MAX8555 Datasheet, PDF (1/17 Pages) Maxim Integrated Products – Low-Cost, High-Reliability, 0.5V to 3.3V ORing MOSFET Controllers

13-3087; Rev 0; 1/04
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Low-Cost, High-Reliability, 0.5V to 3.3V ORing
MOSFET Controllers
General Description
Critical loads often employ parallel-connected power
supplies with redundancy to enhance system reliability.
The MAX8555/MAX8555A are highly integrated, inex-
pensive MOSFET controllers that provide isolation and
redundant power capability in high-reliability systems.
The MAX8555/MAX8555A are used in 0.5V to 3.3V sys-
tems, and have an internal charge pump to drive the
gates of the N-channel pass elements to (V_CS+ + 5V).
During startup, the MAX8555/MAX8555A monitor the
voltage drop across the external MOSFETs. Once V_CS+
approaches or exceeds the bus voltage (V_CS-), the
MOSFETs are turned on. The MAX8555/MAX8555A fea-
ture a dual-purpose TIMER input. A single external
resistor from TIMER to ground sets the turn-on speed of
the external MOSFETs. Optionally, the TIMER input can
be used as a logic enable input. Once the external
MOSFET is turned on, these controllers monitor the
load, protecting the bus against overvoltage, undervolt-
age, and reverse-current fault conditions. The
MAX8555 is available with a 40mV reverse-current
threshold, while the MAX8555A is available with a 20mV
reverse-current threshold.
Overvoltage and undervoltage fault thresholds are
adjustable and can be disabled. The current-limit trip
points are set by the external MOSFETs’ R_DS(ON),
reducing component count. An open-drain, logic-low
fault output indicates if an overvoltage, undervoltage, or
reverse-current fault occurs. The MAX8555 and the
MAX8555A can shut down in response to a reverse-
current fault condition as quickly as 200ns.
Both devices come in space-saving 10-pin µMAX or
TDFN packages and are specified over the extended
-40°C to +85°C temperature range.
Applications
Point-of-Load Supplies
Power-Supply Modules
Servers
Telecom Power Supplies
Rectifiers
Redundant Power Supplies in High-Availability
Systems
Typical Operating Circuit appears at end of data sheet.
Features
♦ Simple, Integrated, and Inexpensive MOSFET
Controllers
♦ ORing FET Drive for 0.5V to 3.3V
♦ Eliminate ORing Diode Power Dissipation
♦ Provide N+1 Redundant Supply Capability for
Highly Reliable Systems
♦ Isolate Failed Short-Circuit Supply from
Output BUS
♦ Respond to Reverse Short-Circuit Current
in 200ns
♦ Adjustable Blank Time
♦ Programmable Soft-Start
♦ Logic Enable Input
♦ Adjustable Overvoltage and Undervoltage
Trip Points
♦ Fault-Indicator Output
♦ Space-Saving Packages
Ordering Information
PART
MAX8555ETB
MAX8555EUB
MAX8555AETB
MAX8555AEUB
*Exposed paddle
TEMP
RANGE
PIN-
PACKAGE
TOP
MARK
-40°C to 85°C
10 TDFN
3mm x 3mm*
ACC
-40°C to 85°C
-40°C to 85°C
10 µMAX
10 TDFN
3mm x 3mm*
8555EUB
ADD
-40°C to 85°C 10 µMAX
8555AEUB
Pin Configurations
TOP VIEW
GATE 1
GND 2
VL 3
V_DD 4
UVP 5
MAX8555/
MAX8555A
µMAX
10 CS+ GATE 1
9 CS- GND 2
8 OVP
VL 3
7 FAULT V_DD 4
6 TIMER UVP 5
MAX8555/
MAX8555A
10 CS+
9 CS-
8 OVP
7 FAULT
6 TIMER
TDFN
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.