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SI-8005Q Step-Down Switching Regulator with Current-Mode Control
Features and Benefits
Current-mode control system employed Excellent line regulation (60 mV maximum) 165 m 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 VREF of 0.5 V. High efficiency, 94% maximum at VIN = 8 V, VO = 5 V, and IO = 0.5 A Operating frequency 500 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-8005Q 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 HSOP8 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-8005Q are reduced by controlling the maximum on-resistance of a built-in output MOSFET to as low as 165 m. Furthermore, die miniaturization has been accomplished through a proprietary BCD process. The SI-8005Q 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-8005Q 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: HSOP8 surface mount with exposed thermal pad
Not to scale
Functional Block Diagram
27469.058
SI-8005Q
Selection Guide
Part Number SI8005Q-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
VIN VEN PD TJ Tstg RJA RJC
Remarks
Rating
30 6
Unit
V V W C C C/W C/W
Limited by internal thermal shutdown, mounted on a 30 mm x 30 mm glass epoxy PCB with 25 mm x 25 mm exposed copper area, TJ(max) = 125C Internal thermal shutdown activates at approximately 140C Mounted on a 30 mm x 30 mm glass epoxy PCB with 25 mm x 25 mm exposed copper area
1.35 -30 to 150 -40 to 150 74 40
Recommended Operating Conditions*
Characteristic DC Input Voltage Range DC Output Current Range Operating Junction Temperature Range Operating Temperature Range Symbol VIN IO TJOP TOP Operation within PD limits Remarks VIN(min) is the greater of either 4.75 V or VO+1 V; except if VO + 0.5 VIN VO +1 V, then VIN(min) is set such that IO 2 A Using the circuit defined in the Typical Application diagram and within PD 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.
Maximum Allowable Package Power Dissipation
1.6 1.4 Power Dissipation, PD (W) 1.2 1.0 0.8 0.6 0.4 0.2 0 -25 0 25 50 75 Ambient Temperature, TA (C) 100 125
Results calculated as:
100 PD = VO x IO x - 1 - VF x IO
where: VO is the output voltage,
VO 1 - VIN
VIN is the Input voltage (0.4 V for these results), IO is the Output current (0.3 A for these results), x is the efficiency (%), which varies with VIN and IO (derived from the Efficiency curves in the Characteristic Performance section), and VF 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 SJPB-D4 was used for these results).
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 25C, unless otherwise stated.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
2
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
ELECTRICAL CHARACTERISTICS1, valid at TA=25C, unless otherwise noted Characteristics Reference Voltage Output Voltage Temperature Coefficient Efficiency2 Operating Frequency Line Regulation Load Regulation Overcurrent Protection Threshold Quiescent Current 1 Quiescent Current 2 SS Terminal Leakage Current3 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
1Using
Symbol VREF VREF/T fO VLINE VLOAD IS IIN IIN(off) ISSL VCEH VCEL ICEH AEA GEA 1/GCS DCMAX tMIN
Conditions VIN = 12 V, IO = 1.0 A VIN = 12 V, IO = 1.0 A, TA = -40C to 85C VIN = 12 V, VO = 5 V, IO = 1 A VIN = 16 V, VO = 5 V, IO = 1 A VIN = 8 to 28 V, VO = 5 V, IO = 1 A VIN = 12 V, VO = 5 V, IO = 0.1 to 3.5 A VIN = 12 V, VO = 5 V VIN = 12 V, VO = 5 V, IO = 0 A, VEN = open VIN = 12 V, VO = 5 V, IO = 0 A,VEN = 0 V VSSL = 0 V, VIN = 16 V VIN = 12 V VIN = 12 V VEN = 0 V
Min 0.485 - - 450 - - 3.6 - - - 2.8 - - - - - - -
Typ 0.500 0.05 90 500 10 10 - 18 - 5 - - 1 1000 800 0.35 92 100
Max 0.515 - - 550 60 60 6.0 - 20 - - 2.0 - - - - - -
Units V mV/C % kHz mV mV A mA A A V V A V/ V A/V V/A % ns
circuit shown in Measurement Circuit diagram. 2Efficiency is calculated as: (%) = ([V x I ] x [V x I ]) x 100. O O IN IN 3SS 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
2 7 EN C1
IIN IEN
1 IN BS S I- 8005Q 5 FB GND 4 COM P 6 C3 3 SW
C4 L1
Component
R1 C2
Rating 22 F / 50 V 47 F / 25 V 220 pF / 10 V 10 nF / 25 V SPB-G56S 10 H 46 k 5.1 k 62 k
8
SS
Di
IO
ISS
VFB
R2
VO
RL
VIN
VEN
VSS
R3
C1 C2 C3 C4 Di L1 R1 R2 R3
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
3
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
Performance Characteristics
at TA = 25C
100 90 80
100
8V VIN 4.75 V 5V
90 80
12 V
Efficiency versus Output Current VO = 1.2 V
70 60 50 40
8V 12 V
6V
Efficiency versus Output Current VO = 3.3 V
70 60 50 40
