SI-8008TM
Description
The SI-8008TM DC voltage regulator is a DC-to-DC buck
convertor that attains an oscillation frequency of 300 kHz,
and has an integrated miniaturized choke coil, allowing it to
serve as a small, high efficiency power supply in a compact
TO252-5 (SC-63) package.
The switching regulator function realizes a high efficiency
switching regulator operation without adjustment, requiring
only six external support components, and an optional capacitor
for soft start operation and an optional transistor for on/off
control. The SI-8008TM includes overcurrent and overheating
protection circuits.
Applications include:
▪ DVD recorder
▪ FPD TV
▪ Telecommunications equipment
▪ Office automation equipment, such as printers
▪ On-board local power supply
▪ Output voltage regulator for second stage of SMPS
(switched mode power supply)
Features and Benefits
▪ 1.5 A output current supplied in a small power surface
mount package
▪ High efficiency: 81% at VIN
= 15 V, IO
= 0.5 A,VO
= 5 V
▪ Requires only six external components (optional soft
start requires an additional capacitor)
▪ Oscillation circuit built-in (frequency 300 kHz typical
▪ Constant current type overcurrent protection circuit and
an overheating protection circuit built in
▪ Soft start function built-in (can be implemented as an
ON/OFF function, output OFF state at low level)
▪ Low consumption current during output OFF state
DC-to-DC Step-Down Converter
Functional Block Diagram with Typical Application
Package: TO252-5 (SC-63)
Not to scale
PReg
Latch
&
Driver
Overcurrent
Protection
Thermal
Protection
Reference
Voltage
ON/
OFF
Soft
Start
Oscillator
Reset
Comparator
Error Amp
VIN 1
5
3
4
2VO
L
Di C2
C1
C3
SI -8008TM
SS
GND
ADJ
SW
IN
R1
R2
Component Rating
C1 220 μF
C2 470 μF
C3 1 μF (for soft start function)
Di SJPB-H6 (Sanken)
L1 47 μH
Figure 1. Application implementing soft start, without implementation of on/off control.
27469.054
DC-to-DC Step-Down Converter
SI-8008TM
2
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, TA, of 25°C, unless oth er wise stated.
Absolute Maximum Ratings
Characteristic Symbol Remarks Rating Units
DC Input Voltage VIN 43 V
Power Dissipation 1 PD1
Glass-epoxy board mounting in 900 mm2, copper area 4.3%,
Tj ≤ 125°C 1.06 W
Power Dissipation 2 PD2
Glass-epoxy board mounting in 900 mm2, copper area 50%
Tj ≤ 125°C 1.65 W
Junction Temperature TJ
The thermal protection circuit is built-in and may enable when
junction temperature rises to 130°C or higher. Recommended
maximum junction temperature during product operation is 125°C.
–30 to 150 °C
Storage Temperature Tstg –40 to 150 °C
Thermal Resistance (Junction-case) Rθj-c 6 °C/W
Thermal Resistance (Junction-ambient air) Rθj-a Glass-epoxy board mounting in 900 mm2, copper area 4.3% 95 °C/W
Selection Guide
Part Number Output Voltage
(V) Efficiency (Typical)
(%) Input Voltage
(V) Output Current
(A) Packing
SI-8008TM-TL
(Adjustable Type) 0.8 (VADJ)81
(5 V Set-up) 43 0 to 1.5 3000 pieces per reel
Recommended Operating Conditions
Characteristic Symbol Remarks Min. Max. Units
DC Input Voltage Range1VIN IO = 0 to 1.5 A VO + 3 40 V
DC Output Voltage Range VO0.8 24 V
DC Output Current Range2IOVIN ≥ VO + 3 V 0 1.5 A
Operating Junction Temperature Range TJOP –20 100 °C
Operating Temperature Range2TOP –20 85 °C
1The minimum value of the input voltage, VIN (min) is the larger of either 4.5 V or VO+3 V. In the case in which VIN is in the range VO + 2 V to VO + 3 V,
VIN(min) is set so that IO = 1 A (maximum).
2To be used within the allowable package power dissipation characteristics (refer to Power Dissipation chart).
