Step-Down Switching Regulator with Current-Mode Control
Features and Benefits
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Current-mode control system employed
Excellent line regulation (60 mV maximum)
165 mΩ maximum on-resistance of built-in MOSFET
Output current 3.5 A
Wide range of input voltages (4.75 to 28 V), supports
24 V direct drive
Output voltage 0.5 to 24 V, compatible with various IC
power supply voltages, through low V
REF
of 0.5 V.
High efficiency, 94% maximum at V
IN
= 8 V, V
O
= 5 V,
and I
O
= 0.5 A
Operating frequency 350 kHz, supports downsizing of
smoothing choke coil
Soft start and output on/off functions built-in
Built-in protection:
▫
Drooping overcurrent protection
▫
Overtemperature protection
▫
Undervoltage lockout (UVLO)
Description
The SI-8105QL is a step-down switching regulator IC, designed
as an output voltage regulator at the secondary stage of switch
mode power supplies. The current-mode control system permits
small ceramic capacitors to be used as output capacitors.
Together with the compact DIP8 package, this allows reduction
of regulator circuitry area on the PCB by approximately 50%
in comparison with conventional topologies.
Designed to save power, losses in the SI-8105QL are reduced
by controlling the maximum on-resistance of a built-in output
MOSFET to as low as 165 mΩ. Furthermore, die miniaturization
has been accomplished through a proprietary BCD process.
The SI-8105QL supplies an output current of 3.5 A and an output
voltage that is variable from 0.5 to 24 V, which is easily set to
a voltage compatible with the diverse reduced power supply
voltages required by signal processing ICs. Accepting a wide
input voltage range, from 4.75 to 28 V, the SI-8105QL can be
driven directly by a 24 V power supply.
Applications include power supplies for signal processing ICs
for memories and microcomputers used in plasma display panel
(PDP) TVs, liquid crystal display (LCD) TVs, computer hard
drives, and DVD recorders.
Package: 8-pin DIP
Not to scale
Functional Block Diagram
27469.065, Rev. 1
SANKEN ELECTRIC CO., LTD.
http://www.sanken-ele.co.jp/en/
SI-8105QL
Selection Guide
Part Number
SI8105QL-TL
Step-Down Switching Regulator with Current-Mode Control
Packing
1000 pieces per reel
Absolute Maximum Ratings
Characteristic
DC Input Voltage
DC Input Voltage
Allowable Power Dissipation
Junction Temperature
Storage Temperature
Thermal Resistance (Junction to Ambient)
Thermal Resistance (Junction to Case)
Symbol
V
IN
V
EN
P
D
T
J
T
stg
R
θJA
R
θJC
Remarks
Rating
30
6
Unit
V
V
W
°C
°C
°C/W
°C/W
Limited by internal thermal shutdown, mounted on a 70 mm × 60 mm
glass epoxy PCB with 1310 mm
2
exposed copper area
Internal thermal shutdown activates at approximately 140°C
Mounted on a 70 mm × 60 mm glass epoxy PCB with 1310 mm
2
exposed copper area
1.50
–30 to 150
–40 to 150
67
25
Recommended Operating Conditions*
Characteristic
DC Input Voltage Range
DC Output Current Range
Operating Junction
Temperature Range
Operating Temperature
Range
Symbol
V
IN
I
O
T
JOP
T
OP
Operation within P
D
limits
Remarks
V
IN
(min) is the greater of either 4.75 V or V
O
+3 V; except
if V
O
+ 2
≤
V
IN
≤
V
O
+ 3 V, then V
IN
(min) is set such that
I
O
≤
2 A
Using the circuit defined in the Typical Application
diagram and within P
D
limits
Min.
See
remarks
0
–30
–30
Typ.
–
–
–
–
Max.
28
3.5
125
85
Units
V
A
°C
°C
*Recommended operating range indicates conditions which are required for maintaining normal circuit functions shown in the
Electrical Characteristics table.
27469.065, Rev. 1
SANKEN ELECTRIC CO., LTD.
