Moteur de recherche de fiches techniques de composants électroniques |
|
TC428MJA Fiches technique(PDF) 6 Page - Microchip Technology |
|
TC428MJA Fiches technique(HTML) 6 Page - Microchip Technology |
6 / 16 page TC426/TC427/TC428 DS21415C-page 6 © 2006 Microchip Technology Inc. 3.0 APPLICATIONS INFORMATION 3.1 Supply Bypassing Charging and discharging large capacitive loads quickly requires large currents. For example, charging a 1000 pF load to 18V in 25 nsec requires an 0.72A current from the device power supply. To ensure low supply impedance over a wide frequency 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. 3.2 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. 3.3 Input Stage The input voltage level changes the no-load or quiescent supply current. The N-channel MOSFET input stage transistor drives a 2.5 mA 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/TC427/TC428. 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 thresholds are approximately 1.5V, making the device TTL compatible over the 4.5V to 18V supply operating range. Input current is less than 1 μA over this range. The TC426/TC427/TC428 may be directly driven by the TL494, SG1526/1527, SG1524, SE5560, and similar switch-mode power supply integrated circuits. 3.4 Power Dissipation The supply current vs frequency and supply current vs capacitive load characteristic curves will aid in determining power dissipation calculations. The TC426/TC427/TC428 CMOS drivers have greatly reduced quiescent DC power consumption. Maximum quiescent current is 8 mA compared to the DS0026 40 mA specification. For a 15V supply, power dissipation is typically 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 2 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 resistive 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 = 200 kHZ 1. f = 200 kHz 2. CL =1000 pf 2. CL =1000 pf 3. Vs = 18V 3. Vs = 15V 4. PAC = 65 mW 4. PAC = 45 mW 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 between 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 minimizing input rise times. As shown in the characteristic curves, average supply current is frequency dependent. |
Numéro de pièce similaire - TC428MJA |
|
Description similaire - TC428MJA |
|
|
Lien URL |
Politique de confidentialité |
ALLDATASHEET.FR |
ALLDATASHEET vous a-t-il été utile ? [ DONATE ] |
À propos de Alldatasheet | Publicité | Contactez-nous | Politique de confidentialité | Echange de liens | Fabricants All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |