Introduction and Basic Characteristics
3–18
Motorola TMOS Power MOSFET Transistor Device Data
Absolute Maximum Ratings
Absolute maximum ratings represent the extreme capabili-
ties of the device. They can best be described as device
characterization boundaries and are given to facilitate “worst
case” design.
Drain–to–Source Voltage (V
DSS
, V
DGR
)
– This represents
the lower limit of the devices blocking voltage capability from
drain–to–source when either the gate is shorted to the
source (V
DSS
), or when a 1 MΩ gate–to–source resistor is
present (V
DGR
). It is measured at a specific leakage current
and has a positive temperature coefficient. The voltage
across the Power MOSFET should never exceed this rating
in order to prevent breakdown of the drain–to–source
junction.
Maximum Gate–to–Source Voltage (V
GS
, V
GSM
)
– The
maximum allowable gate–to–source voltage as either a con-
tinuous condition (V
GS
), or as a single pulse non–repetitive
condition (V
GSM
). Exceeding this limit may result in perma-
nent device degradation.
Continuous Drain Current (I
D
)
– The dc current level that
will raise the devices junction temperature to it’s rated maxi-
mum while it’s reference temperature is held at 25°C. This
can be calculated by the equation:
I
D
where,
= SQRT (P
D
/R
DS(on)
@ MAX T
J
)
SQRT
P
D
R
DS(on)
MAX T
J
= Square root
= Device’s maximum power dissipation
= Device’s “on” resistance
= Device’s maximum rated junction temperature
Pulsed Drain Current (I
DM
)
– The maximum allowable peak
drain current the device can safely handle under a 10 µs
pulsed condition. This rating takes into consideration the de-
vices thermal limitation as well as R
DS(on)
, wire bond and
source metal limitations.
Drain–to–Source Avalanche Energy (EAS)
– This specifi-
cation defines the maximum allowable energy that the device
can safely handle in avalanche due to an inductive current
spike. It is tested at the I
D
of the device as a single pulse
non–repetitive condition. This value has a negative tempera-
ture coefficient as shown by the “Maximum Avalanche Ener-
gy versus Starting Junction Temperature” figure shown in the
data sheet. For repetitive avalanche conditions, this value
should be derated using the “Thermal Response” figure
shown in the data sheet for calculating the junction tempera-
ture and the “Maximum Avalanche Energy versus Starting
Junction Temperature” figure also shown in the data sheet.
Maximum Power Dissipation (P
D
)
– Specifies the power
dissipation limit which takes the junction temperature to it’s
maximum rating while the reference temperature is being
held at 25°C. It is calculated by the following equation:
P
D
where,
= (T
J
– T
r
)/R
thjr
P
D
T
J
T
r
R
thjr
= Maximum power dissipation
= Maximum allowable junction temperature
= Reference (case and or ambient) temperature
= Thermal resistance junction–to–reference
= (case or ambient)
Junction Temperature (T
J
)
– This value represents the
maximum allowable junction temperature of the device. It is
derived and based off of long term Reliability data. Exceed-
ing this value will only serve to shorten the device’s long term
operating life.
Thermal Resistance (R
thjc
, R
thja
)
– The quantity that resists
or impedes the flow of heat energy in a device is called ther-
mal resistance. Thermal resistance values are needed for
proper thermal design. These values are measured as de-
tailed in Motorola Application Note AN1083.
Electrical Characteristics
The intent of this section in the data sheet is to provide de-
tailed device characterization so that the designer can pre-
dict with a high degree of accuracy the behavior of the device
in a specific application.
Drain–to–Source Breakdown Voltage (V
(BR)DSS
)
– As de-
scribed earlier, this represents the lower limit of the devices
blocking voltage capability from drain–to–source with the
gate shorted to the source. It is measured at a specific leak-
age current and has a positive temperature coefficient.
Zero Gate Voltage Drain Current (I
DSS
)
– The direct current
into the drain terminal of the device when the gate–to–source
voltage is zero and the drain terminal is reversed biased with
respect to the source terminal. This parameter generally in-
creases with temperature as shown in the “Drain–to–Source
Leakage Current versus Voltage” figure found in the device’s
data sheet.
Gate–Body Leakage Current (I
GSS
)
– The direct current
into the gate terminal of the device when the gate terminal is
biased with either a positive or negative voltage with respect
to the source terminal and the drain terminal is short–
circuited to the source terminal.
Gate Threshold Voltage (V
GS(th)
)
– The forward gate–to–
source voltage at which the magnitude of drain current has
been increased to some low threshold value, usually
specified as 250 µA or 1 mA. This parameter has a negative
temperature coefficient.
Drain–to–Source On–Resistance (R
DS(on)
)
– The dc resis-
tance between the drain–to–source terminals with a speci-
fied gate–to–source voltage applied to bias the device into
the on–state. This parameter has a positive temperature
coefficient.
Drain–to–Source On–Voltage (V
DS(on)
)
– The dc voltage
between the drain–to–source terminals with a specified
gate–to–source voltage applied to bias the device into the
on–state. This parameter has a positive temperature coeffi-
cient.
Forward Transconductance (g
FS
)
– The ratio of the
change in drain current due to a change in gate–to–source
voltage (i.e., ∆ I
D
/∆ V
GS
).
Device Capacitance (C
iss
, C
oss
, C
rss
)
– Power MOSFET
devices have internal parasitic capacitance from terminal–
to–terminal. This capacitance is voltage dependent as
shown by the “Capacitance Variation” figure on the device’s
data sheet. C
iss
is the capacitance between the gate–to–
source terminals with the drain terminal short–circuited to the
source terminal for alternating current. C
oss
is the capaci-
tance between the drain–to–source terminals with the gate