MAX4838 Maxim, MAX4838 Datasheet - Page 7

• Manufacturer Part Number: MAX4838
• Description: Overvoltage Protection Controllers with Status FLAG
• Manufacturer: Maxim

The MAX4838–MAX4841 can be used with either a sin-
gle MOSFET configuration as shown in the Typical
Operating Circuit, or can be configured with a back-to-
back MOSFET as shown in
The MAX4838–MAX4841 can drive either a single
MOSFET or back-to-back MOSFETs. The back-to-back
configuration has almost zero reverse current when the
input supply is below the output.
If reverse current leakage is not a concern, a single
MOSFET can be used. This approach has half the loss
of the back-to-back configuration when used with simi-
lar MOSFET types, and is a lower cost solution. Note
that if the input is actually pulled low, the output is
pulled low as well due to the parasitic body diode in the
MOSFET. If this is a concern, then the back-to-back
configuration should be used.
Figure 6. State Diagram
V
IN
< UVLO
Applications Information
_______________________________________________________________________________________
Overvoltage Protection Controllers with
GATE DRIVEN HIGH
TIMER STARTS
OVLO CHECK
FLAG = HIGH
FLAG = LOW
FLAG = LOW
FLAG = LOW
GATE HIGH
COUNTING
STANDBY
STARTUP
GATE = 0
GATE = 0
MOSFET Configuration
ON
Figure
V
V
t = 50ms
t = 50ms
IN
IN
> UVLO
< OVLO
7.
V
IN
> OVLO
The MAX4838–MAX4841 are designed for use with
either a single N-channel MOSFET or dual back-to-
back N-channel MOSFETs. In most situations,
MOSFETs with R
work well. If the input supply is near the UVLO maxi-
mum of 3.5V consider using a MOSFET specified for a
lower V
MOSFET to withstand the full 28V IN range of the
MAX4838–MAX4841.
MOSFETs appropriate for use with the MAX4838–
MAX4841.
For most applications, bypass IN to GND with a 1µF
ceramic capacitor. If the power source has significant
inductance due to long lead length, take care to pre-
vent overshoots due to the LC tank circuit and provide
protection if necessary to prevent exceeding the 30V
absolute maximum rating on IN.
The MAX4838–MAX4841 provide protection against volt-
age faults up to 28V, but this does not include negative
voltages. If negative voltages are a concern, connect a
Schottky diode from IN to GND to clamp negative
input voltages.
ESD performance depends on a number of conditions.
The MAX4838–MAX4841 are specified for 15kV typical
ESD resistance on IN when IN is bypassed to ground
with a 1µF ceramic capacitor. Contact Maxim for a reli-
ability report that documents test setup, methodology,
and results.
Figure 7. Back-to-Back External MOSFET Configuration
0 TO 28V
INPUT
1µF
GS
voltage. Also the V
1
6
2
DS(ON)
IN
EN
GND
MAX4838–
MAX4841
IN Bypass Considerations
Table
Status FLAG
specified for a V
FLAG
GATE
ESD Test Conditions
DS
1 shows a selection of
MOSFET Selection
should be 30V for the
4
3
NMOS
NOTE: EN AND PULLUP
RESISTOR ON MAX4838/
MAX4840 ONLY.
V
IO
GS
OUTPUT
of 4.5V
7