA/RB, the less it is affected by the
absolute value precision of the external resistors RA and RB. The lower the RA and RB, the less it is
affected by the FB pin input current.
MM
EN
To suppress the influence of FB pin input current on the variation of output voltage VOUT, the external
resistor RB value must be made sufficiently lower than the input impedance of the FB pin, 1 V/50 nA =
20 M max.
Waste current flows through external resistors RA and RB. When it is not a negligible value with respect
to load current in actual use, the efficiency decreases. The RA and RB values of the external resistors
must therefore be made sufficiently high.
CO
Evaluation of the influence of the noise is needed in the actual condition If the RA and RB values of
resistors are high (1 M or higher) since they are susceptible to external noise.
They must be
NO
T
RE
The output voltage VOUT precision and the waste current are in a trade-off relation.
considered according to application requests.
21
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Typical Characteristics
250
25°C
85°C
200
ISS1 (A)
150
150
100
100
Ta40°C
50
25°C
50
0
0
2.5
4.0
5.5
7.0
8.5
10.0
W
ISS1 (A)
200
85°C
2.5
4.0
(3) fOSC VIN
Ta40°C
7.0
8.5
10.0
8.5
10.0
VIN (V)
S-8540/8541(600 kHz)
720
85°C
680
85°C
fOSC (kHz)
R
340
320
Ta40°C
25°C
280
640
600
FO
300
560
Ta40°C
25°C
520
260
4.0
5.5
7.0
8.5
VIN (V)
100
80
Ta40°C
60
25°C
20
0
2.5
4.0
CO
40
5.5
2.5
4.0
7.0
7.0
S-8540/8541
100
80
Ta40°C
60
40
25°C
20
85°C
85°C
0
2.5
8.5
5.5
VIN (V)
(6) IEXTL VIN
S-8540/8541
MM
EN
(5) IEXTH VIN
480
10.0
DE
2.5
D
240
IEXTL (mA)
fOSC (kHz)
(4) fOSC VIN
S-8540/8541(300 kHz)
360
5.5
NE
VIN (V)
IEXTH (mA)
N
250
S-8540/8541(600 kHz)
DE
SI
G
1. Examples of major parameters characteristics
(1) ISS1 VIN S-8540/8541(300 kHz)
(2) ISS1 VIN
4.0
5.5
7.0
8.5
10.0
VIN (V)
10.0
RE
VIN (V)
(7) VSH VIN S-8540/8541
0.9
2.2
0.8
Ta40°C
2.1
2.0
VSL (V)
2.3
NO
T
VSH (V)
(8) VSL VIN S-8540/8541
25°C
1.9
1.8
0.6
25°C
0.5
85°C
0.4
85°C
1.7
0.3
2.5
4.0
5.5
7.0
VIN (V)
22
Ta40°C
0.7
8.5
10.0
2.5
4.0
5.5
7.0
VIN (V)
8.5
10.0
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
N
16
15
14
13
12
11
10
9
8
25°C
2.5
4.0
5.5
DE
SI
G
Ta40°C
85°C
7.0
8.5
10.0
W
tSS (ms)
(9) tSS VIN
VIN (V)
(11) VOUT VIN 3.3 V
PWM/PFM 600 kHz
NE
(10) VOUT VIN 1.8 V
1.85
3.40
R
VOUT (V)
FO
1.81
1.79
100 mA
