MAX6397 MAXIM [Maxim Integrated Products], MAX6397 Datasheet - Page 12

• Manufacturer Part Number: MAX6397
• Description: Overvoltage Protection Switch/Limiter Controllers Operate Up to 72V
• Manufacturer: MAXIM [Maxim Integrated Products]

For stable operation over the full temperature range and
with load currents up to 100mA, use ceramic capacitor
values greater than 4.7µF. Large output capacitors help
reduce noise, improve load-transient response, and
power-supply rejection at REG. Note that some ceramic
dielectrics exhibit large capacitance and ESR variation
with temperature. At lower temperatures, it may be nec-
essary to increase capacitance.
Under normal conditions, use a 10µF capacitor at IN.
Larger input capacitor values and lower ESR provide bet-
ter supply-noise rejection and line-transient response.
Inrush current control can be implemented by placing a
capacitor at GATE (Figure 8) to slowly ramp up the
GATE, thus limiting the inrush current and controlling
GATE’s slew rate during initial turn-on. The inrush cur-
rent can be approximated using the following formula:
Overvoltage Protection Switch/Limiter
Controllers Operate Up to 72V
Figure 8. MAX6397/MAX6398 Controlling GATE Inrush Current
12
V
BATT
______________________________________________________________________________________
REG Capacitor Selection for Stability
I
INRUSH
MAX6397
MAX6398
GND
=
IN
C
C
GATE
OUT
GATE
Inrush/Slew-Rate Control
OUT
×
I
GATE
C
GATE
+
I
LOAD
C
OUT
LOAD
where I
the load current at startup, and C
capacitor.
When the external MOSFET is turned off during an over-
voltage occurrence, stray inductance in the power path
may cause voltage ringing exceeding the MAX6397/
MAX6398 absolute maximum input (IN) supply rating.
The following techniques are recommended to reduce
the effect of transients:
•
•
Add a resistor in series with IN to limit transient current
going into the input for the MAX6398 only.
Figure 9. Protecting the MAX6397/MAX6398 Input from High-
Voltage Transients
Minimize stray inductance in the power path using
wide traces, and minimize loop area including the
power traces and the return ground path.
Add a zener diode or transient voltage suppressor
(TVS) rated below the IN absolute maximum rating
(Figure 9).
V
BATT
GATE
TVS
60V
is GATE’s 75µA sourcing current, I
MAX6397
MAX6398
GND
IN
1kΩ
Input Transients Clamping
GATE
OUT
OUT
is the output
LOAD
LOAD
is