STK730C [SANYO]
5 V Single Output MOS Chopper Regulator; 5 V单路输出MOS斩波稳压器
| 型号： | STK730C |
| 厂家： | 
SANYO SEMICON DEVICE |
| 描述： | 5 V Single Output MOS Chopper Regulator |
| 文件： | 总6页 (文件大小：120K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
Ordering number : EN4472A
Thick Film Hybrid IC
STK730C
5 V Single Output MOS Chopper Regulator
Overview
Features
The STK730C is a chopper type step-down dedicated
5 V single output regulator that uses a power MOSFET
as its switching element and a Schottky barrier diode
(SBD) as its flywheel diode.
• IMST substrate (insulated metal substrate technology)
• Efficiency improved (by 10%) by the adoption of
MOSFET and SBD technology.
• An auxiliary drive power supply is no longer required
due to the development of a unique NMOS FET drive
circuit. This means that the STK730C can be used
with a single power supply, thus allowing
simplification of the input system.
The STK730C covers the 2 A and higher current
regions, regions that are difficult to handle with three
terminal step-down regulators. As compared with earlier
chopper regulator products that used bipolar transistors,
the efficiency of the STK730C has been further
improved by the adoption of MOSFET and SBD
technologies, and use of the STK730C enables further
miniaturization and increased performance in the end
product since it corresponds to the adoption of a
dedicated switching controller IC. Furthermore, due to
the development of a unique MOS drive circuit, the
STK730C can be used with a single power supply input.
• Built-in reverse going linear overload characteristic
curve overcurrent protection circuit
• Ground line handling is eased even in multi-output
power supply structures due to placement of the
overcurrent detection resistor on the plus line.
• The STK730C’s separate excitation oscillator
structure provides high stability in the switching
frequency.
• The STK730C’s switching operating frequency is set
at 125 kHz, which minimizes beating when used in a
multiple output structure with STK731 and STK733
type products.
The STK730C can prove useful when standardizing and
rationalizing power supply circuit design, since it can
handle a wide range of power supply circuits in a
number of applications, either as the secondary side
regulator in a switching power supply or as the output
regulator following AC transformer rectification.
Package Dimensions
unit: mm
4141
Applications
[STK730C]
• Power supplies in printers and other office equipment
• Power supplies in robots and other factory automation
related equipment
• Power supplies in VCRs and other consumer products
• Secondary side regulators in switching power supplies
SANYO Electric Co.,Ltd. Semiconductor Bussiness Headquarters
TOKYO OFFICE Tokyo Bldg., 1-10, 1 Chome, Ueno, Taito-ku, TOKYO, 110 JAPAN
73096HA (OT)/82793YO 5-2862 No. 4472-1/6
STK730C
Specifications
Maximum Ratings at Ta = 25°C
Parameter
Maximum DC input voltage
Maximum output current
Thermal resistance
Symbol
Rating
Unit
V
Vin (DC) max
40
5
I
max
A
O
θj-c
3.5 (SBD 7.2)
150 (SBD 125)
105
°C/W
°C
Junction temperature
Tj max
Tc max
Operating case temperature
Storage temperature
°C
T
–30 to +105
°C
stg
Electrical Characteristics at Ta = 25°C, for the specified test circuit
Rating
typ
Parameter
Symbol
Condition
Unit
min
4.95
max
5.15
Output voltage setting
V
O
5.05
V
mVrms
mV/V
mV/A
A
Vin (DC) = 24 V, I = 1 A
O
Ripple voltage
V
10
10
30
rp
Input regulation
Reg-IN
Reg-L
Vin (DC) = 10 to 40 V, I = 1 A
O
Load regulation
Vin (DC) = 24 V, I = 0.5 to 5 A
O
Overcurrent protection start current
Efficiency
I
Vin (DC) = 24 V
5
ocp
η
Vin (DC) = 24 V, I = 2.5 A
O
80
125
%
Operating frequency
Output voltage temperature coefficient
f
kHz
Vin (DC) = 24 V, I = 1 A
O
T
0.02
%/°C
cvo
Block Diagram
No. 4472-2/6
STK730C
Test Circuit
C1:
C2:
C3:
220 µF/50 V
1000 µF/10 V
1 µF/10 V
L1:
Rs1:
200 µH (HP-054/TOKIN)
0.05 Ω
Notes: • Do not use pin 7 or pin 9 as an intermediary for any other line or pin.
• Since pin 5 is grounded to the substrate, the noise level and other characteristics can be adversely affected if the heat sink is connected to the FG
or GND lines. If this is a problem either make the heat sink floating or use an insulating sheet.
STK730C Characteristics
Input variation characteristics
Load variation characteristics
Input voltage – V
Output current – A
Temperature characteristics
Substrate temperature – °C
No. 4472-3/6
STK730C
Thermal Design
The power dissipating sections of a power supply block consist of the power transistor (PTR), the flywheel diode
(FWD), the choke coil, and the current detection resistor. Of these, the components that are incorporated in the hybrid IC
itself are the PTR and the FWD.
Taking PT to be the power dissipated in the PTR and PF to be the power dissipated in the FWD, the power dissipation
Pd for the whole hybrid IC and the heat sink thermal resistance θc-a can be expressed as follows.
Pd = (PT + PF)
(W)
Tc – Ta
θc-a =
(°C/W)
Pd
Tc: Substrate temperature (105°C, maximum)
Ta: IC ambient temperature
The junction temperature, Tj, of each element can be expressed as follows.
