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TC428EPA 数据表(PDF) 3 Page - TelCom Semiconductor, Inc |
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TC428EPA 数据表(HTML) 3 Page - TelCom Semiconductor, Inc |
3 / 5 page 4-171 TELCOM SEMICONDUCTOR, INC. 7 6 5 4 3 1 2 8 TC426 TC427 TC428 1.5A DUAL HIGH-SPEED POWER MOSFET DRIVERS *Static-sensitive device. Unused devices must be stored in conductive material. Protect devices from static discharge and static fields. Stresses above those listed under "Absolute Maximum Ratings" may cause perma- nent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions above those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may effect device reliability. SUPPLY BYPASSING Charging and discharging large capacitive loads quickly requires large currents. For example, charging a 1000-pF load to18V in 25nsec requires an 0.72A current from the device power supply. To guarantee low supply impedance over a wide fre- quency range, a parallel capacitor combination is recom- mended for supply bypassing. Low-inductance ceramic disk capacitors with short lead lengths (< 0.5 in.) should be used. A 1 µF film capacitor in parallel with one or two 0.1 µF ceramic disk capacitors normally provides adequate bypassing. GROUNDING The TC426 and TC428 contain inverting drivers. Ground potential drops developed in common ground impedances from input to output will appear as negative feedback and degrade switching speed characteristics. Individual ground returns for the input and output circuits or a ground plane should be used. INPUT STAGE The input voltage level changes the no-load or quies- cent supply current. The N-channel MOSFET input stage transistor drives a 2.5mA current source load. With a logic "1" input, the maximum quiescent supply current is 8 mA. Logic "0" input level signals reduce quiescent current to 0.4 mA maximum. Minimum power dissipation occurs for logic "0" inputs for the TC426/427/428. Unused driver inputs must be connected to VDD or GND. The drivers are designed with 100 mV of hysteresis. This provides clean transitions and minimizes output stage current spiking when changing states. Input voltage thresh- olds are approximately 1.5V, making the device TTL com- patible over the 4.5V to 18V supply operating range. Input current is less than 1 µA over this range. The TC426/427/428 may be directly driven by the TL494, SG1526/1527, SG1524, SE5560, and similar switch- mode power supply integrated circuits. POWER DISSIPATION The supply current vs frequency and supply current vs capacitive load characteristic curves will aid in determining power dissipation calculations. The TC426/427/428 CMOS drivers have greatly re- duced quiescent DC power consumption. Maximum quies- cent current is 8 mA compared to the DS0026 40 mA specification. For a 15V supply, power dissipation is typi- cally 40 mW. Two other power dissipation components are: • Output stage AC and DC load power. • Transition state power. Output stage power is: Po = PDC + PAC = Vo (IDC) + f CL VS Where: Vo = DC output voltage IDC = DC output load current f = Switching frequency Vs = Supply voltage In power MOSFET drive applications the PDC term is negligible. MOSFET power transistors are high imped- ance, capacitive input devices. In applications where resis- tive loads or relays are driven, the PDC component will normally dominate. The magnitude of PAC is readily estimated for several cases: A. B. 1. f = 20kHZ 1. f = 200kHz 2. CL =1000pf 2. CL =1000pf 3. Vs = 18V 3. VS =15V 4. PAC = 65mW 4. PAC = 45mW During output level state changes, a current surge will flow through the series connected N and P channel output MOSFETS as one device is turning "ON" while the other is turning "OFF". The current spike flows only during output transitions. The input levels should not be maintained be- tween the logic "0" and logic "1" levels. Unused driver inputs must be tied to ground and not be allowed to float. Average power dissipation will be reduced by mini- mizing input rise times. As shown in the characteristic curves, average supply current is frequency dependent. |
类似零件编号 - TC428EPA |
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类似说明 - TC428EPA |
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