MAX6397SATA+T Maxim Integrated Products, MAX6397SATA+T Datasheet - Page 13

• Manufacturer Part Number: MAX6397SATA+T
• Description: IC SW OVERVOLT PROT 8-TDFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX6397SATA+T

• Voltage - Working: 72V
• Technology: Mixed Technology
• Power (watts): 1.45W
• Number Of Circuits: 1
• Applications: General Purpose
• Package / Case: 8-TDFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Voltage - Clamping: -

Figure 10. Power Dissipated Across MOSFETs During an
Overvoltage Fault (Overvoltage Limiter Mode)
Select external MOSFETs according to the application
current level. The MOSFET’s on-resistance (R
should be chosen low enough to have minimum voltage
drop at full load to limit the MOSFET power dissipation.
Determine the device power rating to accommodate
an overvoltage fault when operating the MAX6397/
MAX6398 in overvoltage limit mode.
During normal operation, the external MOSFETs dissipate
little power. The power dissipated in normal operation is:
The most power dissipation will occur during a pro-
longed overvoltage event when operating the
MAX6397/MAX6398 in voltage limiter mode, resulting in
high power dissipated in Q1 (Figure 10) where the
power dissipated across Q1 is:
where V
and source.
The MAX6397/MAX6398 thermal-shutdown feature shuts
off the linear regulator output, REG, and GATE if it
exceeds the maximum allowable thermal dissipation.
Thermal shutdown also monitors the PC board tempera-
ture of the external nFET when the devices sit on the
V
BATT
TVS
60V
Q1
V
MAX
is the voltage across the MOSFET’s drain
P
Q1
______________________________________________________________________________________
P
MAX6397
MAX6398
Q1
= I
GND
IN
LOAD
Overvoltage Protection Switch/Limiter
= V
GATE
OUT
Q1
SET
2
+
x R
x I
V
Q1
Thermal Shutdown
LOAD
DS(ON).
-
MOSFET Selection
I
LOAD
LOAD
V
Controllers Operate Up to 72V
BATT
DS(ON)
V
OV
)
same thermal island. Good thermal contact between the
MAX6397/MAX6398 and the external nFET is essential
for the thermal-shutdown feature to operate effectively.
Place the nFET as close as possible to OUT.
When the junction temperature exceeds T
the thermal sensor signals the shutdown logic, turning off
REG’s internal pass transistor and the GATE output,
allowing the device to cool. The thermal sensor turns
the pass transistor and GATE on again after the IC’s
junction temperature cools by 20°C. Thermal-overload
protection is designed to protect the MAX6397/
MAX6398 and the external MOSFET in the event of cur-
rent-limit fault conditions. For continuous operation, do
not exceed the absolute maximum junction-tempera-
ture rating of T
When operating the MAX6397/MAX6398 in overvoltage
limit mode for a prolonged period of time, a thermal
shutdown is possible due to device self-heating. The
thermal shutdown is dependent on a number of differ-
ent factors:
•
•
•
•
•
•
Figure 11. MAX6397/MAX6398 Timing Diagram
GATE
OUT
The device’s ambient temperature (T
The output capacitor (C
The output load current (I
The overvoltage threshold limit (V
The overvoltage waveform period (t
The power dissipated across the package (P
J
= +150°C.
t
1
OUT
Overvoltage Limiter Mode
OUT
Thermal Shutdown
)
t
OVP
t
2
)
OV
t
3
OVP
)
A
)
)
J
= +150°C,
DISS
)
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