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PDF S-8460 Data sheet ( Hoja de datos )
| Número de pieza | S-8460 | |
| Descripción | PWM CONTROL SWITCHING REGULATOR CONTROLLER | |
| Fabricantes | Seiko Instruments | |
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Rev.2.0_00
STEP-UP OR DOWN, SINGLE-COIL, PWM CONTROL
SWITCHING REGULATOR CONTROLLER
S-8460
The S-8460 is a PWM control CMOS step-up and step-down
switching regulator controller which consists of an automatic-selection
control circuit for step-up and step-down, a reference voltage circuit,
an oscillation circuit, an error amplifier, a phase compensation circuit,
etc. The automatic-selection control circuit for step-up and step-
down in PWM control realizes a high performance step-up and step-
down switching regulator operating on one coil. With an external N-
channel power MOS, the S-8460 is ideal for applications requiring
high efficiency and a high current output.
The S-8460 realizes low ripple, high efficiency and excellent
characteristics by featuring a PWM switching controller that can
change the duty ratio linearly from 0%, and the optimized error
amplifier and phase compensation circuit.
Features
• Single-coil, step-up or step-down switching realizes high efficiency.
• High efficiency is realized by using only N-channel power MOS FET as an external power MOS
• Synchronous rectification at step-down operation
• Input voltage :
2.2 to 18.0 V
• Variable output voltage :
Output voltage range 2.5 to 6.0 V
• Automatic-recovery overload protection circuit
• Oscillation frequency :
300 kHz
• Soft-start function set by an external capacitor (CSS)
• Shutdown function
• Lead-free products
Applications
• Power supplies for portable equipments such as PDAs, electronic notebooks, cellular phones.
• Main or local power supplies for notebook PCs and peripherals.
• Constant voltage power supplies for cameras, VCRs, and communication devices.
• Available from 2 dry battery cells and 1 lithium cell to AC adapter.
Package
Package Name
16-Pin TSSOP
Package
FT016-A
Drawing Code
Tape
FT016-A
Reel
FT016-A
Seiko Instruments Inc.
1
1 page  
STEP-UP OR DOWN, SINGLE-COIL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.2.0_00
S-8460
Electrical Characteristics
Table 3
(Unless otherwise specified : VIN = 5.0 V, IOUT = 66 mA, output voltage is set to 3.3 V, Ta = 25°C)
Parameter
Symbol
Conditions
Min.
Typ.
Max.
Unit
Measurement
Circuit
Output voltage at step-down
Output voltage at step-up
Input voltage
VOUTD
VOUTU
VIN
Current consumption 1
ISS1
VIN = 4.95 V
VIN = 2.64 V
−
No external parts, VOUT = 3.3 V × 0.95 V
(step-up mode at MaxDuty)
3.234 3.3 3.366
3.234 3.3 3.366
2.2 − 18.0
− 900 1380
V
V
V
µA
2
2
2
1
Current consumption 2
ISS2
No external parts, VOUT = 3.3 V + 0.5 V
(step-down mode at 0% Duty)
− 75 150 µA
1
Current consumption at
shutdown
ISSS
VON/OFF = 0 V
− 0.5 2.0 µA
1
VL pin output voltage
EXT1, 2, 3 pin output current
VL
IEXT1, 2, 3H
IEXT1, 2, 3L
Line regulation
∆VOUT1
The same condition as ISS2
VVL = 4.5 V, VEXT1, 2, 3 = VVL − 0.2
VEXT1, 2, 3 = 0.2 V
VIN = 2.2 to 18.0 V
4.32
30
40
−
4.50 4.68
40 −
60 −
VOUTD VOUTD
× 1.0% × 2.0%
V
mA
mA
V
1
1
1
2
Load regulation
Output voltage temperature
coefficient
∆VOUT2
∆VOUT
∆Ta • VOUT
IOUT = 10 µA to 1.25 × 66 mA
VIN = 4.95 V
Ta = −40 to +85°C
−
VOUTD VOUTD
× 1.0% × 2.0%
V
− ±100 − ppm/°C
2
−
Oscillation frequency
fOSC
The same condition as ISS1, waveform at EXT3
pin is measured.
255 300 345 kHz
1
Maximum duty ratio
MaxDuty
The same condition as ISS1, waveform at EXT3
pin is measured.
70
78
85
%
1
FB pin input current
ON/OFF pin input voltage
IFB
VSH
VSL
The same condition as ISS1
The same condition as ISS2, judged by voltage
output at VL pin.
The same condition as ISS2, judged by voltage
output at VL pin.
