MMDF2P01HD Datasheet, PDF (5/12 Pages) Motorola, Inc – DUAL TMOS POWER FET 2.0 AMPERES 12 VOLTS

MMDF2P01HD
5
10
QT
4
V_DS
3
8
V_GS
6
2 _Q1
Q2
I_D = 2 A
4
T_J = 25°C
1
2
Q3
0
0
0
2
4
6
8
10
Q_T, TOTAL CHARGE (nC)
Figure 8. Gate−To−Source and Drain−To−Source
Voltage versus Total Charge
1000
V_DD = 6 V
I_D = 2 A
V_GS = 4.5 V
T_J = 25°C
100
t_d(off)
t_f
t_r
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
recovery characteristics which play a major role in
determining 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
device, 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 14. 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
further 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
ringing. 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
controlled by the device clearing the stored charge.
However, the positive di/dt during t_b is an uncontrollable
diode characteristic 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
reverse recovery characteristic. The softness advantage of
the high cell density diode means they can be forced through
reverse recovery at a higher di/dt than a standard cell
MOSFET 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
recovery time and lower switching losses.
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