400 mA
1.75
4
5.5
7
8.5
VIN (V)
PWM 600 kHz
MM
EN
(12) VOUT VIN 3.3 V
3.40
3.30
3.20
4.0
5.5
RE
2.5
CO
400 mA
3.25
2.5
7.0
5.5
7.0
8.5
10.0
(13) VOUT VIN 3.3 V
PWM/PFM 300 kHz
3.40
IOUT 0.1 mA
100 mA
3.35
3.30
400 mA
3.25
3.20
8.5
10.0
2.5
4.0
5.5
7.0
VIN (V)
8.5
10.0
NO
T
VIN (V)
4.0
VIN (V)
100 mA
IOU T 0.1 mA
3.35
400 mA
3.20
10
DE
2.5
3.30
3.25
VOUT (V)
1.77
100 mA
3.35
D
VOUT (V)
IOUT 0.1 mA
IOUT 0.1 mA
1.83
VOUT(V)
PWM/PFM 600 kHz
23
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Transient Response Characteristics
2. 1 Power-on (IOUT: no Load)
(1) S-8540A33FN (VIN: 0 4.95 V)
10 V
VIN
(2.5 V/div)
V IN
(2.5 V/div)
0V
0V
3V
3V
V OUT
(1 V/div)
0V
VOUT
(1 V/div)
0V
NE
t (2 ms/div)
(3) S-8540C33FN (VIN: 0 4.95 V)
10 V
R
FO
VIN
(2.5 V/div)
VIN
(2.5 V/div)
0V
0V
3V
D
3V
VOUT
(1 V/div)
MM
EN
t (2 ms/div)
DE
VOU T
(1 V/div)
0V
0V
t (1 ms/div)
(5) S-8540A18FN (VIN: 0 2.7 V)
VOUT
(0.5 V/div)
NO
T
0V
RE
0V
CO
10 V
2V
24
t (1 ms/div)
(4) S-8540C33FN (VIN: 0 10 V)
10 V
V IN
(2.5 V/div)
DE
SI
G
10 V
N
(2) S-8540A33FN (VIN: 0 10 V)
W
2.
t (4 ms/div)
(6) S-8540A18FN (VIN: 0 10 V)
10 V
VIN
(2.5 V/div)
0V
2V
V OUT
(0.5 V/div)
0V
t (1 ms/div)
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Shutdown pin response (VON/OFF : 0 2.5 V
(1) S-8540A33FN (VIN: 4.95V)
IOUT: no Load)
4V
N
(2) S-8540A33FN (VIN: 10V)
VON/OFF
(1 V/div)
DE
SI
G
4V
VON/OFF
(1 V/div)
0V
0V
3V
3V
VOUT
(1 V/div)
0V
VOUT
(1 V/div)
0V
W
2. 2
t (4 ms/div)
(3) S-8540C33FN (VIN: 4.95 V)
(4) S-8540C33FN (VIN: 10 V)
4V
VON/OFF
(1 V/div)
0V
VON/OF F
(1 V/div)
0V
FO
R
4V
3V
D
3V
MM
EN
t (4 ms/div)
(5) S-8540A18FN (VIN: 4.95 V)
RE
VOUT
(0.5 V/div)
0V
CO
4V
1.5 V
DE
VOUT
(1 V/div)
VOUT
(1 V/div)
0V
VON /OF F
(1 V/div)
0V
NE
t (4 ms/div)
t (4 ms/div)
(6) S-8540A18FN (VIN: 10 V)
4V
VON /OF F
(1 V/div)
0V
1.5 V
VOUT
(0.5 V/div)
0V
t (4 ms/div)
NO
T
t (4 ms/div)
0V
25
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Supply Voltage Variation (VIN: 3.69.03.6 V)
(1) S-8540A33FN (IOUT: 10 mA)
10 V
10 V
VIN
(2.5 V/div)
VIN
(2.5 V/div)
N
(2) S-8540A33FN (IOUT: 500 mA)
DE
SI
G
2. 3
0V
0V
VOUT
(0.1 V/div)
W
VOUT
(0.1 V/div)
t (0.4 ms/div)
(3) S-8540C33FN (IOUT: 10 mA)
(4) S-8540C33FN (IOUT: 500 mA)
10 V
10 V
V IN
(2.5 V/div)
FO
R
VIN
(2.5 V/div)
0V
D
0V
VOUT
(0.1 V/div)
MM
EN
(5) S-8540A18FN (IOUT: 10 mA)
10 V
VIN
(2.5 V/div)
RE
CO
0V
NO
T
t (0.4 ms/div)