− 0.0 0.1 µA
1.6 − − V
− − 0.4 V
1
1
1
ON/OFF pin input leakage
current
Soft-start time
ISH
ISL
tSS
The same condition as ISS1, VON/OFF = VIN
The same condition as ISS1, VON/OFF = 0 V
The same condition as ISS1, time for EXT3 pin to
start is measured.
−0.1
−0.1
6.0
−
−
12.0
0.1
0.1
24.0
µA
µA
ms
1
1
1
Integration time of protection
circuit
tPRO
The same condition as ISS1, CSS pin : OPEN,
CPRO : 2200 pF, repeat time of CPRO pin is
measured.
1.25 2.5 5.0 ms
1
Efficiency at step-down
EFFI1
VIN = 4.95 V, IOUT = 200 to 600 mA
Efficiency at step-up
EFFI2
VIN = 2.64 V, IOUT = 50 to 400 mA
External parts Coil :
Sumida Corporation
Diode :
Matsushita Electric Industrial Co., Ltd.
Rohm Corporation
Capacitor : Nichicon Corporation
Transistor : Fairchild Semiconductor Corporation
CVL :
CSS :
CPRO :
CBST :
RFB1 :
RFB2 :
Cfzfb :
4.7 µF (ceramic)
4700 pF
2200 pF
0.1 µF
230 kΩ
100 kΩ
330 pF
− 87 −
− 83 −
CDRH104R (22 µH)
MA2Q737 (Schottky)
RB411D (Schottky)
F93 (16 V, 47 µF, tantalum) × 4
FDN337N × 3
%
%
2
2
Seiko Instruments Inc.
5
5 Page 
STEP-UP OR DOWN, SINGLE-COIL, PWM CONTROL SWITCHING REGULATOR CONTROLLER
Rev.2.0_00
S-8460
ON/OFF
VIN
ON/OFF Pin
CR Oscillation
Circuit
All EXT Pin
Voltage
Output Voltage
“H” Active
− Set value
“L” Non-active VSS
Open
VSS
Figure 12 ON/OFF Pin Structure
4. Overload Protection Circuit
The S-8460 contains a built-in overload protection circuit.
When the output voltage falls because of an overload despite the step-up operation or step-down, the S-8460
enters the step-up operation and holds the maximum duty step-up operation. If this maximum duty state lasts
longer than the overload detection time (tPRO), the overload protection circuit will hold the pins EXT1 to EXT3 at “L”
to protect the switching transistors and the inductor. When the overload protection circuit works, the output
voltage (VOUT) rises slowly since a soft start is carried out in the reference voltage circuit in the IC to raise the
reference voltage slowly from 0 V. If the load is still heavy at this time and the maximum duty step-up operation
lasts longer than tPRO, the overload protection circuit will work again. Repeat of this process leads to an operation
of intermittent mode. If the overload state is eliminated, the S-8460 goes back to the normal operation.
tPRO is determined by the external capacitor (CPRO). The approximate value of tPRO, which is from the beginning of
the maximum duty operation to the instant at which pin voltage of the EXT1 to EXT3 is held “L” to protect switching
transistors, is expressed by the following equation.
tPRO [ms] = 0.0011 × CPRO [pF]
External Parts Selection
1. Inductor
The inductance value (L value) greatly affects the maximum output current (IOUT) and the efficiency (η).
As the L value is reduced gradually, the peak current (IPK) increases, the stability of the circuit is improved, and the
output current IOUT increases. As the L value is made even smaller, IOUT decreases since the current driveability of
the switching transistor is insufficient.
As the L value is increased, the dissipation in the switching transistor due to IPK decreases, and the efficiency
reaches the maximum at a certain L value. As the L value is made even larger, the efficiency degrades since the
dissipation due to the series resistance of the coil increases. IOUT also decreases.
An inductance of 22 µH is recommended for the S-8460.
When choosing an inductor, attention to its allowable current should be paid since the current exceeding the
allowable value will cause magnetic saturation in the inductor, leading to a marked decline in efficiency and
breakdown of the IC due to large current.
An inductor should therefore be selected so as not the peak current IPK to surpass its allowable current. IPK is
represented by the following equations in step-up operation and in step-down operation. Comparing each
calculation result for step-up and step-down, larger value should be taken as the IPK. Adding some margin to the
obtained result, an inductor with the allowable current can be thus chosen.
Seiko Instruments Inc.
11
11 Page | ||
| Páginas | Total 30 Páginas | |
| PDF Descargar | [ Datasheet S-8460.PDF ] | |
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