MAXIM MAX5925CEUB

KIT
ATION
EVALU
E
L
B
A
IL
AVA
19-3443; Rev 3; 4/10
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
The MAX5924/MAX5925/MAX5926 1V to 13.2V hot-swap
controllers allow the safe insertion and removal of circuit
cards into live backplanes. These devices hot swap supplies ranging from 1V to 13.2V provided that the device
supply voltage, VCC, is at or above 2.25V and the hotswapped supply, VS, does not exceed VCC.
The MAX5924/MAX5925/MAX5926 hot-swap controllers
limit the inrush current to the load and provide a circuitbreaker function for overcurrent protection. The devices
operate with or without a sense resistor. When operating without a sense resistor, load-probing circuitry
ensures a short circuit is not present during startup,
then gradually turns on the external MOSFET. After the
load probing is complete, on-chip comparators provide
overcurrent protection by monitoring the voltage drop
across the external MOSFET on-resistance. In the event
of a fault condition, the load is disconnected.
The MAX5924/MAX5925/MAX5926 include many integrated features that reduce component count and
design time, including configurable turn-on voltage,
slew rate, and circuit-breaker threshold. An on-board
charge pump provides the gate drive for a low-cost,
external n-channel MOSFET.
The MAX5924/MAX5925/MAX5926 are available with
open-drain PGOOD and/or PGOOD outputs. The
MAX5925/MAX5926 also feature a circuit breaker with
temperature-compensated R DS(ON) sensing. The
MAX5926 features a selectable 0ppm/°C or 3300ppm/°C
temperature coefficient. The MAX5924 temperature coefficient is 0ppm/°C and the MAX5925 temperature coefficient is 3300ppm/°C. Autoretry and latched faultmanagement configurations are available (see the
Selector Guide).
Features
o
o
o
o
o
o
o
o
o
o
Hot Swap 1V to 13.2V with VCC ≥ 2.25V
Drive High-Side n-Channel MOSFET
Operation With or Without RSENSE
Temperature-Compensated RDS(ON) Sensing
Protected During Turn-On into Shorted Load
Adjustable Circuit-Breaker Threshold
Programmable Slew-Rate Control
Programmable Turn-On Voltage
Autoretry or Latched Fault Management
10-Pin µMAX® or 16-Pin QSOP Packages
Ordering Information
PART
MAX5924AEUB
TEMP RANGE
PIN-PACKAGE
-40°C to +85°C
10 µMAX
MAX5924BEUB
-40°C to +85°C
10 µMAX
MAX5924CEUB*
-40°C to +85°C
10 µMAX
MAX5924DEUB*
-40°C to +85°C
10 µMAX
MAX5925AEUB
-40°C to +85°C
10 µMAX
MAX5925BEUB*
-40°C to +85°C
10 µMAX
MAX5925CEUB*
-40°C to +85°C
10 µMAX
MAX5925DEUB*
-40°C to +85°C
10 µMAX
MAX5926EEE
-40°C to +85°C
16 QSOP–EP**
*Future product—contact factory for availability.
**EP = Exposed pad.
Typical Operating Circuits
TYPICAL OPERATION WITHOUT RSENSE
Applications
Base Stations
RAID
BACKPLANE
VS
VCC
REMOVABLE CARD
N
1V TO VCC
VOUT
2.25V TO 13.2V
RCB
Remote-Access Servers
Network Routers and Switches
RSC
CB
Servers
GATE SENSE OUT
SC_DET
VCC
Portable Device Bays
GND
GND
MAX5925
MAX5926
µMAX is a registered trademark of Maxim Integrated Products, Inc.
SEE FIGURE 1 FOR A DETAILED TYPICAL OPERATING CIRCUIT WITHOUT RSENSE.
Selector Guide appears at end of data sheet.
Pin Configurations appear at end of data sheet.
Typical Operating Circuits continued at end of data sheet.