Tj = PD × θj-c + Tc
(°C)
PD: Power loss for each element (PT, PF)
θj-c: The junction/case thermal resistance of each element
Thermal design consists of deriving the heat sink thermal resistance θc-a that satisfies the two thermal conditions, i.e.,
the maximum IC substrate temperature Tc max (105°C) and the maximum junction temperature Tj max for each
semiconductor device, and then implementing that thermal resistance. Since thermal dissipation is greatly influenced by
the ambient temperature, the structure of the equipment itself, and other factors, ample margins must be included in the
thermal design to take them into account.
The figure below left shows the relationship between area and thermal resistance when an aluminum plate is used in the
thermal design. The radiation characteristics of an aluminum plate can be improved by painting the surface black. This
can reduce the thermal resistance by 20% for a given surface area.
θc-a – S
IC power dissipation
Heat sink area, S – cm2
Output current, IO – A
IC power dissipation
IC power dissipation
Output current, IO – A
Output current, IO – A
No. 4472-4/6
STK730C
STK730C θj-c, Tj max
θj-c
Tj max
150°C
125°C
PTR (FET)
FWD (SBD)
3.5°C/W
7.2°C/W
Notes on PC Board Production
• Capacitor C1 should be placed as close as possible to the pin 10 input in the layout. (This is to prevent voltage drops in
the input lines and pattern. Also, a separate smoothing capacitor is required if the input is a direct current input using
rectified and smoothed AC.)
• Capacitor C2 should be placed as close as possible to the load in the layout. (This is to compensate for voltage drops
due to load fluctuations.)
• Pins 2 and 5 are voltage sensing lines, and should be connected close to the load, i.e., close to C2. (This is to
compensate for voltage drops in the pattern.)
• Pins 3 and 4 should be directly connected to the two terminals of the current detection resistor Rs1. (This is to prevent
detection based on pattern resistances.)
• Pin 6 should be connected to the capacitor C1 ground using a thick, short line to reduce the related loop area. (This is
to reduce switching spikes.)
• Power lines, i.e., lines that carry current, should be made as wide as possible in the pattern.
• When a ripple suppression LC filter is added, connect it at the location indicated by dotted lines in the figure. The
sensing line from pin 2 should be connected to the same position (the C2 location) as it is when no filter is used.
• The NC pins (pins 7 and 9) should not be connected to any other lines, even on the PC board.
Two Output Power Supply Structural Example (connecting to an STK733)
➀
➁
Note: It is possible for STK730 input ripple currents to cause L1 to vibrate audibly and adversely influence the 24 V system. If such problems occur, an
inductor can be inserted at the point marked with dotted lines in the figure to form an LC filter.
No. 4472-5/6
STK730C
Overvoltage Protection Circuit Recommendations
When constant voltage power supply circuits fail, or a problem such as poor soldering on the PC board appears, the
failure mode can involve an overvoltage state in which the output voltage becomes higher than the specified voltage.
When an overvoltage failure occurs, the load driven by the power supply is often damaged, and severe damage can
occur. Also, if the overvoltage exceeds the output capacitor’s voltage limitation, the capacitor’s internal electrolytic fluid
can be vaporized and released by the operation of the capacitor’s explosion prevention valve. This gas can appear to be
white smoke.
When designing a power supply circuit, the need for an overvoltage protection circuit is the same regardless of whether
discreet components or integrated circuits are used. We strongly recommend the use of an overvoltage protection circuit
to hold to a minimum any damage that may result from an overvoltage state.
Overvoltage Protection Circuit Example
The crowbar circuit is a well known overvoltage protection circuit.
A Zener diode with a voltage 1 V to 2 V higher than the output voltage of the power supply is used as the diode ZD.
When the output voltage exceeds this value due to a malfunction or other cause, the Zener diode operates and the SCR
goes to the turn on short state since the SCR gate potential is pulled up. At this point the fuse at the input to the constant
voltage blows, completing the operation of the overvoltage protection circuit.
If the ambient temperature varies widely the crowbar circuit operating point can change due to the temperature
characteristics of both the Zener diode and the SCR’s cathode/gate voltage. As a result, the protection function may
operate even when the output voltage is normal. This circuit may also operate due to external noise.
Since, in general, the output voltage will be highest for the largest input and the smallest load, the operation and
effectiveness of the protection circuit must be confirmed in the actual mounted configuration of the end product.
Note: Step down chopper power supplies can generate an overvoltage on the output side equivalent to the input voltage
if there is an assembly error on the PC board or if the IC fails. Therefore we strongly recommend the use of a
crowbar or other overvoltage protection circuit in power supply designs.
■ No products described or contained herein are intended for use in surgical implants, life-support systems, aerospace
equipment, nuclear power control systems, vehicles, disaster/crime-prevention equipment and the like, the failure of
which may directly or indirectly cause injury, death or property loss.
■ Anyone purchasing any products described or contained herein for an above-mentioned use shall:
➀ Accept full responsibility and indemnify and defend SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and
distributors and all their officers and employees, jointly and severally, against any and all claims and litigation and all
damages, cost and expenses associated with such use:
➁ Not impose any responsibility for any fault or negligence which may be cited in any such claim or litigation on
SANYO ELECTRIC CO., LTD., its affiliates, subsidiaries and distributors or any of their officers and employees
jointly or severally.
■ Information (including circuit diagrams and circuit parameters) herein is for example only; it is not guaranteed for
volume production. SANYO believes information herein is accurate and reliable, but no guarantees are made or implied
regarding its use or any infringements of intellectual property rights or other rights of third parties.
This catalog provides information as of July, 1996. Specifications and information herein are subject to change
without notice.
No. 4472-6/6
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