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MAX4893BETB+T

P1-P3P4-P6P7-P9P10-P12P13-P13
Detailed Description
The MAX4881–MAX4884/MAX4893B provide up to
+28V overvoltage protection for low-voltage systems.
When the input voltage at IN exceeds the overvoltage
trip level (OVLO), the MAX4881–MAX4884/MAX4893B
turn off the low-cost external n-channel FET to prevent
damage to the protected components and issue an
overvoltage fault flag.
The MAX4881–MAX4884 feature a built-in current-limited
switch that limits the load current to 1.1A (MAX4881/
MAX4882), 0.7A (MAX4883B/MAX4883C/MAX4884B/
MAX4884C), and 0.9A (MAX4893B). When the load cur-
rent is at the current limit for longer than the blanking
time, the switch of the MAX4881/MAX4882/MAX4883B/
MAX4884B/MAX4893B latches off and does not turn
back on until EN or CB or IN is cycled. A current-limit flag
(FLAGI) asserts to indicate a current fault condition. The
MAX4883C/MAX4884C limit the current to 0.7A indefinite-
ly until the thermal protection trips. An overcurrent flag
output asserts to indicate a current fault condition after
the blanking time has elapsed.
IN-Undervoltage Lockout (UVLO)
The MAX4881/MAX4883/MAX4893B have a fixed 4.35V
undervoltage lockout level (UVLO) while the
MAX4882/MAX4884 have a fixed UVLO of 2.55V. GATE
goes low when V
IN
is below V
UVLO
, turning off the
external n-channel FET.
IN-Overvoltage Lockout (OVLO)
The MAX4881/MAX4883/MAX4893B have a fixed 5.6V
overvoltage threshold (OVLO), while the MAX4882/
MAX4884 have a fixed OVLO of 4.5V. GATE goes low
when V
IN
is higher than V
OVLO
, turning off the external
n-channel FET.
Fault Flag Output (
OV
)
The OV output signals the host system that there is a fault
with the input voltage. OV asserts low in response to
either an overvoltage or undervoltage fault. OV stays low
for 50ms after GATE turns on, before deasserting high.
OV is an open-drain active-low output. Connect a
pullup resistor from OV to the logic I/O voltage of the
host system or to any voltage source up to 6V. Driving
EN high disables OV.
MAX4881–MAX4884/MAX4893B
Overvoltage Protection Controllers with
Current Limit in TDFN
_______________________________________________________________________________________ 7
V
IN
1.2V
V
GATE
V
UVLO
0.3V
t
START
2.4V
t
0V-BLANK
8V
t
GON
V
OV
5V
Figure 1. Startup Timing Diagram
V
IN
V
GATE
V
OVLO
0.3V
t
GOFF
0.4V
t
OV
4V/5V
7V/8V
V
OV
Figure 2. Shutdown Timing Diagram
V
IN
I
GATE
V
OVLO
80%
t
OVP
0V
Figure 3. Power-Up Overvoltage Timing Diagram
V
GATE
0.3V
t
DIS
2.4V
V
EN
Figure 4. Disable Timing Diagram
MAX4881–MAX4884/MAX4893B
Overcurrent Flag Output (
FLAGI
)
The MAX4881–MAX4884/MAX4893B have an overcur-
rent-fault flag output (FLAGI) to indicate a current fault
condition. FLAGI asserts low to indicate a fault when the
current reaches the current limit for longer than the 50ms
blanking time. Toggle IN or CB or EN to release FLAGI
latched condition. FLAGI does not assert if the current-
limit fault occurs for less than the blanking time (Figure 5).
FLAGI is disabled when EN goes high. When CB is low,
the switch opens, but FLAGI is not active.
FLAGI is an open-drain active-low output. Connect a
pullup resistor from FLAGI to the logic I/O voltage of the
host system or to any voltage source up to 6V.
Current-Limit Switch
When the forward- or reverse-current-limit threshold is
exceeded, t
BLANK
timer begins counting. The timer