2
[Date]
SI-8105QL
Step-Down Switching Regulator with Current-Mode Control
ELECTRICAL CHARACTERISTICS
1
, valid at T
A
=25°C, unless otherwise noted
Characteristics
Reference Voltage
Output Voltage Temperature
Coefficient
Efficiency
2
Operating Frequency
Line Regulation
Load Regulation
Overcurrent Protection Threshold
Quiescent Current 1
Quiescent Current 2
SS Terminal Leakage Current
3
EN Terminal High Level Voltage
EN Terminal Low Level Voltage
EN Terminal Leakage Current
Error Amplifier Voltage Gain
Error Amplifier Transconductance
Current Sense To COMP
Transimpedance
Maximum Duty Cycle (On)
Minimum On-Time
1
Using
2
Efficiency
Symbol
V
REF
∆V
REF
/∆T
η
f
O
V
LINE
V
LOAD
I
S
I
IN
I
IN(off)
I
SSL
V
CEH
V
CEL
I
CEH
A
EA
G
EA
1/G
CS
DC
MAX
t
MIN
Conditions
V
IN
= 12 V, I
O
= 1.0 A
V
IN
= 12 V, I
O
= 1.0 A, T
A
= –25°C to 100°C
V
IN
= 12 V, V
O
= 5 V, I
O
= 1 A
V
IN
= 16 V, V
O
= 5 V, I
O
= 1 A
V
IN
= 8 to 28 V, V
O
= 5 V, I
O
= 1 A
V
IN
= 12 V, V
O
= 5 V, I
O
= 0.1 to 3.5 A
V
IN
= 12 V, V
O
= 5 V
V
IN
= 12 V, V
O
= 5 V, I
O
= 0 A, V
EN
= open
V
IN
= 12 V, V
O
= 5 V, I
O
= 0 A,V
EN
= 0 V
V
SSL
= 0 V, V
IN
= 12 V
V
IN
= 12 V
V
IN
= 12 V
V
EN
= 0 V
Min
0.485
–
–
315
–
–
3.6
–
–
–
2.8
–
–
–
–
–
–
–
Typ
0.500
±0.05
90
350
20
20
–
18
–
5
–
–
1
1000
800
0.35
92
100
Max
0.515
–
–
385
50
50
6.0
–
20
–
–
2.0
–
–
–
–
–
–
Units
V
mV/°C
%
kHz
mV
mV
A
mA
μA
μA
V
V
μA
V/ V
μA/V
V/A
%
ns
circuit shown in Measurement Circuit diagram.
is calculated as:
η(%)
= ([V
O
×
I
O
] / [V
IN
×
I
IN
]) × 100.
3
SS terminal enables soft start when a an external capacitor is connected to it. Because a pull-up resistor is provided inside the IC, no external voltage
can be applied to this terminal.
Measurement Circuit Diagram
Component
2
7
EN
C1
I
IN
I
EN
Rating
10
μF
/ 50 V
47
μF
/ 25 V
1200 pF / 10 V
10 nF / 25 V
1000 pF
SPB-G56S
22
μH
46 kΩ
5.1 kΩ
20 kΩ
10
Ω
1
IN
BS
S I- 8105QL
5
FB
GND
4
COM P
6
C3
R3
C5
R4
3
SW
C4
L1
8
SS
Di
R1
C2
I
O
I
SS
V
FB
R2
V
O
RL
V
IN
V
EN
V
SS
C1
C2
C3
C4
C5
Di
L1
R1
R2
R3
R4
All performance characteristics given are typical values for circuit or
system baseline design only and are at the nominal operating voltage and
an ambient temperature, T
A
, of 25°C, unless otherwise stated.
27469.065, Rev. 1
SANKEN ELECTRIC CO., LTD.
3
[Date]
SI-8105QL
Step-Down Switching Regulator with Current-Mode Control
Maximum Allowable Package Power Dissipation
Mounted on a 70 mm × 60 mm glass epoxy PCB with
1310 mm
2
exposed copper area
Results calculated as:
1.6
1.4
Power Dissipation, P
D
(W)
1.2
1.0
0.8
0.6
0.4
0.2
0
–25
0
75
25
50
Ambient Temperature, T
A
(°C)
100
125
⎛
100
⎞
P
D
=
V
O
×
I
O
⎜
–
1
⎟
–
V
F
×
I
O
⎜
x
⎟
⎝
⎠
where:
V
O
is the output voltage,
⎛
V
O
⎞
⎜
1
–
⎟
⎜
V
IN
⎟
⎝
⎠
V
IN
is the Input voltage (0.4 V for these results),
I
O
is the Output current (0.3 A for these results),
ηx
is the efficiency (%), which varies with V
IN
and I
O
(derived from the
Efficiency curves in the Characteristic Performance section), and
V
F
is the diode forward voltage for D1, determination of the value for D1
should be made based on testing with the actual application (Sanken
diode SFPB-54 was used for these results).
Package Power Dissipation with No Load
I
O
= 0 A, L = 22
μH,
T
A
= 25°C
Power Dissipation (W)
Power Dissipation (W)
Package Power Dissipation with Load
L = 22
μH,
T
A
= 25°C
1.0
0.8
0.6
0.4
0.2
0
0
0.2
0.4
0.6 0.8 1.0 1.2
Output Current (A)
1.4
1.6
V
IN
= 12 V
V
O
= 6 V
V
IN
= 28 V
V
O
= 12 V
1.0
0.8
0.6
0.4
0.2
0
0
5
10
15
20
Output Voltage (V)
25
30
V
IN
= 12 V
V
IN
= 28 V
Note: When the SI-8105QL is operating in Discontinuous Conduction mode,
the SI-8105QL has internal losses because the SI-8105QL must dissipate
the energy from the charged Output capacitor (C2 in the Functional Block
diagram) through the low-side switch MOSFET (Q1) on the SW circuit.
27469.065, Rev. 1
SANKEN ELECTRIC CO., LTD.
4
[Date]
SI-8105QL
Step-Down Switching Regulator with Current-Mode Control
嵌入式系统
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