MAX14670 Datasheet, PDF (10/13 Pages) Maxim Integrated Products – Bidirectional Current-Blocking, High-Input Overvoltage Protector with Adjustable OVLO

MAX14670–MAX14673
Bidirectional Current-Blocking, High-Input
Overvoltage Protector
with Adjustable OVLO
Detailed Description
The MAX14670–MAX14673 overvoltage protection
(OVP) devices feature low on-resistance (R_ON) internal
FETs (Q1+Q2) and protect low-voltage systems against
voltage faults up to +28V_DC. An internal clamp also
protects the devices from surges up to +80V. If the input
voltage exceeds the overvoltage threshold, the output
is disconnected from the input to prevent damage to
the protected components. The 15ms debounce time
prevents false turn-on of the internal FETs during startup.
Soft-Start
To minimize inrush current, the devices feature a soft-start
capability to slowly turn on Q1 and Q2. Soft-start begins
when ACOK/ACOK is asserted and ends after 15ms (typ).
Overvoltage Lockout (OVLO)
Connect OVLO to ground to use the internal OVLO
comparator with the internally set OVLO value. When
IN goes above the overvoltage lockout threshold
(V_{IN_OVLO}), OUT is disconnected from IN and ACOK/
ACOK is deasserted. When IN drops below V_{IN_OVLO},
the debounce time starts counting. After the debounce
time, OUT follows IN again and ACOK/ACOK is asserted.
External OVLO Adjustment Functionality
When an external resistor-divider is connected to
OVLO and V_OVLO exceeds the OVLO select voltage
(V_{OVLO_SEL}), the internal OVLO comparator reads IN by
the external resistor-divider.
R1 = 1MΩ is a good starting value for minimum current
consumption. Since V_{IN_OVLO}, V_{OVLO_TH}, and R1 are
known, R2 can be calculated from the following formula:
This external resistor-divider is completely independent
from the internal resistor-divider.
Reverse Bias Blocking
The ICs feature reverse bias blocking. When IN voltage
is below input startup voltage and OTG_EN is low, the
switch between IN and OUT is open and the two back-
to-back diodes of the two series switches block reverse
bias. Therefore, when the voltage is applied at the output,
current does not travel back to the input. When OVLO is
high, the parts block against reverse bias as well.
OTG Enable
The devices feature reverse turn-on capability. OTG_EN
can be used to turn on the switch for OUT to feed back
to IN when the voltage applied at OUT is above the mini-
mum startup voltage. When OTG_EN is high, ACOK and
ACOK are deasserted. During the OTG operation, if IN
goes above OVLO, the OVP switch turns off. It is recom-
mended that the power is supplied to OUT prior to OTG
operation and also the power is removed from OUT prior
to disable OTG operation.
Thermal Shutdown Protection
The devices feature thermal shutdown protection to pro-
tect the devices from overheating. The internal FETs turn
off when the junction temperature exceeds +150°C (typ),
and the device returns to normal operation after the tem-
perature drops by approximately 20°C (typ).
Applications Information
IN Bypass Capacitor
If desired, bypass IN to GND with a 0.1µF ceramic capaci-
tor as close to the device as possible. If the power source
has significant inductance due to long lead length, the
device prevents overshoots due to the LC tank circuit and
provides protection by clamping the overshooting.
Output Capacitor
The slow turn-on time provides a soft-start function that
allows the devices to charge an output capacitor up to
1000µF without turning off due to an overcurrent condi-
tion. Bypass OUT to GND with a minimum of 1µF ceramic
capacitor.
Extended ESD Protection
ESD protection structures are incorporated on all pins
to protect against electrostatic discharges up to ±2kV
(Human Body Model) encountered during handling and
assembly. IN is further protected against ESD up to ±15kV
(HBM), ±15kV (Air-Gap Discharge method described in
IEC 61000-4-2) and ±8kV (Contact Discharge Method
described in IEC 61000-4-2) without damage.
The ESD structures withstand high ESD both in normal
operation and when the device is powered down. After an
ESD event, the MAX14670–MAX14673 continue to func-
tion without latchup.
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