26
DE
VOUT
(0.1 V/div)
t (0.4 ms/div)
VOUT
(0.1 V/div)
NE
t (0.4 ms/div)
t (0.4 ms/div)
(6) S-8540A18FN (IOUT: 500 mA)
10 V
V IN
(2.5 V/div)
0V
VOUT
(0.1 V/div)
t (0.4 ms/div)
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Load Variation (VIN: 2.7 V or 5.0 V or 7.5 V, IOUT: 0.1500 mA, 5000.1 mA)
(1) S-8540A33FN (VIN: 4.95 V)
N
(2) S-8540A33FN (VIN: 4.95 V)
500 mA
IOU T
500 mA
DE
SI
G
2. 4
0.1 mA
IOUT
0.1 mA
V OUT
(0.1 V/div)
W
VOUT
(0.1 V/div)
t (4 ms/div)
(3) S-8540C33FN(VIN: 4.95 V)
(4) S-8540C33FN(VIN: 4.95 V)
500 mA
IOUT
R
500 mA
IOUT
FO
0.1 mA
0.1 mA
VOUT
(0.1 V/div)
MM
EN
t (0.2 ms/div)
DE
D
VOUT
(0.1 V/div)
(5) S-8540A18FN (VIN: 2.7 V)
500 mA
IOU T
RE
CO
0.1 mA
VOU T
(0.1 V/div)
NE
t (0.2 ms/div)
(6) S-8540A18FN (VIN: 2.7 V)
500 mA
IOU T
0.1 mA
V OUT
(0.1 V/div)
t (4 ms/div)
NO
T
t (0.2 ms/div)
t (8 ms/div)
27
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
N
Reference Data
DE
SI
G
This reference data is intended to help you select peripheral components to be externally connected to the
IC. Therefore, this information provides recommendations on external components selected with a view to
accommodating a wide variety of IC applications. Characteristic data is duly indicated in the table below.
Table 9. External components list for efficiency
(Small and thin application using 1.3 mm or less tall components, maximum load current : IOUT = 0.9 A)
Output
No. Product Name
Modulation fOSC
Inductor
Transistor Diode Output Capacitor
Voltage
1.3
S-8540A25FN
1.4
S-8541A25FN
1.5
S-8540A18FN
1.6
S-8541A18FN
2.5 V
1.8 V
PWM/PFM
PWM
PWM/PFM
W
S-8541A33FN
PWM
NE
1.2
3.3 V
600kHz LDR655312T-4R7 CPH6301 RB491D F920J476MB 2
PWM
R
S-8540A33FN
PWM/PFM
FO
1.1
1.8
S-8541C33FN
1.9
S-8540C25FN
3.3 V
PWM
PWM/PFM
PWM
DE
S-8540C33FN
MM
EN
1.7
D
Table 10 External components list for efficiency
(High efficiency application using 3.0mm or less tall components, maximum load current : IOUT = 1.0 A)
Output
No. Product Name
Modulation fOSC
Inductor
Transistor Diode Output Capacitor
Voltage
2.5 V
1.10 S-8541C25FN
1.11 S-8540C18FN
1.8 V
1.12 S-8541C18FN
PWM/PFM
300kHz
CDRH6D28-220
CPH6301 RB491D F931A476MC 1
PWM
PWM/PFM
Product
Name
2.1
S-8540A33FN
2.2
S-8541A33FN
2.3
S-8540A18FN
NO
T
2.4
S-8541A18FN
2.5
S-8540C33FN
2.6
S-8541C33FN
2.7
S-8540C18FN
2.8
S-8541C18FN
28
Output
Modulation
Voltage
RE
No.