________________________________________________________________ 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.
MAX5924/MAX5925/MAX5926
General Description
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
VCC .........................................................................-0.3V to +14V
GATE*.....................................................................-0.3V to +20V
All Other Pins ............-0.3V to the lower of (VCC + 0.3V) or +14V
SC_DET Current (200ms pulse width, 15% duty cycle) ...140mA
Continuous Current (all other pins) .....................................20mA
Continuous Power Dissipation (TA = +70°C)
10-Pin µMAX (derate 6.9mW/°C above +70°C) ...........556mW
16-Pin QSOP (derate 18.9mW/°C above +70°C).......1509mW
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
Soldering Temperature (reflow) .......................................+260°C
*GATE is internally driven and clamped. Do not drive GATE with external source.
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.
ELECTRICAL CHARACTERISTICS
(VCC, EN (MAX5924/MAX5925), EN1 (MAX5926) = +2.7V to +13.2V; EN2 (MAX5926) = 0V; VS (see Figure 1) = +1.05V to VCC;
TA = -40°C to +85°C, unless otherwise noted. Typical values are at VCC = 5V, RL = 500Ω from OUT to GND, CL = 1µF, SLEW =
open, TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
13.2
V
POWER SUPPLIES
VCC Operating Range
VCC
2.7
VS Operating Range
VS
VS as defined in Figure 1
Supply Current
ICC
FET is fully enhanced, SC_DET = VCC
1.0
VCC
V
1.5
2.5
mA
2.06
2.47
UNDERVOLTAGE LOCKOUT (UVLO)
UVLO Threshold
VUVLO
VCC UVLO Deglitch Time
tDG
VCC UVLO Startup Delay
tD,UVLO
Default value, VS and VCC increasing, Figure 1
1.73
(Note 2)
900
V
µs
123
200
350
ms
2.7V < VCC < 5V
4
30
65
5V < VCC < 13.2V
3
10
20
43
102
205
ms
172
200
235
mV
LOAD-PROBE
Load-Probe Resistance (Note 3)
Load-Probe Timeout
Load-Probe Threshold Voltage
RLP
tLP
VLP,TH
(Note 4)
Ω
CIRCUIT BREAKER
ICB
Circuit-Breaker Programming
Current
ICB25
ICB85
2
VCC = 2.7V and VCB
TC = high
= 1V
(MAX5926), MAX5924
2.7V ≤ VCC ≤ 13.2V
TC = low (MAX5926),
MAX5925 (Note 5)
TC = low (MAX5926),
MAX5925 (Note 5)
37
34
37
42
VCC = 2.7V, VCB =
1V, TA = +25°C
30
40
50
2.7V ≤ VCC ≤ 13.2V,
TA = +25°C
40
50
60
VCC = 2.7V and VCB
= 1V, TA = +85°C
40
50
60
2.7V ≤ VCC ≤ 13.2V,
TA = +85°C
50
60
70
µA
_______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
(VCC, EN (MAX5924/MAX5925), EN1 (MAX5926) = +2.7V to +13.2V; EN2 (MAX5926) = 0V; VS (see Figure 1) = +1.05V to VCC;
TA = -40°C to +85°C, unless otherwise noted. Typical values are at VCC = 5V, RL = 500Ω from OUT to GND, CL = 1µF, SLEW =
open, TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
Circuit-Breaker Programming
Current During Startup
ICB,SU
Circuit-Breaker Enable Threshold
VCB,EN
Circuit-Breaker Comparator Offset
Voltage
VCB_OS
CONDITIONS
MIN
TYP
MAX
2 x ICB
VGATE - VOUT, rising gate voltage (Note 6)
2.3
UNITS
µA
3.6
4.65
V
0.3
±4.7
mV