Overvoltage Protection Controllers with
Current Limit in TDFN
8 _______________________________________________________________________________________
LOAD
CURRENT
SWITCH
STATUS
OFF
CURRENT
LIMIT
ON
FLAGI
LOAD
CURRENT
SWITCH
STATUS
t
BLANK
t
BLANK
t
BLANK
t
BLANK
CURRENT
LIMIT
ON
(b) MAX4883C/MAX4884C
(a) MAX4881/MAX4882/MAX4883B/MAX4884B/MAX4893B
FLAGI
Figure 5. Current-Limit Fault Timing
LOAD
CURRENT
SWITCH
STATUS
t
BLANK
t
BLANK
OFF
ON
EN
STATUS
(a)
FLAGI
PIN STATUS
LOAD
CURRENT
SWITCH
STATUS
t
BLANK
t
BLANK
OFF
ON
(b)
FLAGI
CB
STATUS
(c)
UVLO
LOAD
CURRENT
SWITCH
STATUS
OFF
ON
FLAGI
t
BLANK
t
BLANK
STATUS
IN
STATUS
STATUS
Figure 6. Latchoff Fault Blanking (MAX4881/MAX4882/
MAX4883B/MAX4884B/MAX4893B
resets if the overcurrent condition disappears before
t
BLANK
has elapsed. The internal switch is latched off if
the overcurrent condition continues up to the end of the
blanking time (MAX4881/MAX4882/MAX4883B/
MAX4884B/MAX4893B). The MAX4883C/MAX4884C limit
the current infinitely until the thermal trip point occurs.
Reset the switch by toggling EN or CB or IN (Figure 6).
EN
Input
The MAX4881–MAX4884/MAX4893B feature an active-
low enable input (EN). Drive EN low or connect to
ground for normal operation. Drive EN high to force the
external n-channel MOSFET off, and to disable OV and
FLAGI.
GATE Driver
An on-chip charge pump drives the GATE voltage to
about twice above V
IN
, allowing the use of a low-cost
n-channel MOSFET (Figure 7). The actual GATE output
voltage tracks approximately 2 x V
IN
until V
IN
exceeds
the OVLO trip level, 5.6V (MAX4881/MAX4883/
MAX4893B) and 4.5V (MAX4882/MAX4884) typically.
The GATE output voltage, as a function of input volt-
age, is shown in the Typical Operating Characteristics.
Applications Information
MOSFET Selection
The MAX4881–MAX4884/MAX4893B are designed for
use with an n-channel MOSFET. MOSFETs with R
DS(ON)
,
specified for a V
GS
of 4.5V or less, work well. If the input
supply is near the UVLO minimum of 4.2V (MAX4881/
MAX4883/MAX4893B), or of 2.4V (MAX4882/ MAX4884),
consider using a MOSFET specified for a lower V
GS
volt-
age. Also, the V
DS
should be 30V for the MOSFET to
withstand the full 28V IN range of the MAX4881–
MAX4884/MAX4893B. Table 1 shows a selection of
MOSFETs appropriate for use with the MAX4881–
MAX4884/MAX4893B.
IN Bypass Considerations
Bypass IN to GND with a 1µF ceramic capacitor to
achieve 15kV ESD-protected input. When the power
source has significant inductance due to long lead
MAX4881–MAX4884/MAX4893B
Overvoltage Protection Controllers with
Current Limit in TDFN
_______________________________________________________________________________________ 9
IN
OVLO
UVLO
CHARGE PUMP
IN
OV
FLAGI
EN
CHARGE
PUMP
GND
1.1A/0.7A
LIMIT
I
REF
BTA
UVLO
BTA
BTB
CB
MAX4881/MAX4882
MAX4883B/MAX4884B
MAX4893B
BLANKING TIME
AND LATCHOFF LOGIC
GATE
Figure 7a. MAX4881/MAX4882/MAX4883B/MAX4884B/
MAX4893B Functional Diagram
IN
OVLO
UVLO
CHARGE PUMP
GATE
IN
OV
FLAGI
EN
CHARGE
PUMP
GND
1.1A/0.7A
LIMIT
I
REF
BTA
UVLO
BTA
BTB
CB
MAX4883C/MAX4884C
BLANKING TIME
LOGIC
Figure 7b. MAX4883C/MAX4884C Functional Diagram
P1-P3P4-P6P7-P9P10-P12P13-P13

MAX4893BETB+T

Mfr. #:
Buy MAX4893BETB+T
Manufacturer:
Maxim Integrated
Description:
Current & Power Monitors & Regulators Overvoltage Protect Controller
Lifecycle:
New from this manufacturer.
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