PD – 91746C IRF7805/IRF7805A HEXFET® Chip-Set for DC-DC Converters • • • • N Channel Application Specific MOSFETs Ideal for Mobile DC-DC Converters Low Conduction Losses Low Switching Losses 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. A D 1 8 S 2 7 D S 3 6 D G 4 5 D S SO-8 T o p V ie w Device Features IRF7805 IRF7805A Vds 30V 30V Rds(on) 11mΩ 11mΩ Qg 31nC 31nC Qsw 11.5nC Qoss 36nC 36nC Absolute Maximum Ratings Parameter Symbol Drain-Source Voltage Gate-Source Voltage 25°C Current (VGS ≥ 4.5V) 70°C Pulsed Drain Current 25°C ±12 13 13 10 10 IDM 100 100 2.5 PD W TJ, TSTG –55 to 150 °C IS 2.5 2.5 Pulsed source Current ISM 106 106 www.irf.com A 1.6 Continuous Source Current (Body Diode) Thermal Resistance Parameter Maximum Junction-to-Ambient Units V ID 70°C Junction & Storage Temperature Range IRF7805A 30 VGS Continuous Drain or Source Power Dissipation IRF7805 VDS RθJA Max. 50 A Units °C/W 1 10/10/00 IRF7805/IRF7805A Electrical Characteristics Parameter Drain-to-Source Breakdown Voltage* V(BR)DSS Static Drain-Source on Resistance* RDS(on) Gate Threshold Voltage* VGS(th) Drain-Source Leakage Current* IDSS Gate-Source Leakage Current* IGSS Total Gate Charge* IRF7805 Min Typ Max IRF7805A Min Typ Max Units 30 30 – – 9.2 11 1.0 Conditions – – V VGS = 0V, ID = 250µA 9.2 11 mΩ VGS = 4.5V, ID = 7A V VDS = VGS,ID = 250µA µA VDS = 24V, VGS = 0 1.0 30 30 150 150 ±100 ±100 Qg 22 31 22 31 VGS = 5V, ID = 7A Pre-Vth Gate-Source Charge Q gs1 3.7 3.7 VDS = 16V, ID = 7A Post-Vth Gate-Source Charge Q gs2 1.4 1.4 Gate to Drain Charge Qgd 6.8 6.8 Switch Charge* (Qgs2 + Qgd) QSW 8.2 11.5 8.2 Output Charge* Q oss 30 36 30 Gate Resistance Rg 1.7 1.7 Turn-on Delay Time td(on) 16 16 Rise Time tr 20 20 Turn-off Delay Time td (off) 38 38 Rg = 2Ω Fall Time tf 16 16 VGS = 4.5V Resistive Load VDS = 24V, VGS = 0, Tj = 100°C nA VGS = ±12V nC 36 VDS = 16V, VGS = 0 Ω VDD = 16V ns ID = 7A Source-Drain Rating & Characteristics Parameter Min Typ Max Min Typ Max Units Diode Forward Voltage* VSD Reverse Recovery Charge Qrr 88 88 Reverse Recovery Charge (with Parallel Schotkky) Notes: Qrr(s) 55 55 2 * 1.2 1.2 Conditions V IS = 7A, VGS = 0V nC di/dt = 700A/µs VDS = 16V, VGS = 0V, IS = 7A di/dt = 700A/µs (with 10BQ040) VDS = 16V, VGS = 0V, IS = 7A Repetitive rating; pulse width limited by max. junction temperature. Pulse width ≤ 300 µs; 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 4 Drain Current Control FET This can be expanded and approximated by; VGTH t0 2 Drain Voltage Figure 1: Typical MOSFET switching waveform Ploss = (Irms 2 × Rds(on) ) Synchronous FET Q f + I × gs2 × Vin × ig f + (Qg × Vg × f ) Q + oss × Vin × 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. www.irf.com t3 t1 QGD Ploss = Pconduction+ Pswitching+ Pdrive+ Poutput Q + I × gd × Vin × ig Gate Voltage t2 QGS1 Power losses in the control switch Q1 are given by; 1 QGS2 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. The power loss equation for Q2 is approximated by; * Ploss = Pconduction + Pdrive + Poutput ( 2 Ploss = Irms × Rds(on) ) + (Qg × Vg × f ) Q + oss × Vin × f + (Qrr × Vin × f ) 2 *dissipated primarily in Q1. 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 4 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 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 IRF7805A 10 ISD , Reverse Drain Current (A) ISD , Reverse Drain Current (A) 10 TJ = 150 ° C 1 TJ = 25 ° C V GS = 0 V 0.1 0.4 0.5 0.6 0.7 0.8 1 TJ = 25 ° C 0.1 0.4 0.9 VSD ,Source-to-Drain Voltage (V) Figure 9. Typical Source-Drain Diode Forward Voltage TJ = 150 ° C V GS = 0 V 0.5 0.6 0.7 0.8 0.9 VSD ,Source-to-Drain Voltage (V) Figure 10. Typical Source-Drain Diode Forward Voltage Thermal Response (Z thJA ) 100 D = 0.50 10 0.20 0.10 0.05 1 0.02 0.01 P DM SINGLE PULSE (THERMAL RESPONSE) t1 t2 0.1 0.001 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 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. 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