Fast Circuit-Breaker Offset
Resistor
RCBF
Figure 3
1.2
1.9
2.7
kΩ
Slow Circuit-Breaker Delay
tCBS
VCB - VSENSE = 10mV
0.95
1.6
2.95
ms
Fast Circuit-Breaker Delay
tCBF
VCB - VSENSE = 500mV
Circuit-Breaker Trip Gate
Pulldown Current
IGATE,PD
Circuit-Breaker Temperature
Coefficient
OUT Current
TCICB
VGATE = 2.5V, VCC = 13.2V
13.5
280
ns
27
mA
MAX5924, TC = high (MAX5926)
0
MAX5925, TC = low (MAX5926)
3300
IOUT
ppm/°C
120
µA
7.2
V
MOSFET DRIVER
External Gate Drive
VGS
Load Voltage Slew Rate
Gate Pullup Current Capacity
SR
IGATE
VGATE - VOUT
2.7V ≤ VCC ≤ 13.2V
SLEW = open, CGATE = 10nF
4.2
5.5
2.19
9.5
CSLEW = 300nF, CGATE = 10nF (Note 8)
VGATE = 0V
V/ms
0.84
239
µA
ENABLE COMPARATOR
EN, EN1 Reference Threshold
EN, EN1 Hysteresis
VEN/UVLO
VEN (MAX5924/MAX5925) or
VEN1 (MAX5926) rising
0.747
VEN,HYS
0.795
0.850
30
V
mV
IEN
EN (MAX5924/MAX5925) = VCC,
EN1 (MAX5926) = VCC
±8
±50
nA
Power-Good Output Low Voltage
VOL
IOL = 1mA
0.3
0.4
V
Power-Good Output Open-Drain
Leakage Current
IOH
PGOOD/PGOOD = 13.2V
0.2
1
µA
3.6
4.7
EN, EN1 Input Bias Current
DIGITAL OUTPUTS (PGOOD, PGOOD)
Power-Good Trip Point
Power-Good Hysteresis
VTHPGOOD VGATE - VOUT, rising gate voltage
VPG,HYS
VCB_EN
0.36
V
V
_______________________________________________________________________________________
3
MAX5924/MAX5925/MAX5926
ELECTRICAL CHARACTERISTICS (continued)
ELECTRICAL CHARACTERISTICS (continued)
(VCC, EN (MAX5924/MAX5925), EN1 (MAX5926) = +2.7V to +13.2V; EN2 (MAX5926) = 0V; VS (see Figure 1) = +1.05V to VCC;
TA = -40°C to +85°C, unless otherwise noted. Typical values are at VCC = 5V, RL = 500Ω from OUT to GND, CL = 1µF, SLEW =
open, TA = +25°C, unless otherwise noted.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
0.6
1.6
3.3
s
LOGIC AND TIMING (TC, LATCH (MAX5926), EN2 (MAX5926)
Autoretry Delay
tRETRY
Autoretry mode
VIH
Input Voltage
2.0
V
0.4
VIL
Input Bias Current
IBIAS
Logic high at 13.2V
Time to Clear a Latched Fault
TCLR
MAX5924A/MAX5924B
MAX5925A/MAX5925B
MAX5926 in latched mode
3
µA
200
µS
All devices are 100% tested at TA = +25°C and +85°C. All temperature limits at -40°C are guaranteed by design.
VCC drops 30% below the undervoltage lockout voltage during tDG are ignored.
RLP is the resistance measured between VCC and SC_DET during the load-probing phase, tLP.
Tested at +25°C & +85°C. Guaranteed by design at -40°C.
The circuit-breaker programming current increases linearly from VCC = 2.25V to 5V. See the Circuit-Breaker Current vs.
Supply Voltage graph in the Typical Operating Characteristics.
Note 6: See the Startup Mode section for more information.
Note 7: VGATE is clamped to 17V (typ) above ground.
Note 8: dv/dt = 330 x 10-9/CSLEW (V/ms), nMOS device used for measurement was IRF9530N. Slew rate is measured at the load.
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Typical Operating Characteristics
(VCC = 5V, CL = 1µF, CSLEW = 330nF, CGATE = 10nF, RL = 500Ω, Figure 1, TA = +25°C, unless otherwise noted.)
