MC33981BPNA Freescale, MC33981BPNA Datasheet - Page 28

• Manufacturer Part Number: MC33981BPNA
• Manufacturer: Freescale

Specifications of MC33981BPNA

• Switch Type: High Side
• Power Switch Family: MC33981B
• Power Switch On Resistance: 6mOhm
• Output Current: 40A
• Number Of Outputs: Single
• Mounting: Surface Mount
• Supply Current: 10mA
• Package Type: Power QFN
• Operating Temperature (min): -40C
• Operating Temperature Classification: Automotive
• Pin Count: 16
• Lead Free Status / RoHS Status: Compliant

JUNCTION TEMPERATURE
knowing the power dissipation and the thermal
characteristics of the PC board with this formula:
where T
temperature, and R
ambient.
RECIRCULATION PHASE
handled by an external freewheeling diode. With the 33981,
28
33981
TYPICAL APPLICATIONS
POWER DISSIPATION
The junction temperature of the 33981 can be calculated
In standard configuration, the motor current recirculation is
90
80
70
60
50
40
30
20
10
120
100
0
80
60
40
20
Figure 36. Positive and Negative Slew Rate
0
Figure 37. OUT switching vs. SR Capacitor
J
T
is the junction temperature, T
J
4.5
= T
4.5
A
+ (Pon_state + Pswitching). R
THJA
6
vs. SR Capacitor
6
the thermal impedance junction to
Vbat
Vbat
9
9
14
14
A
the ambient
27
27
THJA
0
1
2.2
3.3
4.7
6.8
0
1
2.2
3.3
4.7
6.8
the freewheeling diode can be replaced by an external low-
side discrete MOSFET.
calculated as follows for the diode and the low-side MOSFET
respectively:
where ‘a’ is the duty cycle
where R
APPLICATIONS EXAMPLES
EXCEL TOOL
to calculate the dissipated power and the junction
temperature knowing the application conditions. An example
of the interface is given in
concern the load, the high-side device, the recirculation, and
the board. They are V
100% of duty cycle), PWM frequency, 33981 R
150ºC, SR capacitor, low-side R
temperature, and thermal impedance.
the 33981 and the low side. The current is also considered
constant in the load. The model taken for the V
is (0.4 + 0.01 . I
the entire document.
Recirculation
Device (HS)
The power dissipation during the recirculation phase is
An excel tool has been created with all the above formulas
The calculations are done with the maximum R
The listed conditions in
High Side
Board
Load
DS(ON)_ls
Pmosfet_ls = (1-a) . R
OUT
Frequency
T ambiant
Capacitor
Pdiode = (1-a) . V
is the on resistance of the low side.
@150°C
@150°C
R
R
Figure 38. Excel Tool
) Volts.
Rthja
Vpwr
Imax
DSON
DSON
SR
PWR
Analog Integrated Circuit Device Data
Figure
Low Side Characteristics
, DC current in the load (Imax for
Figure 38
INPUTS
DS(ON)
38. The parameters to enter
DS(ON)_ls
Freescale Semiconductor
F
are the ones chosen for
. I
OUT
12 V
20 A
20 KHz
6.8 mOhm
0 nF
20 mOhm
15 °C/W
85 °C
at 150ºC, ambient
. I
OUT
F
DS(ON)
of the diode
2
DS(ON)
at
for