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PDF MAX5977B Data sheet ( Hoja de datos )
| Número de pieza | MAX5977B | |
| Descripción | 1V to 16V / Single-Channel Hot-Swap Controllers | |
| Fabricantes | Maxim Integrated Products | |
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19-5553; Rev 1; 1/11
EVAALVUAAILTAIOBNLEKIT
1V to 16V, Single-Channel, Hot-Swap Controllers
with Precision Current-Sensing Output
General Description
The MAX5977A/MAX5977B hot-swap controllers provide
complete protection for systems with a 1V to 16V single-
supply voltage.
During the initial insertion, the hot-swap controllers
limit the inrush current from damaging the board or
from shorting out the backplane. When the input volt-
age is above the undervoltage threshold and below the
overvoltage threshold, a 5FA current source powered
from the internal 5V charge pump drives the gate of an
external n-channel MOSFET, providing a slow turn-on
response. An internal current-sense amplifier in the IC
monitors the current across an external shunt resistor,
providing current sensing for wide input-sense voltage
range. The devices provide two levels of overcurrent
circuit-breaker protections: a fast-trip threshold for a fast
turn-off and a lower slow-trip threshold for a delayed
turn-off.
Exceeding either of the overcurrent circuit-breaker
thresholds forces the device into fault mode where the
external n-channel MOSFET is disabled. The MAX5977
is available in two versions that provide a latched-off
(MAX5977A) or autoretry (MAX5977B) output when the
device is in fault mode.
A calibration mode allows further calibration of the inte-
grated transconductance amplifier for production testing
of the final design. The devices are offered in a 20-pin,
4mm x 4mm, TQFN-EP package and are fully specified
from -40NC to +85NC.
VariableSpeed/BiLevel is a trademark of Maxim Integrated
Products, Inc.
Features
S 1% Accurate Current-Sense Amplifier Output
S Hot-Swap Monitors Operation from 1V to 16V
S Integrated Charge Pump Fully Enhances the
External n-Channel FET (VGATE = VIN + 5V)
S VariableSpeed/BiLevelK Fault Protection Provides
Electronic Circuit-Breaker Function
S Output Latched Off After Fault Condition
(MAX5977A)
S Autoretry After Fault Condition (MAX5977B)
S Power-Good Indicator
S Calibration Mode
S Small, 20-Pin, 4mm x 4mm TQFN-EP Package
Applications
Servers
Storage Systems
Network Switches and Routers
General Hot-Swap
Ordering Information
PART
MAX5977AETP+
PIN-PACKAGE FAULT RESPONSE
20 TQFN-EP*
Latched
MAX5977BETP+ 20 TQFN-EP*
Autoretry
Note: All devices are specified over the -40NC to +85NC oper-
ating temperature range.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
Typical Operating Circuit
www.DataSheet4U.com
VIN
1V TO 16V
RSENSE
RCAL
RSCOMP RFCOMP
SCOMP FCOMP
IN
CALSENSE
RGATE
SENSE GATE
SOURCE
CSOUT
CGATE
TO LOAD
CL
CURRENT-SENSE
AMPLIFIER OUTPUT
RCSOUT
CALIBRATION
MODE INPUT
CAL
2.7V TO 16V
MAX5977A
MAX5977B
+3.3V
PWR
AGND GND
FAULT
PG
FAULT OUTPUT
POWER-GOOD OUTPUT
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
1 page  
1V to 16V, Single-Channel, Hot-Swap Controllers
with Precision Current-Sensing Output
Typical Operating Characteristics (continued)
(VPWR = VIN = 3.3V, TA = +25NC, RFCOMP = RSCOMP = 2kI, RGATE = 1kI, CGATE = 330nF, CREG = 1FF, unless otherwise noted.)