MAX5926 SUPPLY CURRENT
vs. TEMPERATURE
ENABLED
2.4
1.6
VCC = VS
2.0
6
VCC = 13.2V
DISABLED
VCC = 5.0V
1.2
VCC = 3.0V
0.8
0.8
0.4
VGATE - VS (V)
1.2
ICC (mA)
1.6
4
6
8
VCC (V)
10
12
14
VS = 1V
VS = 3V
4
VS = VCC
VS = 5V
3
0
2
5
VCC = 2.25V
0.4
0
4
7
MAX5924 toc02
VCC = VS
MAX5924 toc01
2.0
GATE-DRIVE VOLTAGE
vs. SUPPLY VOLTAGE
MAX5924 toc03
MAX5926 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
ICC (mA)
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
2
-40
-15
10
35
TEMPERATURE (°C)
60
85
2
4
6
8
VCC (V)
_______________________________________________________________________________________
10
12
14
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
CIRCUIT-BREAKER CURRENT
vs. SUPPLY VOLTAGE (TC = 3300ppm/°C)
CIRCUIT-BREAKER CURRENT
vs. HOT-SWAP VOLTAGE
VCC = VS
5.5
TC = 3300ppm/°C
52
VCC = 5.0V
55
MAX5924 toc05
56
MAX5924 toc04
6.0
MAX5924 toc06
GATE DRIVE VOLTAGE
vs. TEMPERATURE
VCC = VS
53
VCC = 3.0V
4.5
48
ICB (µA)
CB (µ )
VGS (V)
5.0
51
44
VCC = 13.2V
3.0
VCC = 13.2V
36
10
35
TEMPERATURE (°C)
60
85
0
2
6
8
10
12
47
2
14
4
6
CIRCUIT-BREAKER PROGRAMMING
CURRENT vs. TEMPERATURE
80
MAX5924 toc07
VCC = VS
39.2
VCC = VS = 5V
70
39.0
ICB (µA)
38.6
10
12
14
SLEW RATE vs. CSLEW
60
38.8
8
VCC (V)
VS (V)
CIRCUIT-BREAKER CURRENT
vs. SUPPLY VOLTAGE (TC = 0ppm/°C)
39.4
4
100
SLEW RATE (V/ms)
-15
MAX5924 toc08
-40
ICB (µA)
49
TC = 0ppm/°C
40
3.5
TC = 3300ppm/°C
50
40
MAX5924 toc09
4.0
10
1
TC = 0ppm/°C
38.4
30
38.2
20
2
4
6
8
VCC (V)
10
12
14
0.1
-40
-15
10
35
TEMPERATURE (°C)
60
85
0
500
1000
1500
2000
CSLEW (nF)
_______________________________________________________________________________________
5
MAX5924/MAX5925/MAX5926
Typical Operating Characteristics (continued)
(VCC = 5V, CL = 1µF, CSLEW = 330nF, CGATE = 10nF, RL = 500Ω, Figure 1, TA = +25°C, unless otherwise noted.)
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Typical Operating Characteristics (continued)
(VCC = 5V, CL = 1µF, CSLEW = 330nF, CGATE = 10nF, RL = 500Ω, Figure 1, TA = +25°C, unless otherwise noted.)