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
3
SI-8008TM
(a)
V
O
on/off
control only
(c)
V
O
on/off and
soft start control
(b)
Soft start
only
C3
SS
5
SI-8008TM
SS
5
SI-8008TM
SS
5
System
TTL
C3
System
TTL
ELECTRICAL CHARACTERISTICS, valid at TA = 25°C, VO = 5 V (adjusted), R1 = 4.2 kΩ, R1 = 0.8 kΩ
Characteristic Symbol Test Conditions Min. Typ. Max. Units
Reference Voltage VADJ VIN = 15 V, IO = 0.1 A 0.784 0.8 0.816 V
Reference Voltage Temperature Coefficient ∆VREF
/∆TV
IN = 15 V, IO = 0.1 A, TOP = 0 to 100 °C – ±0.1 – mV/°C
Efficiency* ηVIN = 15 V, IO = 0.5 A – 81 – %
Operating Frequency fOVIN = 15 V, IO = 0.5 A – 300 – kHz
Line Regulation VLine VIN = 10 to 30 V, IO = 0.5 A – 60 80 mV
Load Regulation VLoad VIN = 15 V, IO = 0.2 to 1.5 A – 10 40 mV
Overcurrent Protection Threshold Current ISVIN = 15 V 1.6 – – A
SS Terminal On/Off Operation Threshold Voltage VSSL – – 0.5 V
SS Terminal On/Off Operation Outflow Current ISSL VSSL = 0 V – 10 40 μA
Quiescent Current 1 IqVIN = 15 V, IO = 0 A – 6 – mA
Quiescent Current 2 Iq(off) VIN = 15 V, VSS = 0 V – 200 400 μA
*Efficiency is calculated by the following equation.
100
V
O IO
η (%) =
V
IN IIN
Terminal List Table
Name Number Function
IN 1 Supply voltage
SW 2 Regulated supply output
GND 3 Ground terminal
ADJ 4 Terminal for resistor bridge feedback
SS 5
The SS terminal is used to enable soft start and to control on/off operation of the IC output,
VO (see figure 2). To enable soft start, connect a capacitor between SS and ground. To
control on/off operation, connect an NPN bipolar transistor, in a TTL open collector output
configuration, between the SS terminal and GND. Turn off is done by decreasing VSSL
below its rated level.
When both soft start and VO on/off are used, a protection measure such as current limiting
is required because, if the capacitance of C3 large, the discharge current of C3 flows
across the transistor for on/off operation. Because a pull-up type resistor is provided inside
the IC, no external voltage can be applied.
Pin-out Diagram
Figure 2. Alternative configurations for SS pin. If neither soft start nor VO on/off is required, the SS pin is left open.
12345
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
4
SI-8008TM Performance Characteristics at TA = 25°C
85
80
75
70
65
60
55
0 0.5 1 1.5
I
O
(A)
η(%)
5.06
5.04
5.02
5.00
4.98
4.96
4.94
4.92
4.90
4.88
4.86
4.84 00.2
0.4 0.6 0.8 1.0 1.2 1.4 1.6
V
O
(V)
0
100
200
300
400
0 10203040
6
5
4
3
2
1
0
0246810
Efficiency versus
Output Current
V
O
= 5 V (Adjusted)
R
1
= 4.2 kΩ
R
2
= 0.8 kΩ
Circuit Current at
Output Off versus
Supply Voltage
V
SS
= 0 V
Load
Regulation:
Output Voltage
versus
Output Current
Low Voltage
Behavior
Output Voltage
versus
Supply Voltage
8V 10 V15 V
40 V
30 V
20 V
I
O(0ff)
(μA)
V
IN
(V)
0
2
4
8
6
10
0 10203040
Quiescent Current
versus
Supply Voltage
I
O
= 0 A
I
q
(mA)
V
IN
(V)
V
O
(V)
V
IN
(V)
I
O
(A)
VIN
VIN
8V
10 V
15 V
40 V
30 V
20 V
0 A
0.1 A
0.5 A
1.0 A
1.5 A
IO
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
5
SI-8008TM Thermal Performance Characteristics
0
0.5
1.0
1.5
10 100 1000
6
5
4
3
2
1
0
0 20 40 60 80 100 120 140 180160
T
J
(°C)
V
O
(V)
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
–25 0 25 50 75 100 125
Thermal Protection: Output Voltage
versus Junction Temperature
V
IN
= 8 V, I
O
= 0.01 A
Junction temperature, T
J
, can be calculated as:
where R
θJC
= 6°C/W, and T
C
is the temperature
taken by a thermocouple mounted adjacent
to the case on the tab at the location indicated:
Device Thermal Resistance versus
Exposed Copper Area on PCB
Glass-epoxy PCB, 30 mm
2
Device Power Dissipation versus
Exposed Copper Area on PCB
Glass-epoxy PCB, 30 mm
2
Power Dissipation
versus Ambient Temperature
T
J
(max) = 125°C
Mounted on glass-epoxy PCB (30 mm
×
30 mm),
with varying exposed copper areas
TSD On
P
D
(W)
T
A
(°C)
Copper Area (mm
2
)
Copper Area (mm
2
)
TSD Off
Cu Area: 625 mm
2
R
θJA
= 58.9°C/W
Cu Area: 450 mm
2
R
θJA
= 60.4°C/W
Cu Area: 270 mm
2
R
θJA
= 65.1°C/W
Cu Area: 180 mm
2
R
θJA
= 71.4°C/W
Cu Area: 90 mm
2
R
θJA
= 80.3°C/W
Cu Area: 39 mm
2
R
θJA
= 93.7°C/W
where:
V
O
is output voltage in V,
V
IN
is input supply voltage in V,
I
O
is output current in A,
η
X
is IC efficiency in percent (varies with V
IN
and I
O
; refer to
efficiency curve for value), and
V
F
is forward voltage for the input diode, D
i
. In these tests,
the Sanken SJPB-H6 was used, at 0.5 V and I
O
= 1.5 A.