16 V 24 V 28 V VIN
(%)
0
1
2
3
4
5
(%)
0
1
2
3
4
5
IO (A)
100 90
IO (A)
100
8V
12 V
90
16 V 20 V
16 V
80
20 V VIN
(%)
80
Efficiency versus Output Current VO = 5 V
(%)
28 V
70 60 50 40
Efficiency versus Output Current VO = 12 V
28 V
70 60 50 40
VIN
0
1
2
3
4
5
0
1
2
3
4
5
IO (A)
IO (A)
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
4
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
Performance Characteristics
at TA = 25C
6 5 4 VO (V) 6
0A 1A 2A
5 4
20 V 24 V 28 V
8V 12 V 15 V
Overcurrent Protection Load = CR
3 2 1 0
Overcurrent Protection
IO
VO (V)
3A
3 2 1 0 VIN
0
2
4
6
8
10
0
1
2
3
4
5
6
VIN (V)
5.05 5.04 5.03 5.02 VO (V) 25
IO (A)
VIN
IO(Q) (mA)
20
Load Regulation
5.01 5.00 4.99 4.98 4.97 4.96 4.95 0 1
28 V 20 V 15 V
8V
12 V
Quiescent Current versus Input Voltage IO = 0 A
15
10
5
2
3
4
5
0
0
10
20
30
40
IO (A)
10 9 8 7 IO(Q) (A) 5 4 6
VIN (V)
OTP On
Quiescent Current versus Input Voltage VEN = 0 V
VO (V)
6 5 4 3 2 1 0 0 10 20 30 40
Overvoltage Protection VIN = 12 V IO = 0 A
3 2 1
OTP Off
0 120 550 130 140 TJ (C) 150 160
VIN (V)
550 540 530 520 540
8V 12 V 15 V
VIN
530 520
fO (kHz)
490 480 470 460 450 0 1
fO (kHz)
Operating Frequency versus Output Current
510 500
Operating Frequency versus Input Voltage
20 V 24 V 28 V
510 500 490 480 470 460
2
3
4
5
450
0
10
20
30
40
IO (A)
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
VIN (V)
5
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
Component Selection
Diode Di A Schottky-barrier diode must be used for Di. If other diode types, such as like fast recovery diodes, are used, the IC may be destroyed because of reverse voltages applied by the recovery voltage or turn-on voltage. Choke Coil L1 If the winding resistance of the choke coil is too high, IC efficiency may go down to the extent that the resistance is beyond the rating. Because the overcurrent protection threshold current is approximately 4 A, attention must be paid to the heating of the choke coil by magnetic saturation due to overload or short-circulated load. Capacitors C1, C2, and C5 Because large ripple currents for SMPS flow across C1 and C2, capacitors with high frequency and low impedance must be used. Especially when the impedance of C2 is high, the switching waveform may not be normal at low temperatures.
C5 is used to enable soft start. If the soft start function is not used, leave the SS terminal open. Resistors R1 and R2 R1 and R2 set the output voltage, VO. Select the resistor values to set IADJ to 0.1 mA. R1 and R2 are calculated by the following expression:
R1 =
(VO - VFB ) = (VO - 0.5)( )R 2 =
I ADJ 0.1x 10 -3
0.5 VFB = 5k ( ) I ADJ 0.1x 10 -3
For optimum performance, minimize the distance between components. Phase Compensation Components C3, C6, and R3 The stability and response of the loop is controlled through the COMP pin. The COMP pin is the output of the internal transconductance
Typical Application Diagram
VIN C4 L1 SW 3 R1 FB COM P 6 C3 C6 O P EN R3 G ND G ND 4 VFB 5 Di R2 IA D J C2 VO 5V
2 IN 7 EN
1 BS
Component C1 (2 ea) C2 (2 ea) C3 C4, C5 Di L1 R1 R2 R3
Rating 10 F / 50 V 22 F / 16 V 220 pF 10 nF 10 H 46 k 5.1 k 62 k
Manufacturer Murata, P/N GRM55DB31H106KA87 Murata, P/N GRM32ER71A226KE20 Murata, P/N GRM18 series Murata, P/N GRM18 series Sanken, P/N SPB-G56S or SJPB-L4
S I- 8005Q
C1 8 SS
C5
G ND
Recommended PCB Layout
R3 FB C6 COMP C3 EN SS C5 GND U1 C1 Vin C4 Vout Vsw D1 L1 C2 R2 R1
Recommended Solder Pad Layout
U ni : m m t 4.30 1.35
0.54 1.27
2.80
All external components should be mounted as closely as possible to the SI-8005Q. The ground of all components should be connected at one point. The exposed copper area on the PCB that is connected to the heat sink on the reverse side of package is ground. Enlarging the PCB copper area enhances thermal dissipation from the package.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
3.00
6
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
amplifier. The combination of a series-connected capacitor and resistor sets the combination of a pole and zero frequency point that decide the characteristics of the control system. The DC gain of the voltage feedback loop is calculated by the following equation:
Adc = Rl x Gcs x AEA x
where VFB is the feedback voltage (0.5 V), AEA is the error amplifier voltage gain,
VFB , Vout
(1)