TURN-ON WAVEFORM
(CSLEW = OPEN)
TURN-ON WAVEFORM
(CSLEW = 330nF)
MAX5924 toc10
GATE
5V/div
MAX5924 toc11
GATE
5V/div
0V
0V
OUT
5V/div
0V
OUT
5V/div
0V
PGOOD
5V/div
0V
PGOOD
5V/div
0V
200µs/div
2ms/div
TURN-OFF WAVEFORM
OVERCURRENT CIRCUIT-BREAKER EVENT
MAX5924 toc12
MAX5924 toc13
1A/div
EN1
5V/div
0V
IFET
0A
tCBS
GATE
10V/div
5V/div
GATE
0V
10V/div
0V
0V
OUT
PGOOD
5V/div
0V
5V/div
PGOOD
0V
400µs/div
2µs/div
SHORT-CIRCUIT CIRCUIT-BREAKER EVENT
AUTORETRY DELAY
MAX5924 toc14
IFET
MAX5924 toc15
1A/div
EN1
5V/div
0V
tD,UVLO
0A
GATE
5V/div
OUT
0V
5V/div
0V
tRETRY
5V/div
SC_DET
0V
OUT
100mV/div
5V/div
0V
PGOOD
0V
2µs/div
6
400ms/div
_______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
OVERCURRENT FAULT AND
AUTORETRY DELAY
UVLO DELAY AND LOAD PROBING
MAX5924 toc16
EN1
GATE
SC_DET
MAX5924 toc17
5V/div
0V
5V/div
0V
EN1
5V/div
SC_DET
5V/div
0V
tD,UVLO
tLP
5V/div
0V
OUT
200mV/div
0V
OUT
100mV/div
0V
0V
400ms/div
40ms/div
UVLO RESPONSE
UVLO DEGLITCH RESPONSE
MAX5924 toc18
MAX5924 toc19
>tDG
2V/div
GATE
GATE
2V/div
<tDG
0V
0V
1V/div
1V/div
VCC
VCC
0V
200µs/div
0V
200µs/div
_______________________________________________________________________________________
7
MAX5924/MAX5925/MAX5926
Typical Operating Characteristics (continued)
(VCC = 5V, CL = 1µF, CSLEW = 330nF, CGATE = 10nF, RL = 500Ω, Figure 1, TA = +25°C, unless otherwise noted.)
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
MAX5924/MAX5925/MAX5926
Pin Description
PIN
MAX5924A/ MAX5924B/
MAX5924C/ MAX5924D/
MAX5926
MAX5925A/ MAX5925B/
MAX5925C MAX5925D
1
8
1
1
NAME
VCC
FUNCTION
Power-Supply Input. Connect VCC to a voltage between 2.47V and 13.2V.
VCC must always be equal to or greater than VS (see Figure 1).
2
2
2
SC_DET
Short-Circuit Detection Output. Connect SC_DET to VOUT through a series
resistor, RSC, when not using RSENSE. SC_DET forces current (limited to
≈200mA) into the external load through RSC at startup to determine whether
there is a short circuit (load probing). Connect SC_DET directly to VCC when
using RSENSE, Do not connect SC_DET to VCC when not using RSENSE in an
attempt to disable load probing.
3
3
—
EN
ON/OFF Control Input. Drive EN high to enable the device. Drive EN low to
disable the device. An optional external resistive-divider connected between
VCC, EN, and GND sets the programmable turn-on voltage.
4
—
4
PGOOD
Open-Drain Active-Low Power-Good Output
—
4
7
PGOOD
Open-Drain Active-High Power-Good Output
5
5
5
GND
Ground
6
6
12
SLEW
Slew-Rate Adjustment Input. Connect an external capacitor between SLEW and
GND to adjust the gate slew rate. Leave SLEW unconnected for the default
slew rate.
7
7
13
GATE
Gate-Drive Output. Connect GATE to the gate of the external n-channel
MOSFET.
8
8
14
OUT
Output Voltage. Connect OUT to the source of the external MOSFET.
9
9
15
SENSE
10
10
16
CB
Circuit-Breaker Threshold Programming Input. Connect an external resistor,
RCB, from CB to VS to set the circuit-breaker threshold voltage.
Circuit-Breaker Sense Input. Connect SENSE to OUT when not using an
external RSENSE (Figure 1). Connect SENSE to the drain of the external
MOSFET when using an external RSENSE (Figure 2).
—
—
3
EN1
Active-High ON/OFF Control Input. Drive EN1 high to enable the device when
EN2 is low. Drive EN1 low to disable the device, regardless of the state of EN2.
