mic4417ym4 Micrel Semiconductor, mic4417ym4 Datasheet - Page 9

• Manufacturer Part Number: mic4417ym4
• Description: Mic4416/mic4417 Ittybitty? Low-side Mosfet Driver
• Manufacturer: Micrel Semiconductor

Power Dissipation
The maximum power dissipation must not be exceeded to
prevent die meltdown or deterioration.
Power dissipation in on/off switch applications is negligible.
Fast repetitive switching applications, such as SMPS (switch-
mode power supplies), cause a significant increase in power
dissipation with frequency. Power is dissipated each time
current passes through the internal output MOSFETs when
charging or discharging the external MOSFET. Power is also
dissipated during each transition when some current momen-
tarily passes from VS to GND through both internal MOSFETs.
Power dissipation is the product of supply voltage and supply
current:
1)
where:
Supply current is a function of supply voltage, switching
frequency, and load capacitance. Determine this value from
the “Typical Characteristics: Supply Current vs. Frequency”
graph or measure it in the actual application.
Do not allow P
T
ture) and the temperature rise across the thermal resistance
of the package. In another form:
2)
where:
Maximum power dissipation at 20°C with the driver soldered
to a 0.25in
The SOT-143 package θ
sistance) can be improved by using a heat sink larger than the
specified 0.25in
occurs through the large (GND) lead.
extension of the paddle to which the die is attached.
May 2005
MIC4416/4417
J
(junction temperature) is the sum of T
P
P
V
I
P
150 = absolute maximum junction temperature (°C)
T
220 = package thermal resistance (°C/W)
P
S
D
A
D
D
S
D (max)
= supply current (A) [see paragraph below]
= ambient temperature (°C) [68°F = 20°C]
= supply voltage (V)
= V
= power dissipation (W)
≤
2
150 T
ground plane is approximately 600mW.
S
220
= maximum power dissipation (W)
× I
D
−
Figure 4. Heat-Sink Plane
2
to exceed P
S
VS
G
A
ground plane. Significant heat transfer
PCB traces
JA
GND
CTL
(junction-to-ambient thermal re-
PCB heat sink/
D (max)
ground plane
, below.
A
(ambient tempera-
This lead is an
9
High-Frequency Operation
Although the MIC4416/7 driver will operate at frequencies
greater than 1MHz, the MOSFET’s capacitance and the load
will affect the output waveform (at the MOSFET’s drain).
For example, an MIC4416/IRL3103 test circuit using a 47Ω
5W load resistor will produce an output waveform that closely
matches the input signal shape up to about 500kHz. The
same test circuit with a 1kΩ load resistor operates only up to
about 25kHz before the MOSFET source waveform shows
significant change.
When the MOSFET is driven off, the slower rise occurs
because the MOSFET’s output capacitance recharges through
the load resistance (RC circuit). A lower load resistance
allows the output to rise faster. For the fastest driver opera-
tion, choose the smallest power MOSFET that will safely
handle the desired voltage, current, and safety margin. The
smallest MOSFETs generally have the lowest capacitance.
Figure 5. MOSFET Capacitance Effects at High
Logic
4.7µF
0.1µF
Input
+4.5V to 18V
Switching Frequency
3
4
VS
CTL
MIC4416
MOSFET’s drain
Slower rise time
observed at
GND
G
* International Rectifier
14m Ω , 30V MOSFET,
logic-level, V
2
1
G
+5V
GS
D
S
= ± 20V max.
1k Ω , 1/4W
47k Ω , 5W
Compare
loads
to
Logic-Level
MOSFET
IRL3103*
MIC4416/4417
Micrel, Inc.