CO
Table 11 External components list for ripple voltage
3.3 V
1.8 V
3.3 V
1.8 V
fOSC
Inductor
Transistor
Diode
Output
Capacitor
PWM
PWM/PFM
PWM
600kHz LDR655312T-4R7 CPH6301 RB491D F920J476MB 2
PWM/PFM
PWM
PWM/PFM
PWM
PWM/PFM
300kHz
CDRH6D28-220
CPH6301 RB491D F931A476MC 1
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Table 12 External parts function
Inductor
CDRH6D28-220
Diode
RB491D
4.7 H
0.19
22.0 H
0.128
Maximum
Current
Size (L W H)
[mm]
N
DC
Resistance
0.9 A
6.5 5. 3 1.25
1.2 A
7.0 7.0 3.0
Forward current 1.0 A at VF = 0.45 V,
Vrm = 25V
3.0 3.1 1.3
47 F, 6.3 V
3.6 3.0 1.2
47 F, 10.0 V
Vdss =20 V max., Vgss =10 V max.,
ID =3.0 A max., Ciss =360 pF, Ron =110 m
6.2 3.4 2.7
2.9 2.8 0.9
NO
T
RE
CO
MM
EN
DE
D
FO
R
Output
F920J476MB
Capacity
(tantalum
F931A476MC
electrolytic)
Transistor
CPH6301
(MOS FET)
TDK
Corporation
Sumida
Corporation
Rohm
Corporation
Nichicon
Corporation
Nichicon
Corporation
Sanyo Electric
Co., Ltd.
L-Value
DE
SI
G
LDR655312T-4R7
Manufacturer
W
Product Name
NE
Component
29
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
Efficiency Characteristics : Efficiency () Output current (IOUT)
S-8540A33FN
S-8541A33FN
N
100
(3.3 V, 600 kHz, PWM/PFM control)
100
V IN4.0 V
90
80
5.0 V
70
7.2 V
60
50
1
10
100
1000
DE
SI
G
Efficiency (%)
1. 2
(3.3 V, 600 kHz, PWM control)
VIN4.0 V
90
80
70
5.0 V
60
50
1
I OUT (mA)
1. 4
10
100
S-8540A18FN
FO
(1.8 V, 600 kHz, PWM control)
100
VIN2.5 V
90
CO
80
70
50
1
RE
3.6 V
60
VIN3.0 V
80
70
3.6 V
5.0 V
10
NO
T
I OUT (mA)
100
60
50
1000
MM
EN
1. 5
90
D
1
IOUT (mA)
Efficiency (%)
5.0 V
60
50
30
Efficiency (%)
80
3.6 V
(2.5 V, 600 kHz, PWM/PFMcontrol)
100
DE
Efficiency (%)
V IN3.0 V
70
1000
S-8541A25FN
R
(2.5 V, 600 kHz, PWM control)
90
100
NE
S-8540A25FN
100
10
7.2 V
IOUT (mA)
5.0 V
1000
1
10
100
1000
IOUT (mA)
1. 6
S-8541A18FN
(1.8 V, 600 kHz, PWM/PFM control)
100
Efficiency (%)
1. 3
W
1. 1
Efficiency (%)
1.