The goal of phase compensation design is to shape the converter transfer function to get the required loop gain. The system crossover frequency, where the feedback loop has unity gain, is important. Lower crossover frequencies result in slower line and load transient responses. On the other hand, higher crossover frequencies cause system instability. A good standard is to adjust the crossover frequency to approximately one-tenth of the switching frequency. The optimal selection of phase compensation components can be determined using the following procedure: 1. Choose the phase compensation resistor (R3) to adjust the required crossover frequency. R3 value is calculated by the following equation:
GCS is the current sense transconductance, and Rl is the load resistor value. The system has two important poles. One is set by the phase compensation capacitor (C3) and the output resistor of the error amplifier. The other is set by the output capacitor and load resistor. These poles are calculated by the following equations:
R3 =
2 x C 2 x fc Vout 2 x C 2 x 0.1x fs Vout x < x , (7) GEA x GCS VFB GEA x GCS VFB
fp1 = fp 2 =
GEA 2 x C 3 x AEA , 1 2 x C 2 x Rl ,
(2) (3)
where fc is the required crossover frequency. This is usually adjusted to less than one-tenth of the switching frequency. 2. Choose the phase compensation capacitor (C3) to get the required phase margin. For applications that have typical inductor values, adjusting the compensation zero point to less than onequarter of crossover frequency provides sufficient phase margin. The value of C3 is calculated by the following equation:
where GEA is the error amplifier transconductance. The system has one important zero point. This is set by the phase compensation capacitor (C3) and phase compensation resistor (R3). The zero point is shown by the following equation:
C3 >
1 fz1 = 2 x C 3 x R3 .
4 2 x R3 x fc ,
(8)
(4)
where R3 is the phase compensation resistor. 3. It is necessary to determine whether a second compensation capacitor (C6) is required. It is required if the ESR zero point of the output capacitor is less than half of the switching frequency, expressed as follows:
If the value of the output capacitor is the large or if it has a high ESR, the system may have another important zero point. This zero point would be set by the ESR and capacitance of the output capacitor. The zero point is shown by the following equation:
fESR =
1 2 x C 2 x RESR .
(5)
In this case a third pole, which is set by the phase compensation capacitor (C6) and phase compensation resistor (R3), is used to compensate the effect of the ESR zero point on the loop gain. The pole is shown by the following equation:
1 fs < 2 x C 2 x RESR 2.
(9)
If this is the case, add the second compensation capacitor (C6) and adjust ESR zero frequency (fp3). C6 value is calculated by the following equation:
fp 3 =
1 2 x C 6 x R3 .
(6)
C6 =
C 2 x RESR . R3
(10)
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
7
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
Package Outline Drawing
8 5.20 0.15 Branding area
Tracking number in dimple
4.40
6.20
0.40
1
2
0.695 TYP 0.40 1.27 2.90
1.50 0.08 0.08 0.05 0.05
Dimensions in millimeters Branding codes (exact appearance at manufacturer discretion): 1st line, type: 8005Q 2nd line, lot: SK YMDD Where: Y is the last digit of the year of manufacture M is the month (1 to 9, O, N, D) DD is the date 3rd line, control : NNNN
Leadframe plating Pb-free. Device composition complies with the RoHS directive.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
2.70
8
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
Packing Specification
Empty tape Trailer IC occupied tape Empty Tape Leader
Cover Tape
Units More than 160mm More than 400mm Direction of reel 1.55
mm
160mm
1,000pcs (1,000 pockets)
4
2
8
5.5 12
5.6 7
(4.75)
2
Void 60
Void 60
B
13 0.2
Void 60 180
Void
3 R22 Void Void
10 13 0.3 15.4 0.1
Void
Void
Center extension
2 5 4 10.5 13 5 11.9 3 R22
10
30
60
3
60
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
9
SI-8005Q
Step-Down Switching Regulator with Current-Mode Control
Cautions
In general, the junction temperature level of surface mount package ICs is dependent upon the area and material of the PC board and its copper area. Therefore, please design the PCB to allow sufficient margin for heat dissipation. Parallel Operation Parallel operation of multiple products to increase the current is not allowed. Thermal Shutdown The SI-8000Q series has a thermal protection circuit. This circuit keeps the IC from the damage by overload. But this circuit cannot guarantee the long-term reliability against the continuous overload conditions. ESD Susceptibility Take precautions against damage by static electricity.