For application design, obtain thermal data from the
datasheet for the diode.
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−⋅−
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛−⋅=
IN
O
OF
x
OOD
V
V
IVIVP 11
100
H
TJ = PD × RθJC + TC
T
A
25°C
40°C
60°C
85°C
40
50
60
70
80
90
100
10 100 1000
Thermocouple mount
at tab center
RθJA(°C/W)PD(W)
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
6
Component Selection
VIN
1
GND GND
2
4
53
GND
SS
IN SW
ADJ
C1
220 μF
C2
470 μF
L 47 μH
Di
VO
SI-8008TM
R1
R2
IADJ
C3
Component Rating
C1 220 μF
C2 470 μF
C3 1 μF (for soft start function)
Di SJPB-H6 (Sanken)
L1 47 μH
Diode Di
A Schottky-barrier diode must be used for Di. If other diode types
are used, such as fast recovery diodes, the IC may be destroyed
because of the reverse voltage applied by the recovery voltage or
ON voltage.
Choke Coil L1
If the winding resistance of the choke coil is too high, the
efficiency may go down to the extent that it is out of the rating.
Because the overcurrent protection start current is approximately
2.5 A, attention must be paid to the heating of the choke coil by
the magnetic saturation due to overload or short-circulated load.
Capacitor C1,C2, and C3
As large ripple currents flow across C1 and C2, capacitors with
high frequency and low impedance for SMPS must be used.
Especially when the impedance of C2 is high, the switching
waveform may not be normal at low temperature. Please use
neither OS capacitors nor tantalum capacitors which cause an
abnormal oscillation for C2.
C3 is a capacitor for soft start. In case soft start function is not
used, please keep the SS terminal open. A pull-up resistor is pro-
vided inside the IC.
Resistor R1 and R2
R1, R2 is a resistor bridge to the output voltage. IADJ should be
set to 1 mA. To do so, calculate R1, R2 by the following expres-
sions:
()()
),
(()
Ω
×
===Ω
×
−
=
−
=
−−
k
I
V
R
V
IVV
R
ADJ
ADJO
ADJ
ADJO
8.0
101
8.0
2
101
8.0
1
33
R2 should always be connected for stable operation, even if out-
put voltage, VO, is set to 0.8 V. It is recommended that VO be set
at VIN+ 8% or greater.
8008TM
C1 C2
C3
Di
IN
R2
R1
SW
Vo
GND
L
++
All external components should be mounted as close as possible
to the SI-8008TM. The ground of all components should be
connected at one point.