VIN2.5 V
90
80
70
3.6 V
5.0 V
60
50
1
10
100
IOUT (mA)
1000
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
5.0 V
7.2 V
60
50
1
10
100
1000
VIN 4.0 V
90
80
70
5.0 V 7.2 V
60
50
1
10
W
80
70
(3.3 V, 300 kHz, PWM/PFM control)
100
VI N4.0 V
90
S-8541C33FN
1. 10
(2.5 V, 300 kHz, PWM control)
3.6 V
10
100
IOUT (mA)
3.6 V
5.0 V
50
1
CO
70
60
R
60
50
1
10
1000
100
1000
S-8541C18FN
(1.8 V,300 kHz, PWM/PFM control)
100
VIN 2.5 V
90
80
3.6 V
70
5.0 V
60
50
1
10
100
1000
IOUT (mA)
NO
T
IOUT (mA)
100
10
IOUT (mA)
Efficiency (%)
80
RE
Efficiency (%)
VIN 2.5 V
90
5.0 V
3.6 V
70
1. 12
(1.8 V, 300 kHz, PWM control)
100
80
1000
MM
EN
S-8540C18FN
VIN 3.0 V
90
D
60
1
(2.5 V, 300 kHz, PWM/PFM control)
FO
5.0 V
70
50
1. 11
Efficiency (%)
80
S-8541C25FN
100
DE
Efficiency (%)
VIN3.0 V
90
1000
NE
S-8540C25FN
100
100
IOUT (mA)
IOUT (mA)
1. 9
N
(3.3 V, 300 kHz, PWM control)
100
Efficiency (%)
1. 8
DE
SI
G
S-8540C33FN
Efficiency (%)
1. 7
31
STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_02
S-8540/8541 Series
2. Ripple Voltage (Vrip) Output Current (IOUT) Characteristics
2. 1 S-8540A33FN
2. 2 S-8541A33FN
(3.3 V, 600 kHz, PWM control)
Ripple (mV)
5.0 V
V IN4.0 V
60
40
5.0 V
40
20
1
10
100
0
1000
1
Ripple (mV)
5.0 V
60
3.6 V
VIN2.5 V
40
20
10
100
1000
DE
IOUT (mA)
MM
EN
80
3.6 V
VIN2.5 V
60
40
1
CO
20
5.0 V
10
100
1
10
100
S-8541C33FN
(3.3 V, 600 kHz, PWM/PFM control)
100
80
60
VIN 2.5 V
20
0
1000
1
10
RE
40
3.6 V
V IN2.5 V
5.0 V
20
0
1
(1.8 V, 300 kHz, PWM/PFM control)
100
80
60
V IN2.5 V
40
3.6 V
5.0 V
20
10
100
IOUT (mA)
32
1000
S-8541C18FN
Ripple (mV)
NO
T
Ripple (mV)
2. 8
(1.8 V, 300 kHz, PWM control)
60
100
IOUT (mA)
S-8540C18FN
80
3.6 V
5.0 V
40
IOUT (mA)
100
1000
IOUT (mA)
2. 6
(3.3 V, 600 kHz, PWM control)
100
0
0
D
1
S-8540C33FN
2. 7
5.0 V
FO
V IN2.5 V
20
Ripple (mV)
80
(1.8 V, 600 kHz, PWM/PFM control)
R
3.6 V
60
2. 5
W
100
80
0
1000
S-8541A18FN
Ripple (mV)
Ripple (mV)
2. 4
(1.8 V, 600 kHz, PWM control)
40
100
NE
S-8540A18FN
100
10
IOUT (mA)
IOUT (mA)
2. 3
7.2 V
V IN4.0 V
60
20
0
N
80
DE
SI
G
7.2 V
80
(3.3 V, 600 kHz, PWM/PFM control)
100
Ripple (mV)
100
1000
0
1
10
100
IOUT (mA)
1000
5
1
4
NE
W
8
DE
SI
G
N
2.95±0.2
D
FO
R
0.13±0.1
MM
EN
DE
0.2±0.1
0.65±0.1
NO
T
RE
CO
No. FN008-A-P-SD-1.2
TITLE
MSOP8-A-PKG Dimensions
No.
FN008-A-P-SD-1.2
ANGLE
UNIT
mm
ABLIC Inc.
2.0±0.05
4.0±0.1
1.35±0.15
4.0±0.1
NE
W
DE
SI
G
N
1.55±0.05
1.05±0.05
R
0.3±0.05
1
5
8
Feed direction
CO
MM
EN
4
DE
D
FO
3.1±0.15
NO
T
RE
No. FN008-A-C-SD-1.1
TITLE
MSOP8-A-Carrier Tape
FN008-A-C-SD-1.1
No.