The products described herein are manufactured in Japan by Sanken Electric Co., Ltd. for sale by Allegro MicroSystems, Inc. Sanken and Allegro reserve the right to make, from time to time, such departures from the detail specifications as may be required to permit improvements in the performance, reliability, or manufacturability of its products. Therefore, the user is cautioned to verify that the information in this publication is current before placing any order. When using the products described herein, the applicability and suitability 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 products, the occurrence of failure and defect of semiconductor products at a certain rate is inevitable. 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 equipment or apparatus (home appliances, office equipment, telecommunication equipment, measuring equipment, etc.). Their use in any application requiring radiation hardness assurance (e.g., aerospace equipment) is not supported. When considering the use of Sanken products in applications where higher reliability is required (transportation equipment and its control systems or equipment, fire- or burglar-alarm systems, various safety devices, etc.), contact a company sales representative to discuss and obtain written confirmation of your specifications. The use of Sanken products without the written consent of Sanken in applications where extremely high reliability is required (aerospace equipment, nuclear power-control stations, life-support systems, etc.) is strictly prohibited. The information included herein is believed to be accurate and reliable. Application and operation examples described in this publication are given for reference only and Sanken and Allegro assume no responsibility for any infringement of industrial property rights, intellectual property rights, or any other rights of Sanken or Allegro or any third party that may result from its use.
Copyright (c) 2007 Allegro MicroSystems, Inc.
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com
10
Step-Down Switching Regulator with Current-Mode Control
SI-8005Q

January, 2008
Asia Pacific
China
Sanken Electric Hong Kong Co., Ltd. Suite 1026 Ocean Centre, Canton Road, Tsimshatsui, Kowloon, Hong Kong Tel: 852-2735-5262 Fax: 852-2735-5494 Sanken Electric (Shanghai) Co., Ltd. Room3202, Maxdo Centre, Xingyi Road 8, Changning district, Shanghai, China Tel: 86-21-5208-1177 Fax: 86-21-5208-1757 Taiwan Sanken Electric Co., Ltd. Room 1801, 18th Floor, 88 Jung Shiau East Road, Sec. 2, Taipei 100, Taiwan R.O.C. Tel: 886-2-2356-8161 Fax: 886-2-2356-8261
India
Saket Devices Pvt. Ltd. Office No.13, First Floor, Bandal - Dhankude Plaza, Near PMT Depot, Paud Road, Kothrud, Pune - 411 038, India Tel: 91-20-5621-2340 91-20-2528-5449 Fax: 91-20-2528-5459
Japan
Sanken Electric Co., Ltd. Overseas Sales Headquaters Metropolitan Plaza Bldg. 1-11-1 Nishi-Ikebukuro, Toshima-ku, Tokyo 171-0021, Japan Tel: 81-3-3986-6164 Fax: 81-3-3986-8637
Korea
Sanken Electric Korea Co., Ltd. Mirae Asset Life Bldg. 6F, 168 Kongduk-dong, Mapo-ku, Seoul, 121-705, Korea Tel: 82-2-714-3700 Fax: 82-2-3272-2145
Singapore
Sanken Electric Singapore Pte. Ltd. 150 Beach Road, #14-03 The Gateway West, Singapore 189720 Tel: 65-6291-4755 Fax: 65-6297-1744
Sanken Electric Co., Ltd.
I02-010EA-080130
Step-Down Switching Regulator with Current-Mode Control
SI-8005Q
Europe
United Kingdom
Sanken Power Systems (UK) Limited Pencoed Technology Park Pencoed, Bridgend CF35 5HY. UK Tel: 44-1656-869-100 Fax: 44-1656-869-162
January, 2008
North America
United States
Allegro MicroSystems, Inc. 115 Northeast Cutoff, Worcester, Massachusetts 01606, U.S.A. Tel: 1-508-853-5000 Fax: 1-508-853-3353 Allegro MicroSystems, Inc. (Southern California) 14 Hughes Street, Suite B105, Irvine, CA 92618 Tel: 1-949-460-2003 Fax: 1-949-460-7837
Sanken Electric Co., Ltd.
I02-010EA-080130

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