MAX9940 Maxim Integrated Products, MAX9940 Datasheet - Page 6

• Manufacturer Part Number: MAX9940
• Description: Signal-Line Overvoltage Protector
• Manufacturer: Maxim Integrated Products

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Signal-Line Overvoltage Protector
for Low-Voltage Devices
In all three schemes, the MAX9940 protects the micro-
controller from both DC fault voltages above V
ESD strikes on EXT. The difference in the three
schemes lies in the impact on power consumption in
battery-operated devices during normal and short to
GND fault conditions.
Figure 1 shows a recommended configuration for battery-
operated devices that need to conserve power both on
a continuous basis as well as during short to GND fault
conditions. In this scheme, the ENABLE port of a micro-
controller supplies the quiescent current for the
MAX9940 as well as that required for digital communi-
cation (i.e., R
ENABLE digital output port of the microcontroller, the
MAX9940 is in a zero-power shutdown mode, while also
preventing any power drain to occur in the event of a
short to GND fault on EXT. As stated earlier, EXT main-
tains the ability to withstand DC voltages up to 28V
even when V
In Figure 2, the ENABLE port of a microcontroller pow-
ers the MAX9940. The low 13µA operating current
allows standard digital I/O ports to easily supply the
Figure 1. Recommended Scheme for Battery-Operated Devices that Need to Shut Down the MAX9940 and Prevent Power Draw
During Short to GND Faults
6
_______________________________________________________________________________________
CC
P
pullup resistor). By forcing a 0 on the
= 0.
MICROCONTROLLER
Rx
Tx
ENABLE
DATA
V
DD
= 3.3V
2kΩ
CC
R
P
and
INT
operating current of the MAX9940 without any substan-
tial voltage drop (V
ENABLE port of the microcontroller, the MAX9940 can
be put into a zero-power mode, thus conserving battery
power. It should be noted that there is no internal ESD
diode from INT to V
stay at V
rent from R
does exist from INT to EXT, and therefore, in the event
of a short to GND fault on EXT, current is drawn through
R
ly reduce battery life.
In Figure 3, V
consumes quiescent current on a continuous basis. In
this mode, the internal FET between INT and EXT is
kept on as long as the voltage on EXT is below V
a result, in the event of a short to GND fault on EXT,
current is drawn through RP, causing a power drain
from V
GND
P
MAX9940
, causing a power drain from V
V
DD
CC
DD
and potentially reducing battery life.
P
even though V
or the battery. However, an internal diode
EXT
DD
powers the MAX9940 directly, and
CC
OH
1-Wire
DEVICE
. This allows the voltage at INT to
≈ V
Tx
CC
DD
Rx
= 0, thus drawing no cur-
). By forcing a 0 on the
DD
, and can potential-
CC
. As