STEP-DOWN, 600 kHz PWM CONTROL or PWM/PFM SWITCHABLE SWITCHING REGULATOR CONTROLLER
Rev.4.0_00
S-8540/8541 Series
Seiko Instruments Inc. 7
Electrical Characteristics
1. S-8540/8541 Series A, C types
Table 5
(Ta = 25 °C, unless otherwise specified)
Parameter Symbol Conditions Min. Typ. Max. Units
Measure-
ment
Circuit
Output voltage
*1
V
OUT (E)
V
IN
= V
OUT (S)
×
1.5
I
OUT
= 120 mA
V
OUT (S)
×
0.980
V
OUT (S)
V
OUT (S)
×
1.020
V 2
Input voltage V
IN
−
2.5
−
10.0 V 1
S-8540/8541Axx
−
180 300
Current consumption 1 I
SS1
V
IN
= V
OUT (S)
×
1.5
100 % duty ratio
S-8540/8541Cxx
−
140 240
μ
A 1
Current consumption
during shutdown
I
SSS
V
ON/OFF
= 0 V
V
OUT
= V
OUT (S)
×
0.95
−
−
1.0
μ
A 1
I
EXTH
V
IN
= 10 V, V
EXT
= V
IN
−
0.2 V
−
32
−
48
−
mA 1
EXT pin output current
I
EXTL
V
IN
= 10 V, V
EXT
= 0.2 V 45 66
−
mA 1
Line regulation
Δ
V
OUT1
V
OUT (S)
×
1.1
≤
V
IN
≤
10 V, I
OUT
= 120 mA
−
30 60 mV 2
Load regulation
Δ
V
OUT2
V
IN
= V
OUT (S)
×
1.5, 10
μ
A
≤
I
OUT
≤
150 mA
−
30 60 mV 2
Output voltage temperature
coefficient
Δ
Δ
V
Ta V
OUT
OUT
•
V
IN
= V
OUT (S)
×
1.5, I
OUT
= 120 mA
−
40
≤
Ta
≤
+
85 °C
−
±
100
−
ppm/
°C
2
S-8540/8541Axx 510 600 690 2
Oscillation frequency f
OSC
Measure waveform at the EXT
pin.
S-8540/8541Cxx 255 300 345
kHz
Maximum duty ratio MaxDuty Measure waveform at the EXT pin. 100
−
−
%
2
PWM/PFM-control switch
duty ratio
*2
PFMDuty V
IN
= V
OUT (S)
×
1.5, no load 19 29 39
%
2
Current limit detection
voltage
V
SENSE
V
IN
= V
OUT (S)
×
1.5,
Measure waveform at the EXT pin.
100 125 150 mV 1
SENSE pin input current I
SENSE
V
IN
= V
OUT (S)
×
1.5, V
SENSE
= V
IN
−
0.1 V 6.7 11.2 16.8
μ
A 1
V
SH
V
IN
= V
OUT (S)
×
1.5, Judge V
OUT(S)
×
0.98. 2.3
−
−
V 2 Shutdown pin
input voltage
V
SL
V
IN
= V
OUT (S)
×
1.5, Judge CVREF pin "L".
−
−
0.3 V 1
I
SH
V
IN
= V
OUT (S)
×
1.5, V
ON/OFF
= V
OUT
−
0.1
−
0.1
μ
A 1 Shutdown pin
input leakage current
I
SL
V
IN
= V
OUT (S)
×
1.5, V
ON/OFF
= 0 V
−
0.1
−
0.1
μ
A 1
Soft-start time t
SS
Time until V
OUT (E)
reaches 90% or higher of the V
OUT(S)
7.0 12.0 17.0 ms 2
Efficiency EFFI
−
−
90
−
%
2
External components
Coil (L) :Sumida Corporation. CDRH6D28-100
Diode (SD) :
Matsushita Electric Inducstrial Co., Ltd.
MA2Q737 (Schottky diode)
Output capacitor (C
OUT
) :Nichicon Corporation F93 (16 V, 47 μF, tantalum)
Input capacitor (C
IN
) :Nichicon Corporation F93 (16 V, 47 μF, tantalum)
Transistor (P
SW
) :Toshiba Corporation 2SA1213
Base resistor (R
b
) :100 mΩ
Base capacitor (C
b
) :2200 pF
C
VL
:1.0 μF
C
SS
:0.047 μF
R
SS
:220 kΩ
R
SENSE
:100 mΩ
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
Caution 1. Line regulation and load regulation may change greatly due to GND wiring when V
IN
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.
