MMDF5N02Z Datasheet, PDF (5/12 Pages) Motorola, Inc – DUAL TMOS POWER MOSFET 5.0 AMPERES 20 VOLTS

MMDF5N02Z
6
V_DS
5
QT
4
Q3
3
Q1
Q2
2
6
5
V_GS
4
3
2
1
I_D = 5 A ₁
T_J = 25°C
0
0
0
2
4
6
8
10
12
14
Q_g, TOTAL GATE CHARGE (nC)
Figure 8. Gate−To−Source and Drain−To−Source
Voltage versus Total Charge
1000 _{VDD = 6 V}
I_D = 5 A
V_GS = 4.5 V
T_J = 25°C
t_f
t_d(off)
t_r
100
t_d(on)
10
1
10
100
R_G, GATE RESISTANCE (OHMS)
Figure 9. Resistive Switching Time
Variation versus Gate Resistance
DRAIN−TO−SOURCE DIODE CHARACTERISTICS
The switching characteristics of a MOSFET body diode
are very important in systems using it as a freewheeling or
commutating diode. Of particular interest are the reverse re-
covery characteristics which play a major role in determin-
ing switching losses, radiated noise, EMI and RFI.
System switching losses are largely due to the nature of
the body diode itself. The body diode is a minority carrier de-
vice, therefore it has a finite reverse recovery time, t_rr, due
to the storage of minority carrier charge, Q_RR, as shown in
the typical reverse recovery wave form of Figure 11. It is this
stored charge that, when cleared from the diode, passes
through a potential and defines an energy loss. Obviously,
repeatedly forcing the diode through reverse recovery fur-
ther increases switching losses. Therefore, one would like a
diode with short t_rr and low Q_RR specifications to minimize
these losses.
The abruptness of diode reverse recovery effects the
amount of radiated noise, voltage spikes, and current ring-
ing. The mechanisms at work are finite irremovable circuit
parasitic inductances and capacitances acted upon by high
di/dts. The diode’s negative di/dt during t_a is directly con-
trolled by the device clearing the stored charge. However,
the positive di/dt during t_b is an uncontrollable diode charac-
teristic and is usually the culprit that induces current ringing.
Therefore, when comparing diodes, the ratio of t_b/t_a serves
as a good indicator of recovery abruptness and thus gives a
comparative estimate of probable noise generated. A ratio of
1 is considered ideal and values less than 0.5 are considered
snappy.
Compared to ON Semiconductor standard cell density
low voltage MOSFETs, high cell density MOSFET diodes
are faster (shorter t_rr), have less stored charge and a softer re-
verse recovery characteristic. The softness advantage of the
high cell density diode means they can be forced through re-
verse recovery at a higher di/dt than a standard cell MOS-
FET diode without increasing the current ringing or the
noise generated. In addition, power dissipation incurred
from switching the diode will be less due to the shorter re-
covery time and lower switching losses.
5
4.5
V_GS = 0 V
T_J = 25°C
4
3.5
3
2.5
2
1.5
1
0.5
0
0
0.1 0.2 0.3
0.4 0.5 0.6 0.7 0.8
V_SD, SOURCE−TO−DRAIN VOLTAGE (VOLTS)
Figure 10. Diode Forward Voltage versus Current
http://onsemi.com
5