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MAX5948AESAMAXIMN/a10avai-48V Hot-Swap Controllers with External RSENSE
MAX5948BESAMAXIM ?N/a6avai-48V Hot-Swap Controllers with External RSENSE


MAX5948AESA ,-48V Hot-Swap Controllers with External RSENSEFeaturesThe MAX5948A/MAX5948B are hot-swap controllers♦ Allow Safe Board Insertion and Removal from ..
MAX5948AESA+ ,-48V Hot-Swap Controllers with External RSENSEApplicationsSelector GuideCentral-Office SwitchingNetwork Switches/Routers PART PWRGD POLARITYMAX59 ..
MAX5948BESA ,-48V Hot-Swap Controllers with External RSENSEELECTRICAL CHARACTERISTICS(V = 0V, V = 48V, T = -40°C to +85°C. Typical values are at T = +25°C, un ..
MAX5948BESA+ ,-48V Hot-Swap Controllers with External RSENSEFeaturesThe MAX5948A/MAX5948B are hot-swap controllers♦ Allow Safe Board Insertion and Removal from ..
MAX5949AESA ,-48V Hot-Swap Controllers with External RSENSEFeaturesThe MAX5949A/MAX5949B are hot-swap controllers that♦ Allow Safe Board Insertion and Removal ..
MAX5949AESA ,-48V Hot-Swap Controllers with External RSENSEApplicationsTelecom Line CardsPART TEMP RANGE PIN-PACKAGENetwork Switches/RoutersMAX5949AESA -40°C ..
MAZ8150-H ,Silicon planar typeZener DiodesMAZ8000 SeriesSilicon planar typeUnit : mmFor stabilization of power supplyKA
MAZ8150-L ,Silicon planar typeFeatures•Extremely low noise voltage caused from the diode (2.4V to 39V,1/3 to 1/10 of our conventi ..
MAZ8150-M ,Silicon planar typeAbsolute Maximum Ratings T = 25°CaMarking SymbolParameter Symbol Rating UnitRefer to the list of t ..
MAZ8160-H ,Silicon planar typeElectrical Characteristics T = 25°CaParameter Symbol Conditions Min Typ Max UnitForward voltage V ..
MAZ8160-L ,Silicon planar typeZener DiodesMAZ8000 SeriesSilicon planar typeUnit : mmFor stabilization of power supplyKA
MAZ8160-M ,Silicon planar typeelectrical characteristicsZ Zwithin part numbersReverse current I V ··············· Specified value ..


MAX5948AESA-MAX5948BESA
-48V Hot-Swap Controllers with External RSENSE
General Description
The MAX5948A/MAX5948B are hot-swap controllers
that allow a circuit card to be safely hot plugged into a
live backplane. The MAX5948A/MAX5948B operate
from -20V to -80V and are well-suited for -48V power
systems. The MAX5948A is pin- and function-compati-
ble with both the LT1640AL and LT1640L. The
MAX5948B is pin- and function-compatible with both
the LT1640AH and LT1640H.
The MAX5948A/MAX5948B provide a controlled turn-on
to circuit cards preventing glitches on the power-supply
rail and damage to board connectors and components.
The MAX5948A/MAX5948B provide undervoltage, over-
voltage, and overcurrent protection. These devices
ensure the input voltage is stable and within tolerance
before applying power to the load.
Both the MAX5948A and MAX5948B protect a system
against overcurrent and short-circuit conditions by turning
off the external MOSFET in the event of a fault condition.
Both devices feature an open-drain power-good status
output, PWRGDfor MAX5948A or PWRGD for
MAX5948B, that can be used to enable downstream
converters.
The MAX5948A/MAX5948B are available in an 8-pin SO
package. Both devices are specified for the extended
-40°C to +85°C temperature range.
Applications

