MIC4223 Datasheet, PDF (11/20 Pages) Micrel Semiconductor – Dual 4A, 4.5V to 18V, 15ns Switch Time, Low-Side MOSFET Drivers with Enable

Micrel, Inc.
Quiescent Current Power Dissipation
Quiescent current powers the internal logic, level shifting
circuitry and bias for the output drivers. This current is
proportional to operating frequency and V_DD voltage. The
typical characteristic graphs show how supply current
varies with switching frequency and supply voltage.
The power dissipated by the driver’s quiescent current is:
Pdiss_quiescent = V_DD × I _DD
Total Power Dissipation and Thermal Considerations
Total package power dissipation equals the power
dissipation of each driver caused by driving the external
MOSFETs plus the supply current.
Pdiss_TOTAL = Pdiss_quiescent + Pdriver_A + Pdriver_B
The die temperature may be calculated once the total
power dissipation is known.
T_J = T_A + Pdiss_TOTAL × θ _JA
Where:
T_A is the Maximum ambient temperature
T_J is the junction temperature (°C)
Pdiss_TOTAL is the power dissipation of the Driver
θ_JA is the thermal resistance from junction-to-
ambient air (°C/W)
The following graphs help determine the maximum gate
charge that can be driven with respect to switching
frequency, supply voltage and ambient temperature.
Figure 5a shows the power dissipation in the driver for
different values of gate charge with V_DD = 5V. Figure 5b
shows the power dissipation at V_DD = 12V. Figure 5c show
the maximum power dissipation for a given ambient
temperature for the SOIC and ePAD MSOP packages.
The maximum operating frequency of the driver may be
limited by the maximum power dissipation of the driver
package.
MIC4223/MIC4224/MIC4225
PDISS: GATE Charge
vs. Frequency
1.4
V_DD=5V
1.2
50nC
1.0
40nC
0.8
30nC
0.6
20nC
0.4
0.2
10nC
0
100k
1M
10M
FREQUENCY (Hz)
Figure 5a. P_DISS vs. Q_G and f_S for V_DD = 5V
PDISS: GATE Charge
vs. Frequency
2.0
1.8 ^VDD=12V
50nC ^40nC
30nC
1.6
1.4
1.2
20nC
1.0
0.8
0.6
10nC
0.4
0.2
0
100k
1M
10M
FREQUENCY (Hz)
Figure 5b. P_DISS vs. Q_G and f_S for V_DD = 12V
Maximum Power
Dissipation
2.0
1.5
1.0
0.5
0.0
20 40 60 80 100 120 140
Ambient Temperature (°C)
Figure 5c. Maximum P_DISS vs. Ambient Temperature
June 2009
11
M9999-061109-A
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