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PDF MAX5955 Data sheet ( Hoja de datos )
| Número de pieza | MAX5955 | |
| Descripción | Dual Hot-Swap Controllers | |
| Fabricantes | Maxim Integrated | |
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19-3813; Rev 0; 9/05
EVAALVUAAILTAIOBNLEKIT
Low-Voltage, Dual Hot-Swap
Controllers with Independent On/Off Control
General Description
The MAX5955 and MAX5956 are +1V to +13.2V dual
hot-swap controllers with independent on/off control for
complete protection of dual-supply systems. They allow
the safe insertion and removal of circuit cards into live
backplanes. The MAX5955 and MAX5956 operate
down to 1V provided one of the inputs is above 2.7V.
The discharged filter capacitors of the circuit card pro-
vide low impedance to the live backplane. High inrush
currents from the backplane to the circuit card can burn
up connectors and components, or momentarily collapse
the backplane power supply leading to a system reset.
The MAX5955 and MAX5956 hot-swap controllers pre-
vent such problems by gradually ramping up the output
voltage and regulating the current to a preset limit when
the board is plugged in, allowing the system to stabilize
safely. After the startup cycle is completed, two on-chip
comparators provide VariableSpeed/BiLevel™ protection
against short-circuit and overcurrent faults, as well as
immunity against system noise and load transients. In the
event of a fault condition, the load is disconnected. The
MAX5955B and MAX5956B must be unlatched after a
fault, and the MAX5955A and MAX5956A automatically
restart after a fault.
The MAX5955 and MAX5956 integrate an on-board
charge pump to drive the gates of low-cost, external n-
channel MOSFETs. The devices offer integrated fea-
tures like startup current regulation and current glitch
protection to eliminate external timing resistors and
capacitors. These devices provide open-drain status
outputs, an adjustable startup timer, and adjustable
current limits. The MAX5955 provides output undervolt-
age/overvoltage protection for each channel, while the
MAX5956 provides undervoltage/overvoltage monitor-
ing for each channel.
The MAX5955 and MAX5956 are available in a space-
saving 16-pin QSOP package.
Features
o Safe Hot Swap for +1V to +13.2V Power Supplies
with VIN1 or VIN2 ≥ 2.7V
o Independent On/Off Control for Each Channel
o Internal Charge Pumps Generate n-Channel
MOSFET Gate Drives
o Inrush Current Regulated at Startup
o Circuit-Breaker Function
o Adjustable Circuit Breaker/Current-Limit
Threshold from 25mV to 100mV
o VariableSpeed/BiLevel Circuit Breaker Response
o Autoretry or Latched Fault Management
o Status Outputs Indicate Fault/Safe Condition
o Output Undervoltage and Overvoltage Monitoring
or Protection
Ordering Information
PART
TEMP RANGE PIN-PACKAGE
MAX5955AEEE
-40°C to +85°C 16 QSOP
MAX5955AEEE+
-40°C to +85°C 16 QSOP
MAX5955AUEE
0°C to +85°C
16 QSOP
MAX5955AUEE+
0°C to +85°C
16 QSOP
MAX5955BEEE
-40°C to +85°C 16 QSOP
MAX5955BEEE+
-40°C to +85°C 16 QSOP
MAX5955BUEE
0°C to +85°C
16 QSOP
MAX5955BUEE+
0°C to +85°C
16 QSOP
+Denotes lead-free package.
Ordering Information continued at end of data sheet.
Selector Guide and Typical Operating Circuit appear at end
of data sheet.
Pin Configuration
Base Station Line Cards
Network Switches,
Routers, Hubs
Solid-State Circuit
Breakers
RAID
Applications
Power-Supply Sequencing
Hot Plug-In Daughter
Cards
Portable Computer Device
Bays (Docking Stations)
TOP VIEW
PGOOD1 1
TIM 2
IN1 3
SENSE1 4
GATE1 5
GND 6
LIM1 7
MON1 8
MAX5955
MAX5956
16 PGOOD2
15 ON2
14 IN2
13 SENSE2
12 GATE2
11 ON1
10 LIM2
9 MON2
Variable Speed/BiLevel is a trademark of Maxim Integrated
Products, Inc.
QSOP
________________________________________________________________ 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.
1 page  
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control
Typical Operating Characteristics (continued)
(Typical Operating Circuits, Q1 = Q2 = Fairchild FDB7090L, VIN1 = +5V, VIN2 = +3.3V, VON1 = VON2 = +2.7V, TA = +25°C, unless
otherwise noted. Channels 1 and 2 are identical in performance. Where characteristics are interchangeable, channels 1 and 2 are
referred to as X and Y.)