Central-Office Switching
Network Switches/Routers
Server Line Cards
Base-Station Line Cards
Features
Allow Safe Board Insertion and Removal from a
Live -48V Backplane
Pin- and Function-Compatible with
LT1640AL/LT1640L (MAX5948A)
Pin- and Function-Compatible with
LT1640AH/LT1640H (MAX5948B)
Withstand -100V Input Transients with No
External Components
Operate from -20V to -80VProgrammable Inrush and Short-Circuit Current
Limits
Programmable Overvoltage ProtectionProgrammable Undervoltage LockoutPower Up into a Shorted LoadPower-Good Control Output
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE
Pin Configuration
Ordering Information

19-3473; Rev 0; 10/04
Typical Operating Circuit appears at end of data sheet.
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE
ABSOLUTE MAXIMUM RATINGS

Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
(All voltages are referenced to VEE, unless otherwise noted.)
Supply Voltage (VDD- VEE).................................-0.3V to +100V
PWRGD, PWRGD.................................................-0.3V to +100V
DRAIN (Note 1)........................................................-2V to +100V
SENSE....................................................................-0.3V to +20V
GATE (internally clamped).....................................-0.3V to +18V
UV and OV..............................................................-0.3V to +60V
Current through SENSE....................................................±20mA
Current into GATE...........................................................±300mA
Current into Any Other Pin................................................±20mA
Current into Drain............................................-100mA to +20mA
Continuous Power Dissipation (TA= +70°C)
8-Pin SO (derate 5.9mW/°C above +70°C)...................471mW
Operating Temperature Range...........................-40°C to +85°C
Junction Temperature .....................................................+150°C
Storage Temperature Range.............................-65°C to +150°C
Lead Temperature (soldering, 10s).................................+300°C
ELECTRICAL CHARACTERISTICS

(VEE= 0V, VDD= 48V, TA= -40°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.) (Notes 2, 3)
Note 1:
Test condition per Figure 1. DRAIN current must be limited to the specified 100mA maximum.
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE
ELECTRICAL CHARACTERISTICS (continued)

(VEE= 0V, VDD= 48V, TA= -40°C to +85°C. Typical values are at TA= +25°C, unless otherwise noted.) (Notes 2, 3)
Note 2:
All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to VEE,
unless otherwise specified.
Note 3:
Limits are 100% tested at TA= +25°C and +85°C. Limits at -40°C are guaranteed by design.
Figure 1. -2V DRAIN Voltage Test Circuit
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE
Typical Operating Characteristics

(VDD= 48V, VEE= 0V, TA= +25°C, unless otherwise noted.)
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE

Figure 2. Test Circuit 1
Typical Operating Characteristics (continued)

(VDD= 48V, VEE= 0V, TA= +25°C, unless otherwise noted.)
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE
Timing Diagrams

Figure 3. OV to GATE Timing
Figure 4. UV to GATE Timing
Figure 5. SENSE to GATE Timing
Figure 6. DRAIN to PWRGD/PWRGD Timing
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE
Detailed Description

The MAX5948A/MAX5948B are integrated hot-swap
controllers for -48V power systems. They allow circuit
boards to be safely hot plugged into a live backplane
without causing a glitch on the power-supply rail. When
circuit boards are inserted into a live backplane, the
bypass capacitors at the input of the board’s power
module or switching power supply can draw large
inrush currents as they charge. The inrush currents can
cause glitches on the system power-supply rail and
damage components on the board.
The MAX5948A/MAX5948B provide a controlled turn-on
to circuit cards preventing glitches on the power-sup-
ply rail and damage to board connectors and compo-
nents. Both the MAX5948A and MAX5948B provide
undervoltage, overvoltage, and overcurrent protection.
The MAX5948A/MAX5948B ensure the input voltage is
stable and within tolerance before applying power to
the load.
Board Insertion

