MAX4971EVKIT+ Maxim Integrated, MAX4971EVKIT+ Datasheet - Page 6

• Manufacturer Part Number: MAX4971EVKIT+
• Description: Power Switch ICs - Power Distribution Overvoltage-Protection Controllers with a Low RON Internal FET
• Manufacturer: Maxim Integrated

Specifications of MAX4971EVKIT+

• On Resistance (max): 90 mOhms
• On Time (max): 13 ms
• Off Time (max): 8 us
• Operating Supply Voltage: 2.2 V to 28 V
• Maximum Power Dissipation: 678 mW

Overvoltage-Protection Controllers
with a Low R
The MAX4970/MAX4971/MAX4972 overvoltage protec-
tion devices feature a low R
low-voltage systems against voltage faults up to +28V.
If the input voltage exceeds the overvoltage threshold,
the internal MOSFET is turned off to prevent damage to
the protected components. These devices also drive an
optional external pFET to protect against reverse-polari-
ty input voltages. The 15ms debounce time prevents
false turn-on of the internal nFET during startup.
The MAX4970/MAX4971/MAX4972 have timing logic
that control the turn-on of the internal nFET. The timing
logic controls the turn-on of the charge pump and the
state of the open-drain ACOK output. If V
if V
pump. If V
pump is enabled. The charge-pump startup, after a
15ms debounce delay, turns on the internal nFET (see
the Functional Diagram ). ACOK is high impedance dur-
ing startup until the ACOK 15ms debounce period
expires. At this point, the device is in its on state. At any
time, if V
the charge pump is disabled.
6
IN
_______________________________________________________________________________________
> V
IN
OVLO
UVLO
ACOK
drops below V
GP
IN
, the timing logic disables the charge
< V
MAX4970
MAX4971
MAX4972
IN
R
R
Detailed Description
GPPU
GPPD
< V
UVLO
ON
OVLO
internal FET and protect
ON
or rises above V
Device Operation
, the internal charge
Internal FET
IN
< V
REFERENCE
UVLO
V
BG
OVLO
or
,
GND
+
-
+
The MAX4970/MAX4971/MAX4972 incorporate an inter-
nal nFET with a 40mΩ (typ) R
driven by a charge pump that generates a 5V voltage
above IN. The internal nFET is equipped with 2.3A (min)
current-limit protection that turns off the nFET within
10µs (typ) during an overcurrent fault condition.
The MAX4970/MAX4971/MAX4972 have an overcurrent
autoretry function that turns on the nFET again after a
15ms (typ) retry time (see Figure 2). The fast turn-off
time and 15ms retry time result in a very low duty cycle
to keep power consumption low. If the faulty load con-
dition is not present, the nFET remains on.
The GP gate drive is controlled by internal logic and by
the EN input. When EN is high, the internal pullup
between GP and IN is active, thus disabling the exter-
nal pFET, and the load is protected against negative
voltages down to the voltage rating of the external
pFET. When EN is active (low), and the input voltage at
IN is above the UVLO threshold, the pulldown between
GP and IN is active, thus enabling the external pFET.
-
TEMPERATURE
FAULTS
OVERCURRENT
FAULT
EN
Functional Diagram
RETRY TIME
OSCILLATOR
DEBOUNCE
TIMER AND
CONTROL
CHARGE
LOGIC
PUMP
15ms
ON
START
. The nFET is internally
Internal nFET
GP gate Drive
OUT
EN
Autoretry