TURN-OFF TIME vs. SENSE VOLTAGE
(EXPANDED SCALE)
10
SLOW-COMPARATOR THRESHOLD
vs. RLIM
120
STARTUP PERIOD vs. RTIM
60
100 50
SLOW-COMP. THRESHOLD
1
80
60
40
40
30
20
20 10
0.1
20 25 30 35 40 45 50 55 60 65 70 75 80
VIN - VSENSE (mV)
TURN-OFF TIME
SLOW-COMPARATOR FAULT
MAX5955/56 toc13
0
0
0 tSCD
0
26mV STEP
0
VPGOOD
5V/div
0
0
VSENSE - VIN
100mV/div
VGATE
5V/div
0
100 200 300
RLIM (kΩ)
400
TURN-OFF TIME
FAST-COMPARATOR FAULT
MAX5955/56 toc14
0
0
tFCD
125mV STEP
VPGOOD
5V/div
VSENSE - VIN
100mV/div
VGATE
5V/div
100 200 300 400 500 600
RTIM (kΩ)
STARTUP WAVEFORMS
FAST TURN-ON
MAX5955/56 toc15
VON
2V/div
VPGOOD
2V/div
IOUT
5A/div
VOUT
5V/div
VGATE
5V/div
1ms/div
VIN = 5.0V
STARTUP WAVEFORMS
SLOW TURN-ON
MAX5955/56 toc16
VON
2V/div
VPGOOD
2V/div
IOUT
5A/div
VOUT
5V/div
VGATE
5V/div
400ns/div
VIN = 5.0V
1ms/div
VIN = 5.0V, RSENSE = 10mΩ,
RTIM = 27kΩ, CBOARD = 1000µF
AUTORETRY DELAY
MAX5955/56 toc17
VGATE
5V/div
VOUT
5V/div
IOUT
5A/div
1ms/div
VIN = 5.0V, RSENSE = 10mΩ, RTIM = 47kΩ,
CBOARD = 1000µF, CGATE = 22nF
40ms/div
VIN = 5.0V, RSENSE = 10mΩ, RTIM = 47kΩ,
CBOARD = 1000µF, RBOARD = 1.4Ω
_______________________________________________________________________________________ 5
5 Page 
Low-Voltage, Dual Hot-Swap Controllers with
Independent On/Off Control
Table 3. Component Manufacturers
COMPONENT
Sense Resistors
MOSFETs
MANUFACTURER
Dale-Vishay
IRC
Fairchild
International Rectifier
Motorola
Setting the Startup Period, RTIM
The startup period (tSTART) is adjustable from 0.45ms to
50ms. The adjustable startup period feature allows sys-
tems to be customized for MOSFET gate capacitance
and board capacitance (CBOARD). The startup period is
adjusted with the resistance connected from TIM to GND
(RTIM). RTIM must be between 4kΩ and 500kΩ. The
startup period has a default value of 9ms when TIM is left
floating. Calculate RTIM with the following equation:
RTIM
=
tSTART
128 × 800pF
where tSTART is the desired startup period.
Startup Sequence
There are two ways of completing the startup sequence.
Case A describes a startup sequence that slowly turns
on the MOSFETs by limiting the gate charge. Case B
uses the current-limiting feature and turns on the
MOSFETs as fast as possible while still preventing a high
inrush current. The output voltage ramp-up time (tON) is
determined by the longer of the two timings, case A and
case B. Set the startup timer tSTART to be longer than tON
to guarantee enough time for the output voltage to settle.
Case A: Slow Turn-On (Without Current Limit)
There are two ways to turn on the MOSFETs without
reaching the fast-comparator current limit:
• If the board capacitance (CBOARD) is small, the
inrush current is low.
• If the gate capacitance is high, the MOSFETs turn
on slowly.
In both cases, the turn-on time is determined only by the
charge required to enhance the MOSFET. The small
gate-charging current of 100µA effectively limits the out-
put voltage dV/dt. Connecting an external capacitor
between GATE and GND extends turn-on time. The time
required to charge/discharge a MOSFET is as follows:
PHONE
402-564-3131
704-264-8861
888-522-5372
310-233-3331
602-244-3576
WEBSITE
www.vishay.com
www.irctt.com
www.fairchildsemi.com
www.irf.com
www.mot-sps.com/ppd
where:
CGATE is the external gate to ground capacitance
(Figure 4).
∆VGATE is the change in gate voltage.
QGATE is the MOSFET total gate charge.
IGATE is the gate-charging/discharging current.
In this case, the inrush current depends on the MOSFET
gate-to-drain capacitance (Crss) plus any additional
capacitance from GATE to GND (CGATE), and on any
load current (ILOAD) present during the startup period.
IINRUSH
=
CBOARD
Crss + CGATE
×
IGATE +
ILOAD
Example: Charging and Discharging Times Using
the Fairchild FDB7030L MOSFET
If VIN1 = 5V then GATE1 charges up to 10.4V (VIN1 +
VDRIVE); therefore ∆VGATE = 10.4V. The manufacturer’s
data sheet specifies that the FDB7030L has approxi-
mately 60nC of gate charge and Crss = 600pF. The
MAX5955/MAX5956 have a 100µA gate-charging cur-
rent and a 3mA strong discharging current.
VIN
RPULLUP
*
RSENSE
0.1µF
IN_
PGOOD_
ON_
SENSE GATE
MAX5955
MAX5956
GND
VOUT
CBOARD
CGATE
t = CGATE × ∆VGATE + QGATE
IGATE
* REQUIRED COMPONENTS. SEE THE ON_ COMPARATORS SECTION.
Figure 4. Operating with an External Gate Capacitor
______________________________________________________________________________________ 11
11 Page | ||
| Páginas | Total 15 Páginas | |
| PDF Descargar | [ Datasheet MAX5955.PDF ] | |
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