ANGLE
UNIT
mm
ABLIC Inc.
FO
R
NE
W
DE
SI
G
N
16.5max.
13.0±0.3
MM
EN
DE
D
Enlarged drawing in the central part
(60°)
CO
(60°)
NO
T
RE
No. FN008-A-R-SD-1.1
MSOP8-A-Reel
TITLE
No.
FN008-A-R-SD-1.1
ANGLE
QTY.
UNIT
mm
ABLIC Inc.
3,000
Disclaimers (Handling Precautions)
All the information described herein (product data, specifications, figures, tables, programs, algorithms and application
circuit examples, etc.) is current as of publishing date of this document and is subject to change without notice.
2.
The circuit examples and the usages described herein are for reference only, and do not guarantee the success of
any specific mass-production design.
ABLIC Inc. is not responsible for damages caused by the reasons other than the products described herein
(hereinafter "the products") or infringement of third-party intellectual property right and any other right due to the use
of the information described herein.
3.
ABLIC Inc. is not responsible for damages caused by the incorrect information described herein.
4.
Be careful to use the products within their specified ranges. Pay special attention to the absolute maximum ratings,
operation voltage range and electrical characteristics, etc.
ABLIC Inc. is not responsible for damages caused by failures and / or accidents, etc. that occur due to the use of the
products outside their specified ranges.
5.
When using the products, confirm their applications, and the laws and regulations of the region or country where they
are used and verify suitability, safety and other factors for the intended use.
6.
When exporting the products, comply with the Foreign Exchange and Foreign Trade Act and all other export-related
laws, and follow the required procedures.
7.
The products must not be used or provided (exported) for the purposes of the development of weapons of mass
destruction or military use. ABLIC Inc. is not responsible for any provision (export) to those whose purpose is to
develop, manufacture, use or store nuclear, biological or chemical weapons, missiles, or other military use.
8.
The products are not designed to be used as part of any device or equipment that may affect the human body, human
life, or assets (such as medical equipment, disaster prevention systems, security systems, combustion control
systems, infrastructure control systems, vehicle equipment, traffic systems, in-vehicle equipment, aviation equipment,
aerospace equipment, and nuclear-related equipment), excluding when specified for in-vehicle use or other uses. Do
not apply the products to the above listed devices and equipments without prior written permission by ABLIC Inc.
Especially, the products cannot be used for life support devices, devices implanted in the human body and devices
that directly affect human life, etc.
Prior consultation with our sales office is required when considering the above uses.
ABLIC Inc. is not responsible for damages caused by unauthorized or unspecified use of our products.
9.
Semiconductor products may fail or malfunction with some probability.
The user of the products should therefore take responsibility to give thorough consideration to safety design including
redundancy, fire spread prevention measures, and malfunction prevention to prevent accidents causing injury or
death, fires and social damage, etc. that may ensue from the products' failure or malfunction.
The entire system must be sufficiently evaluated and applied on customer's own responsibility.
MM
EN
DE
D
FO
R
NE
W
DE
SI
G
N
1.
10. The products are not designed to be radiation-proof. The necessary radiation measures should be taken in the
product design by the customer depending on the intended use.
CO
11. The products do not affect human health under normal use. However, they contain chemical substances and heavy
metals and should therefore not be put in the mouth. The fracture surfaces of wafers and chips may be sharp. Be
careful when handling these with the bare hands to prevent injuries, etc.
12. When disposing of the products, comply with the laws and ordinances of the country or region where they are used.
RE
13. The information described herein contains copyright information and know-how of ABLIC Inc.
The information described herein does not convey any license under any intellectual property rights or any other
rights belonging to ABLIC Inc. or a third party. Reproduction or copying of the information from this document or any
part of this document described herein for the purpose of disclosing it to a third-party without the express permission
of ABLIC Inc. is strictly prohibited.
NO
T
14. For more details on the information described herein, contact our sales office.
2.0-2018.01
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