Electronic Components Datasheet Search |
|
CPC1580PTR Datasheet(PDF) 9 Page - Clare, Inc. |
|
CPC1580PTR Datasheet(HTML) 9 Page - Clare, Inc. |
9 / 11 page CPC1580 R00G www.clare.com 9 5. Application Switching Losses During the transition intervals, the application and load components change energy states and, in the process, incur switching losses. The switching losses are manifested as heat in the application circuit and must be addressed by the designer to ensure that no one component exceeds its power rating. The designer must understand the details of the load behavior in order to adequately size and protect the application circuit. There are three general cases to observe: (1) purely resistive loads, (2) inductive/resistive loads, and (3) loads with significant capacitance. Inductors and capacitors are energy storage elements that require special consideration for switching. During the switching periods, energy is conserved. Inductors turning off transfer their stored energy to MOSFET switching losses, to the capacitance of the load and application circuit, and to the protector. During the turn-on interval, the inductor energy is zero, and so the capacitive energy in the load and parasitic elements of the switching application must be dissipated by the MOSFET, in order for the load to change state. To calculate the stored inductive energy in Joules: 5.1 Resistive Load Losses: The Ideal Case For purely resistive loads, the energy dissipated by changing states occurs primarily in the MOSFET. The equation describing MOSFET energy dissipation during rise time, in Joules, is: The average power of the MOSFET for any load type in Watts is: Where fSWITCH is the application switching frequency; RDSAT is the MOSFET’s on-resistance; D is the switch's operational duty cycle: D = tON/(tON+tOFF); and EFALL is MOSFET energy dissipation during fall time, in Joules. 5.2 Inductive/Resistive Loads If the load is resistive and inductive, and the inductance doesn't saturate, the load current during turn off, tRISE, in Amps is: and the MOSFET drain voltage during turn off, tRISE, in Volts is: The instantaneous power in the MOSFET will be the product of the two equations and the energy will be the integral of the power over time. 5.3 Capacitive Loads The energy absorbed by the MOSFET for loads that are more capacitive in nature occurs during the MOSFET turn-on as opposed to the turn-off. The energy absorbed by the MOSFET will be a function of the load, the TVS (or other protector), and the MOSFET drain capacitance. The MOSFET energy, EFALL, in Joules is: COSS is the MOSFET output capacitance found in the data sheet. As mentioned earlier, the MOSFET switching losses occur at different times, either rising or falling, so loads with a combination of inductance and capacitance can also be calculated by the energy equations described above. 5.4 dV/dt Characteristics The application circuit shown in Figure 1 dissipates significant energy caused by large dV/dt events. Fault voltages across the MOSFET will turn it on for the same reason the part turns off slowly. For dV/dt events > IG_SINK/CRSS (from Equation 2) the application circuit will dissipate energy proportional to the CRSS and gFS (forward conductance) of the selected transistor. CRSS is a function of the transistor's on-resistance and current/power capability, so higher load designs are more sensitive. The CPC1580 provides an internal clamp to protect the gate of the MOSFET from damage in such an event. The part can withstand 100mA for short periods, like dV/dt transients. EL = • L • ILOAD 2 1 2 ERISE > VLOAD 2 IG_SINK CRSS ILOAD 6 • = PLOAD 6 • tRISE • PAVG = ILOAD 2 •• • RDSAT D + fSWITCH (ERISE + EFALL) ILOAD(t) = VLOAD RLOAD IG_SINK LLOAD • CRSS - () • RLOAD LLOAD • t - 1 + e -R LOAD LLOAD •t 2 RLOAD LLOAD ] [• VDRAIN(t) = IG_SINK CRSS • t EFALL = 1 2 •(CTVS + COSS + CLOAD)• VLOAD 2 |
Similar Part No. - CPC1580PTR |
|
Similar Description - CPC1580PTR |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List 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 |