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| PD - 91746C IRF7805/IRF7805A HEXFET(R) Chip-Set for DC-DC Converters * * * * N Channel Application Specific MOSFETs Ideal for Mobile DC-DC Converters Low Conduction Losses Low Switching Losses S S S G 1 8 7 A D D D D 2 3 6 Description These new devices employ advanced HEXFET Power MOSFET technology to achieve an unprecedented balance of on-resistance and gate charge. The reduced conduction and switching losses make them ideal for high efficiency DC-DC Converters that power the latest generation of mobile microprocessors. The IRF7805/IRF7805A offers maximum efficiency for mobile CPU core DC-DC converters. 4 5 SO-8 T o p V ie w Device Features IRF7805 IRF7805A Vds 30V 30V Rds(on) 11m 11m Qg 31nC 31nC Qsw 11.5nC Qoss 36nC 36nC Absolute Maximum Ratings Parameter Drain-Source Voltage Gate-Source Voltage Continuous Drain or Source Current (VGS 4.5V) Pulsed Drain Current Power Dissipation 25C 70C Junction & Storage Temperature Range Continuous Source Current (Body Diode) Pulsed source Current TJ, TSTG IS ISM 2.5 106 25C 70C IDM PD Symbol VDS VGS ID 13 10 100 2.5 1.6 -55 to 150 2.5 106 C A IRF7805 30 12 13 10 100 W A IRF7805A Units V Thermal Resistance Parameter Maximum Junction-to-Ambient RJA Max. 50 Units C/W www.irf.com 1 10/10/00 IRF7805/IRF7805A Electrical Characteristics Parameter Drain-to-Source Breakdown Voltage* Static Drain-Source on Resistance* Drain-Source Leakage Current* V(BR)DSS RDS(on) 1.0 30 150 IGSS Qg Q gs1 Q gs2 Qgd QSW Q oss Rg td(on) tr td (off) tf 100 22 31 3.7 1.4 6.8 8.2 30 1.7 16 20 38 16 11.5 36 IRF7805 Min Typ Max 30 - 9.2 - 11 1.0 30 150 100 22 31 3.7 1.4 6.8 8.2 30 1.7 16 20 38 16 ns 36 VDD = 16V ID = 7A Rg = 2 VGS = 4.5V Resistive Load Conditions IS = 7A, VGS = 0V di/dt = 700A/s VDS = 16V, VGS = 0V, IS = 7A di/dt = 700A/s (with 10BQ040) VDS = 16V, VGS = 0V, IS = 7A VDS = 16V, VGS = 0 nC nA IRF7805A Min Typ Max Units 30 - 9.2 - 11 V m V A Conditions VGS = 0V, ID = 250A VGS = 4.5V, ID = 7A VDS = VGS,ID = 250A VDS = 24V, VGS = 0 VDS = 24V, VGS = 0, Tj = 100C VGS = 12V VGS = 5V, ID = 7A VDS = 16V, ID = 7A Gate Threshold Voltage* VGS(th) IDSS Gate-Source Leakage Current* Total Gate Charge* Pre-Vth Gate-Source Charge Post-Vth Gate-Source Charge Gate to Drain Charge Switch Charge* (Qgs2 + Qgd) Output Charge* Gate Resistance Turn-on Delay Time Rise Time Turn-off Delay Time Fall Time Source-Drain Rating & Characteristics Parameter Diode Forward Voltage* Reverse Recovery Charge Reverse Recovery Charge (with Parallel Schotkky) Notes: * Min VSD Qrr Qrr(s) Typ Max 1.2 88 55 Min Typ Max Units 1.2 88 55 V nC 2 Repetitive rating; pulse width limited by max. junction temperature. Pulse width 300 s; duty cycle 2%. When mounted on 1 inch square copper board, t < 10 sec. Measured at VDS < 100mV. This approximates actual operation of a synchronous rectifier. Typ = measured - Qoss Devices are 100% tested to these parameters. www.irf.com IRF7805/IRF7805A Power MOSFET Selection for DC/DC Converters Control FET Special attention has been given to the power losses in the switching elements of the circuit - Q1 and Q2. Power losses in the high side switch Q1, also called the Control FET, are impacted by the Rds(on) of the MOSFET, but these conduction losses are only about one half of the total losses. Power losses in the control switch Q1 are given by; 4 Drain Current 1 Gate Voltage t2 VGTH t0 t1 t3 QGS1 QGS2 2 QGD Ploss = Pconduction+ Pswitching+ Pdrive+ Poutput This can be expanded and approximated by; Drain Voltage Figure 1: Typical MOSFET switching waveform Ploss = (Irms 2 x Rds(on) ) Q + I x gd x Vin x ig + (Qg x Vg x f ) Q + oss x Vin x f 2 This simplified loss equation includes the terms Qgs2 and Qoss which are new to Power MOSFET data sheets. Qgs2 is a sub element of traditional gate-source charge that is included in all MOSFET data sheets. The importance of splitting this gate-source charge into two sub elements, Qgs1 and Qgs2, can be seen from Fig 1. Qgs2 indicates the charge that must be supplied by the gate driver between the time that the threshold voltage has been reached (t1) and the time the drain current rises to Idmax (t2) at which time the drain voltage begins to change. Minimizing Qgs2 is a critical factor in reducing switching losses in Q1. Qoss is the charge that must be supplied to the output capacitance of