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CS452 датащи(PDF) 4 Page - Cherry Semiconductor Corporation |
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CS452 датащи(HTML) 4 Page - Cherry Semiconductor Corporation |
4 / 5 page 4 The CS452/453 is provided with an input lead (VIN) which turns the injector driver ÓonÒ and ÓoffÒ. This lead has a nominal trip level of 1.4V and an input impedance of 20k½. It is internally protected against negative voltages and is compatible with TTL and most other logic. There is also a control lead (CONTROL) which if held low or grounded, permits the device to operate in saturation to Ipk(sense), where it will switch to Isus automatically. If CON- TROL is brought high (>1.5V), the output drive stage is turned off, regardless of what state the input (VIN) is at, and the output current goes to zero. Figure 1 shows the operating waveforms for the simplest mode; i.e., with CONTROL grounded. When the driver is turned on, the current ramps up to the peak current sense level, where some overshoot occurs because of internal delay. The CS452/453 then reduces its output to Isus. The fall time of the device is very rapid (²1.0µs), but the decay of the load current takes 150 to 220 µs, while dumping the load energy into the protection Zener clamp. It is essential that the Zener voltage be lower than the V(BR)CEO(sus), but not so low as to greatly stretch the load current decay time. Without the zener, the discharge of the load energy would be totally into the CS452/453, which, for the high current applications, could cause the device to fail. Also in figure 1 is the graphically derived instantaneous power dissipation of the CS452/453. It shows that, for practical purposes, the worst case dissipation is less than (Isus) (VBAT) (duty cycle). Figure 2. Switching Waveforms (Expanded Time Scale) Figure3. Switching Speed vs. Temperature 1.5 140 120 100 80 60 40 20 0 -20 -40 2.0 1.0 0.5 0 Case Temperature (ûC) ts tf tv 0 90% 1.0 2.0 3.0 ms Ipk 10% 0 Vl Turn Off Output Voltage Output Current ts tv tf Figure 4. Application of CONTROL Provided in Figures 2,3, and 4 are definitions of the switching intervals specified in the Electrical Characteristics. Figure 3 shows that the critical switching parameters stay under control at elevated temperatures. In those applications where high voltage transients may occur while the output lead (OUT) is in the Isus mode, excessive instantaneous power dissipation may occur, causing device failure. When this condition occurs, the control lead (CONTROL) can be used to shut off the out- put stage in order to protect the CS452/453. As long as CONTROL is in the high state (>1.5 volts, typ.), the output will remain off. One method of sensing the supply voltage and controlling CONTROL is to use a resistor divider between the supply voltage and ground with CONTROL connected to the resistor divider (see Typical Application diagram). Another application option of the control lead is to use it to accomplish an enable/disable function. Since CON- TROL is compatible with TTL and CMOS logic levels, a logic low will enable the output, and allow it to follow the input signal at VIN. If CONTROL is held at a logic high, the output will be disabled regardless of the state of the input signal. If the control function is not being used in the application, it must be grounded or otherwise placed in a logic low state. If CONTROL is left open, the output stage will remain off. The output current in the Isus mode should be oscillation free. There is a possibility that in a given application, the output current could oscillate for a small fraction of parts. If this was to occur, the remedy is place a capacitor from OUT to Ground. The value of the capacitor should not exceed 0.01µF. >1.4V >1.5V Ipk Isus Input Signal VIN Control Signal CONTROL Output Current tl Application Information |
Аналогичный номер детали - CS452 |
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Аналогичное описание - CS452 |
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