55
50
45
40
35
30
25
20
15
10
5
0
-50
1.0
0.8
0.6
0.4
0.2
0
-0.2
-0.4
-0.6
-0.8
-1.0
0
I_COMP vs. TEMPERATURE
IFCOMP
ISCOMP
-25 0 25 50 75 100
TEMPERATURE (°C)
CURRENT OUTPUT ERROR
vs. VIN - VSENSE
VIN = VPWR = 12V
RCSOUT = 10kI
10 20 30 40
VIN - VSENSE (mV)
50
SLOW-COMPARATOR RESPONSE TIME
(50mV OVERDRIVE)
MAX5997 toc08
VIN - VSENSE
50mV/div
0V
www.DataSheet4U.com
RSENSE = 4mI
100µs/div
VGATE
5V/div
0V
VSOURCE
2V/div
0V
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
4.80
4.75
0
VGATE vs. VIN
5 10 15
VIN (V)
20
tSCD vs. OVERDRIVE VOLTAGE
1000
100
0
5 10 15 20 25 30 35 40 45 50
OVERDRIVE VOLTAGE (mV)
SLOW-COMPARATOR RESPONSE TIME
(50mV OVERDRIVE)
MAX5977 toc09
VIN - VSENSE
100mV/div
0V
RSENSE = 4mI
20µs/div
VGATE
5V/div
0V
VSOURCE
2V/div
0V
5
5 Page 
1V to 16V, Single-Channel, Hot-Swap Controllers
with Precision Current-Sensing Output
An output resistor, RCSOUT, must be connected between
the transconductance current-sense amplifier output
CSOUT and AGND. The transconductance GM, of the
amplifier is typically 2500FS:
RCSOUT × GM × VSENSE, FS ≤ 2.5V
n-Channel MOSFET Selection
Select the external n-channel MOSFET according to the
application’s current level. The MOSFET’s on-resistance
(RDS(ON)) should be chosen low enough to have a mini-
mum voltage drop at full load to limit the MOSFET power
dissipation. High RDS(ON) causes output ripple if there
is a pulsating load. Determine the device power rating to
accommodate a short-circuit condition on the board at
startup and when the device is in automatic-retry mode
(see the MOSFET Thermal Considerations section).
The MAX5977A’s fault latch allows the use of MOSFETs
with lower power ratings. A MOSFET typically withstands
single-shot pulses with higher dissipation than the speci-
fied package rating.
MOSFET Thermal Considerations
During normal operation, the external MOSFETs dis-
sipate little power. The MOSFET RDS(ON) is low when
the MOSFET is fully enhanced. The power dissipated in
normal operation is PD = ILOAD2 x RDS(ON). The most
power dissipation occurs during the turn-on and turn-off
transients when the MOSFETs are in their linear regions.
Take into consideration the worst-case scenario of a
continuous short-circuit fault; consider these two cases:
1) The single turn-on with the device latched after a fault
(MAX5977A).
2) The continuous automatic retry after a fault
(MAX5977B).
MOSFET manufacturers typically include the package
thermal resistance from junction to ambient (RBJA) and
thermal resistance from junction to case (RBJC), which
determine the startup time and the retry duty cycle
(d = tSU/(tSU + tRETRY)). Calculate the required transient
thermal resistance with the following equation:
Z θJA(MAX)
≤
TJMAX × TA
VIN × IINRUSH
Layout Considerations
To take full advantage of the switch response time to an
output fault condition, it is important to keep all traces
as short as possible and to maximize the high-current
trace dimensions to reduce the effect of undesirable
parasitic resistance and inductance. Place the devices
close to the card’s connector, and a 0.01FF capacitor to
GND should be placed as close as possible to VIN. Use
a ground plane to minimize impedance and inductance.
Minimize the current-sense resistor trace length and
ensure accurate current sensing with Kelvin connec-
tions.
When the output is short circuited, the voltage drop
across the external MOSFET becomes large. Hence, the
power dissipation across the switch increases, as does
the die temperature. An efficient way to achieve good
power dissipation on a surface-mount package is to lay
out two copper pads directly under the MOSFET pack-
age on both sides of the board. Connect the two pads to
the ground plane through vias, and use enlarged copper
mounting pads on the top side of the board.
Related Parts
PART
MAX5970
MAX5978
DESCRIPTION
0 to 16V, Dual Hot-Swap Controller with
a 10-Bit Current and Voltage Monitor and
Four LED Drivers
0 to 16V, Single Hot-Swap Controller with
a 10-Bit Current and Voltage Monitor Plus
Four LED Drivers
www.DataSheet4U.com
11
11 Page | ||
| Páginas | Total 13 Páginas | |
| PDF Descargar | [ Datasheet MAX5977B.PDF ] | |
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