Figure 6a shows a typical hot-swap circuit for -48V sys-
tems. When the circuit board first makes contact with the
backplane, the DRAIN to GATE capacitance (Cgd) of Q1
pulls up the GATE voltage to roughly I(VEEx Cgd) /
(Cgd+ Cgs)I. The MAX5948_ features an internal
dynamic clamp between GATE and VEEto keep the
gate-to-source voltage of Q1 low during hot insertion,
preventing Q1 from passing an uncontrolled current to
the load. For most applications, the internal clamp
between GATE and VEEof the MAX5948A/MAX5948B
eliminates the need for an external gate-to-source
capacitor. Resistor R3 limits the current into the clamp
circuitry during card insertion.
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE
Power-Supply Ramping

The MAX5948A/MAX5948B can reside either on the
backplane or the removable circuit board (Figure 6a).
Power is delivered to the load by placing an external
n-channel MOSFET pass transistor in the power-
supply path.
After the circuit board is inserted into the backplane and
the supply voltage at VEEis stable and within the under-
voltage and overvoltage tolerance, the MAX5948A/
MAX5948B turn on Q1. The MAX5948A/MAX5948B grad-
ually turn on the external MOSFET by charging the gate
of Q1 with a 45µA current source. Capacitor C2 provides
a feedback signal to accurately limit the inrush current.
The inrush current can be calculated:
IINRUSH= (IPUx CL) / C2
where CLis the total load capacitance, C3 + C4, and
IPUis the MAX5948_ gate pullup current.
Figure 6b shows the inrush current waveform. The cur-
rent through C2 controls the GATE voltage. At the end
of the DRAIN ramp, the GATE voltage is charged to its
final value. The GATE-to-SENSE clamp limits the maxi-
mum VGSto about 18V under any condition.
Board Removal

If the card is removed from a live backplane, the output
capacitor on the card may not be immediately dis-
charged. While the output capacitor is discharging, the
MAX5948_ continues to operate as if the input supply
were still connected because the output capacitor tem-
porarily supplies operating current to the IC. If the cir-
cuit is connected as in Figure 7a, the voltage at the UV
pin falls below the UVLO detect threshold, and the
MAX5948_ turns off the external MOSFET. If R4 in the
circuit is connected directly to the -48V return, the
external MOSFET remains on until the capacitor is dis-
charged sufficiently to drop the UV pin voltage to the
UVLO detect threshold.
In either case, when the MOSFET is turned off, the out-
put capacitor continues to discharge by the IC supply
current IDD. The IDDflows into the IC at the VDDtermi-
nal, out at the VEEterminal, and back to the capacitor
through the substrate diode of the external MOSFET.
There is also a parallel current path between the VEE
and DRAIN terminals through multiple internal ESD-pro-
tection diodes. The protection circuit built into the IC
allows the DRAIN terminal voltage to drop below that of
Block Diagram
MAX5948A/MAX5948B
-48V Hot-Swap Controllers
with External RSENSE

the VEEterminal so long as the absolute maximum
allowed DRAIN terminal current (-100mA) is not
exceeded. As IDDis only 2mA maximum, this limiting
current will not even be approached.
Electronic Circuit Breaker

The MAX5948 provides a circuit-breaker feature that
protects against excessive load current and short-cir-
cuit conditions. The load current is monitored by sens-
ing the voltage across an external sense resistor
connected between VEEand SENSE.
If the voltage between VEEand SENSE exceeds the
current-limit trip voltage (VCB) for a period of
tPHLSENSE, the electronic circuit breaker will trip, caus-
ing the MAX5948A/MAX5948B to turn off the external
MOSFET as shown in Figure 8.
After an overcurrent fault condition, the circuit breaker
can be reset by pulling the UV pin low and then pulling
UV high or by cycling power to the MAX5948A/
MAX5948B.
If more than 3µs (typ) deglitch time (tPHLSENSE) is
needed to prevent spurious shutdown due to load cur-
rent spikes or noise, a simple lowpass filter can be
used between the SENSE and VEEpins as shown in
Figure 7a. Inrush Control Circuitry
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