October 17, 2007

Low current (3 A) and high reliability achieved for automotive use
SPF7302 IC for Driving DC Motor Developed
Ideal for opening and closing swirl/tumble valves of direct fuel injection engines

Sanken Electric Co., Ltd. announces the development of the SPF7302 IC (package: surface-mount, 16 pins, withstand voltage: 36 V, current: 3 A) for driving DC motors that open and close swirl/tumble valves used in automobile direct fuel injection engines.  Sample shipments will begin on November 5th.  Shipments in volume will be available in January of next year, with a mass production of 5k units/month, then ramping up to 50k units/month at the end of CY09.  The sample price will be 800 yen (tax excluded).
   
1. Development Background and Product Overview
  Various direct fuel injection engines (*1) have been developed to lower fuel consumption of automobiles.  In direct fuel injection engines, gasoline is injected directly into the cylinder.  At this time, the flow of vaporized gasoline is controlled by generating air currents called swirl currents and tumble currents (*2) in the cylinder so that the vapor homogenously and properly spreads in the cylinder.  One of the mechanisms to generate such currents adopts a method that opens and closes a valve for control and a DC motor is used for driving the valve.

Although such DC motors operate with a current as low as about 1A which is their rated current, there have been almost no driver ICs with an appropriate output current for automotive application, so larger ICs (5 A to 6 A) for throttle valves have been used as alternatives.

Thus, Sanken has developed the SPF7302 IC for driving DC motors.  The IC employs a full-bridge configuration circuit required for driving DC motors, the rated current is 3 A, and a low-loss, low on-resistance power elements (MOSFETs) are incorporated in one chip which is encapsulated in a compact surface mount package.

To secure strict reliability for automotive use, the SPF7302 builds in various protection and auxiliary functions which work as protection of IC itself as well as protection on the load side, including an overvoltage detection and a function for detecting open output pins that have been adopted for the first time for ICs for driving motors in this class, as well as overheat protection, undervoltage protection and a two-step overcurrent protection circuit.

The SPF7302, ensuring high reliability for automotive use, is an ideal IC for other low-current automotive applications (such as door mirror position adjustment and in-vehicle TV operation, etc.) other than swirl/tumble valves.

(*1) Conventional engines: Gasoline and air are mixed in the suction pipe in advance and injected into the cylinder for burning.
Direct fuel injection engines: Both air and gasoline are directly injected into the cylinder, where they are mixed and burned. An opening and closing valve is used for in-taking such air.

(*2) Currents that are generated using swirl/tumble valves so that air and gasoline are homogenously mixed in the cylinder in a direct fuel injection engine
- Swirl (horizontal) current: Air current that flows along the circumference in the cylinder
- Tumble (vertical) current: Air current that vertically circulates in the cylinder
 
2. Features
 
(1) Adopts a compact surface mount package with higher heat dissipation
Adopts a compact surface mount package with higher heat dissipation, having thermal resistance: 3.2° C/W (between junction and case)
(Dimensions of resin part: 12 × 7.5 × 2.5 mm, Sanken name: SPF16Pin)

(2) Low on-resistance MOSFETs in one chip
Low-loss, low on-resistance (on-resistance: 150 mΩ , typ.) MOSFETs (four transistors) are built into one chip as power elements.  The high-side elements are driven by the charge pump circuit method.

(3) Built-in overcurrent protection circuit operating in two steps for each power element
- Current-limit function operating at 3 A (The current-limit operates only for the MOSFET(s) exceeding 3 A, with current-limit release function)
- Protection function operating at 6 A (All the MOSFETs are turned off when 6 A is exceeded at short circuit load, etc. A signal is output upon activation.)

(4) Detection of open output pins and signal output upon detection
Improves system reliability by detecting the disconnection of motor and wiring, and by outputting a signal

(5) Controls the operation by two input signals
By applying the signals to two pins, the IC controls changeover between normal rotation,reverse rotation and break operation of the DC motor.

(6) Versatile built-in protections and auxiliary functions
- Undervoltage protection, outputting a signal upon activation
- Overheat protection, outputting a signal upon activation
- Overvoltage detection, outputting a signal upon activation

   
3. Specifications
 
Parameter Ratings Unit Remark
Main power supply voltage -0.3 to 36 V  
Output current ±3 A  
±6(pulse) 1kHz, Duty<1%, Pulse<10μs
Power dissipation 39 W When infinite heat sink is used
Output MOSFET on-resistance 300(max) Io=1A
Junction temperature -40 to +150 ° C  
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