MIC2584-JBTS Micrel Inc, MIC2584-JBTS Datasheet - Page 24

• Manufacturer Part Number: MIC2584-JBTS
• Description: IC CTRLR HOT SWAP DUAL 16-TSSOP
• Manufacturer: Micrel Inc
• Type: Hot-Swap Controllerr

Specifications of MIC2584-JBTS

• Applications: General Purpose
• Internal Switch(s): No
• Voltage - Supply: 1 V ~ 13.2 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TSSOP
• Linear Misc Type: Positive Low Voltage
• Family Name: MIC2584
• Package Type: TSSOP
• Operating Supply Voltage (min): 1V
• Operating Supply Voltage (max): 13.2V
• Operating Temperature (min): -40C
• Operating Temperature (max): 85C
• Operating Temperature Classification: Industrial
• Product Depth (mm): 4.4mm
• Product Height (mm): 0.9mm
• Product Length (mm): 5mm
• Mounting: Surface Mount
• Pin Count: 16
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

MIC2584/2585
MOSFET Steady-State Thermal Issues
The selection of a MOSFET to meet the maximum continuous
current is a fairly straightforward exercise. First, arm yourself
with the following data:
The data sheet will almost always give a value of on resis-
tance given for the MOSFET at a gate-source voltage of 4.5V,
and another value at a gate-source voltage of 10V. As a first
approximation, add the two values together and divide by two
to get the on-resistance of the part with 8V of enhancement.
Call this value R
as an ohmic (resistive) device, almost all that’s required to
determine steady-state power dissipation is to calculate I
The one addendum to this is that MOSFETs have a slight
increase in R
approximation for this value is 0.5% increase in R
rise in junction temperature above the point at which R
initially specified by the manufacturer. For instance, if the
selected MOSFET has a calculated R
T
at 110 C, a good first cut at the operating value for R
would be:
MIC2584/2585
J
= 25 C, and the actual junction temperature ends up
• The value of I
• The manufacturer’s data sheet for the candidate
• The maximum ambient temperature in which the
• Any knowledge you can get about the heat
question (see "
MOSFET.
device will be required to operate.
sinking available to the device (e.g., can heat be
dissipated into the ground plane or power plane,
if using a surface-mount part? Is any airflow
available?).
ON
ON
with increasing die temperature. A good
Undervoltage (Output) = 11.0V
/POR Delay = 25ms
START-UP Delay = 6ms
*Recommended for MOSFETs with gate-source
breakdown of 20V or less for catastrophic output
short circuit protection. (IRF7822 V GS (MAX) = 12V)
Channel 2 and additional pins omitted for clarity.
. Since a heavily enhanced MOSFET acts
12V
V
IN
LOAD(CONT, MAX.)
Sense Resistor Selection
33k
33k
R1
R2
(18V)
D1
for the output in
Figure 12. Zener Clamped MOSFET Gate
0.05 F
ON
C1
1 F
6
C3
of 10m
ON
CPOR
VCC1
3
").
16
1
7
R
0.006
ON
SENSE1
5%
MIC2584
ON
SENSE1
per C
GND
2
at a
4
was
15
9
2
ON
R.
24
GATE1
/POR
The final step is to make sure that the heat sinking available
to the MOSFET is capable of dissipating at least as much
power (rated in C/W) as that with which the MOSFET’s
performance was specified by the manufacturer. Here are a
few practical tips:
MOSFET Transient Thermal Issues
Having chosen a MOSFET that will withstand the imposed
voltage stresses, and the worse case continuous I
dissipation which it will see, it remains only to verify the
MOSFET’s ability to handle short-term overload power dissi-
pation without overheating. A MOSFET can handle a much
FB1
1. The heat from a surface-mount device such as
2. Airflow works. Even a few LFM (linear feet per
3. The best test of a surface-mount MOSFET for
14
12
11
IRF7822
(SO-8)
R
Q1
an SO-8 MOSFET flows almost entirely out of
the drain leads. If the drain leads can be sol-
dered down to one square inch or more, the
copper will act as the heat sink for the part. This
copper must be on the same layer of the board
as the MOSFET drain.
minute) of air will cool a MOSFET down sub-
stantially. If you can, position the MOSFET(s)
near the inlet of a power supply’s fan, or the
outlet of a processor’s cooling fan.
an application (assuming the above tips show it
to be a likely fit) is an empirical one. Check the
MOSFET's temperature in the actual layout of
the expected final circuit, at full operating
current. The use of a thermocouple on the drain
leads, or infrared pyrometer on the package, will
then give a reasonable idea of the device’s
junction temperature.
ON
DOWNSTREAM
SIGNAL
R3
10
C2
0.01 F
10m [1 + (110 - 25)(0.005)]
*D2
1N5240B
10V
R4
100k
1%
R5
13.3k
1%
C
220 F
LOAD1
12V@6A
V
OUT
14.3m
March 2005
2
R power
Micrel