Recommended PCB Layout Recommended Solder Pad Layout
Typical Application Circuit
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
7
0.5 ±0.10
2.3 ±0.20
0.5 ±0.10
0.5 ±0.10
Terminal dimension at lead tips
(5×)
1.524 +0.254
–0.127
(0.89)
Seating Plane
0.00–0.127
(1.00)
0-8°
6.10 ±0.20
2.70 ±0.20
Branding
0.70 MAX
XXXXXXXX
XXXXXXXX
Terminal core material: Cu
Terminal treatment: Ni plating and solder dip
Heat sink core material: Cu
Heat sink treatment: Ni plating
Approximate weight: 0.33 g
Dimensions in millimeters
Branding codes (exact appearance at manufacturer discretion):
1st line, type: 8008TM
2nd line, lot: YM W
Where: Y is the last digit of the year of manufacture
M is the month (1 to 9, O, N, D)
W is the week
3rd line, Tracking number (four digits)
12 34 5
4×P1.27 TYP
5.34 ±0.20
6.60 ±0.20
R0.25
1.10 ±0.2
9.90 ±0.30
(4.41)
(1.50)
(5.04)
+ +
0.01
5X
PACKAGE OUTLINE DRAWING, TO252-5
Device is lead (Pb) free.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
8
PACKING SPECIFICATION
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
9
WARNING — These devices are designed to be operated at lethal voltages and energy levels. Circuit designs
that embody these components must conform with applicable safety requirements. Pre cau tions must be
taken to prevent accidental contact with power-line potentials. Do not connect ground ed test equipment.
The use of an isolation transformer is recommended during circuit development and breadboarding.
Because reliability can be affected adversely by improper storage
environments and handling methods, please observe the following
cautions.
Cautions for Storage
• Ensure that storage conditions comply with the standard
temperature (5°C to 35°C) and the standard relative humidity
(around 40 to 75%); avoid storage locations that experience
extreme changes in temperature or humidity.
• Avoid locations where dust or harmful gases are present and
avoid direct sunlight.
• Reinspect for rust on leads and solderability of products that have
been stored for a long time.
Cautions for Testing and Handling
When tests are carried out during inspection testing and other
standard test periods, protect the products from power surges
from the testing device, shorts between adjacent products, and
shorts to the heatsink.
Soldering
• When soldering the products, please be sure to minimize the
working time, within the following limits:
260±5°C 10 s
350±5°C 3 s
• Soldering iron should be at a distance of at least 1.5 mm from the
body of the products
Electrostatic Discharge
• When handling the products, operator must be grounded.
Grounded wrist straps worn should have at least 1 MΩ of
resistance to ground to prevent shock hazard.
• Workbenches where the products are handled should be
grounded and be provided with conductive table and floor mats.
• When using measuring equipment such as a curve tracer, the
equipment should be grounded.
• When soldering the products, the head of soldering irons or the
solder bath must be grounded in other to prevent leak voltages
generated by them from being applied to the products.
• The products should always be stored and transported in our
shipping containers or conductive containers, or be wrapped in
aluminum foil.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
DC-to-DC Step-Down Converter
SI-8008TM
10
The products described herein are manufactured in Ja pan by Sanken Electric Co., Ltd. for sale by Allegro MicroSystems, Inc.
Sanken and Allegro reserve the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be re quired to per mit im-
prove ments in the per for mance, reliability, or manufacturability of its prod ucts. Therefore, the user is cau tioned to verify that the in for ma tion in this
publication is current before placing any order.
When using the products described herein, the ap pli ca bil i ty and suit abil i ty of such products for the intended purpose shall be reviewed at the users
responsibility.
Although Sanken undertakes to enhance the quality and reliability of its prod ucts, the occurrence of failure and defect of semi con duc tor products
at a certain rate is in ev i ta ble.
Users of Sanken products are requested to take, at their own risk, preventative measures including safety design of the equipment or systems
against any possible injury, death, fires or damages to society due to device failure or malfunction.
Sanken products listed in this publication are designed and intended for use as components in general-purpose electronic equip ment or apparatus
(home ap pli anc es, office equipment, tele com mu ni ca tion equipment, measuring equipment, etc.). Their use in any application requiring radiation
hardness assurance (e.g., aero space equipment) is not supported.
When considering the use of Sanken products in ap pli ca tions where higher reliability is re quired (transportation equipment and its control systems
or equip ment, fire- or burglar-alarm systems, various safety devices, etc.), contact a company sales representative to discuss and obtain written
confirmation of your spec i fi ca tions.
The use of Sanken products without the written consent of Sanken in applications where ex treme ly high reliability is required (aerospace equip-
ment, nuclear power-control stations, life-support systems, etc.) is strictly prohibited.
The information in clud ed herein is believed to be accurate and reliable. Ap pli ca tion and operation examples described in this pub li ca tion are
given for reference only and Sanken and Allegro assume no re spon si bil i ty for any in fringe ment of in dus tri al property rights, intellectual property
rights, or any other rights of Sanken or Allegro or any third party that may result from its use.
Copyright © 2007 Allegro MicroSystems, Inc.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