the MOSFET during every switching cycle. Figure 2 shows how Qoss is formed by the parallel combination of the voltage dependant (non-linear) capacitance's Cds and Cdg when multiplied by the power supply input buss voltage. Synchronous FET Q f + I x gs2 x Vin x ig f The power loss equation for Q2 is approximated by; * Ploss = Pconduction + Pdrive + Poutput Ploss = Irms x Rds(on) + (Qg x Vg x f ) ( 2 ) Q Q + oss x Vin x f + ( rr x Vin x f ) 2 *dissipated primarily in Q1. www.irf.com 3 IRF7805/IRF7805A For the synchronous MOSFET Q2, Rds(on) is an important characteristic; however, once again the importance of gate charge must not be overlooked since it impacts three critical areas. Under light load the MOSFET must still be turned on and off by the control IC so the gate drive losses become much more significant. Secondly, the output charge Qoss and reverse recovery charge Qrr both generate losses that are transfered to Q1 and increase the dissipation in that device. Thirdly, gate charge will impact the MOSFETs' susceptibility to Cdv/dt turn on. The drain of Q2 is connected to the switching node of the converter and therefore sees transitions between ground and Vin. As Q1 turns on and off there is a rate of change of drain voltage dV/dt which is capacitively coupled to the gate of Q2 and can induce a voltage spike on the gate that is sufficient to turn the MOSFET on, resulting in shoot-through current . The ratio of Qgd/Qgs1 must be minimized to reduce the potential for Cdv/dt turn on. Spice model for IRF7805 can be downloaded in machine readable format at www.irf.com. Figure 2: Qoss Characteristic 4 www.irf.com IRF7805/IRF7805A Typical Characteristics IRF7805 IRF7805A Figure 3. Normalized On-Resistance vs. Temperature Figure 4. Normalized On-Resistance vs. Temperature Figure 5. Typical Gate Charge vs. Gate-to-Source Voltage Figure 6. Typical Gate Charge vs. Gate-to-Source Voltage Figure 7. Typical Rds(on) vs. Gate-to-Source Voltage Figure 8. Typical Rds(on) vs. Gate-to-Source Voltage www.irf.com 5 IRF7805/IRF7805A IRF7805 10 10 IRF7805A ISD , Reverse Drain Current (A) TJ = 150 C ISD , Reverse Drain Current (A) TJ = 150 C 1 1 TJ = 25 C TJ = 25 C 0.1 0.4 V GS = 0 V 0.5 0.6 0.7 0.8 0.9 0.1 0.4 V GS = 0 V 0.5 0.6 0.7 0.8 0.9 VSD ,Source-to-Drain Voltage (V) VSD ,Source-to-Drain Voltage (V) Figure 9. Typical Source-Drain Diode Forward Voltage Figure 10. Typical Source-Drain Diode Forward Voltage 100 Thermal Response (Z thJA ) D = 0.50 0.20 0.10 0.05 0.02 0.01 SINGLE PULSE (THERMAL RESPONSE) P DM t1 t2 Notes: 1. Duty factor D = t 1 / t 2 2. Peak T J = P DM x Z thJA + TA 0.01 0.1 1 10 100 1000 10 1 0.1 0.001 t1 , Rectangular Pulse Duration (sec) Figure 11. Maximum Effective Transient Thermal Impedance, Junction-to-Ambient 6 www.irf.com IRF7805/IRF7805A Package Outline SO-8 Outline Part Marking Information SO-8 www.irf.com 7 IRF7805/IRF7805A Tape & Reel Information SO-8 Dimensions are shown in millimeters (inches) T E R M IN A L N U M B E R 1 1 2.3 ( .4 84 ) 1 1.7 ( .4 61 ) 8 .1 ( .31 8 ) 7 .9 ( .31 2 ) F E E D D IR E C T IO N N O TE S : 1 . C O N T R O L L IN G D IM E N S IO N : M IL L IM E T E R . 2 . A L L D IM E N S IO N S A R E S H O W N IN M IL L IM E T E R S (IN C H E S ). 3 . O U T L IN E C O N F O R M S T O E IA -4 8 1 & E IA -5 4 1 . 33 0.0 0 (12 .9 92 ) MAX. 14 .4 0 ( .5 6 6 ) 12 .4 0 ( .4 8 8 ) NOTE S : 1 . C O N T R O L LIN G D IM E N S IO N : M IL L IM E T E R . 2 . O U T L IN E C O N FO R M S T O E IA -48 1 & E IA -54 1. IR WORLD HEADQUARTERS: 233 Kansas St., El Segundo, California 90245, USA Tel: (310) 252-7105 IR EUROPEAN REGIONAL CENTRE: 439/445 Godstone Rd, Whyteleafe, Surrey CR3 OBL, UK Tel: ++ 44 (0)20 8645 8000 IR CANADA: 15 Lincoln Court, Brampton, Ontario L6T3Z2, Tel: (905) 453 2200 IR GERMANY: Saalburgstrasse 157, 61350 Bad Homburg Tel: ++ 49 (0) 6172 96590 IR ITALY: Via Liguria 49, 10071 Borgaro, Torino Tel: ++ 39 011 451 0111 IR JAPAN: K&H Bldg., 2F, 30-4 Nishi-Ikebukuro 3-Chome, Toshima-Ku, Tokyo 171 Tel: 81 (0)3 3983 0086 IR SOUTHEAST ASIA: 1 Kim Seng Promenade, Great World City West Tower, 13-11, Singapore 237994 Tel: ++ 65 (0)838 4630 IR TAIWAN:16 Fl. Suite D. 207, Sec. 2, Tun Haw South Road, Taipei, 10673 Tel: 886-(0)2 2377 9936 Data and specifications subject to change without notice. 10/00 8 www.irf.com |
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