An optional external resistive-divider between VCC, EN1, and GND sets the
programmable turn-on voltage while EN2 is low.
—
—
6
EN2
Active-Low ON/OFF Control Input. Drive EN2 low to enable the device when
EN1 is high. Drive EN2 high to disable the device, regardless of the state of
EN1.
—
—
8
LATCH
Latch Mode Input. Drive LATCH low for autoretry mode. Drive LATCH high for
latched mode.
—
—
9
TC
Circuit-Breaker Temperature Coefficient Selection Input. Drive TC low to select
a 3300ppm/°C temperature coefficient. Drive TC high to select a 0ppm/°C
temperature coefficient.
—
—
10, 11
N.C.
—
—
EP
EP
No Connection. Not internally connected.
Exposed Pad. Connect EP to GND.
_______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
VS
VCC
MAX5924/MAX5925/MAX5926
BACKPLANE
REMOVABLE CARD
1V TO VCC
2.25V TO 13.2V
RSC
RCB
20kΩ
10Ω
CB
GATE SENSE
V+
OUT
VCC
ON (ON*)
SC_DET
1µF
GND
MAX5925
MAX5926
EN (EN1**)
EN2**
EN
EN2
TC**
CL
PGOOD**
PGOOD (PGOOD*)
GND
SLEW
LATCH** GND
CSLEW
*MAX5925A AND MAX5925C.
**MAX5926.
DC-DC CONVERTER
Figure 1. Typical Operating Circuit (Without RSENSE)
BACKPLANE
REMOVABLE CARD
RSENSE
1V TO VCC
VS
2.25V TO 13.2V
VCC
20kΩ
RCB
10Ω
10Ω
CB
SENSE
GATE
VCC
GND
V+
OUT
ON (ON*)
SC_DET
1µF
EN (EN1**)
EN2**
EN
EN2
VCC
TC**
MAX5924
MAX5926
CL
PGOOD**
PGOOD (PGOOD*)
LATCH**
*MAX5924A AND MAX5924C.
**MAX5926.
GND
GND
SLEW
CSLEW
DC-DC CONVERTER
Figure 2. Typical Operating Circuit (With RSENSE)
_______________________________________________________________________________________
9
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
GATE
50kΩ
VCC
CHARGE PUMP
VZ = 9V
SLEW
N
A
MAX5924
MAX5925
MAX5926
2µA
VCC
RLP
N
VCB,TH
CB
SC_DET
SLOW
COMPARATOR
VS
75kΩ
OUT
TIMER
RCBF
0.2V
VCBF,TH
75kΩ
FAST
COMPARATOR
OSCILLATOR
ICB
TC***
PGOOD*
LOGIC
CONTROL
SENSE
PGOOD**
LATCH***
VCC
EN/(EN1***)
VCC
0.8V
VCC
GND
1.24V
EN2***
*MAX5924B, MAX5924D, MAX5925B, MAX5925D, MAX5926 ONLY.
**MAX5924A, MAX5924C, MAX5925A, MAX5925C, MAX5926 ONLY.
***MAX5926 ONLY.
Figure 3. Functional Diagram
10
______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
The MAX5924/MAX5925/MAX5926 are hot-swap controller ICs designed for applications where a line card is
inserted into a live backplane. Normally, when a line card
is plugged into a live backplane, the card’s discharged
filter capacitors provide a low impedance that can
momentarily cause the main power supply to collapse.
The MAX5924/MAX5925/MAX5926 are designed to
reside either in the backplane or in the removable card
to provide inrush current limiting and short-circuit protection. This is achieved using an external n-channel
MOSFET and an optional external current-sense resistor.
Several critical parameters can be configured:
• Slew rate (inrush current)
MAX5924/MAX5925/MAX5926
Detailed Description
VCC RISES ABOVE VUVLO
NO
ENABLE TRUE?
YES
FAULT MANAGEMENT
UVLO 200ms DELAY
YES
• Circuit-breaker threshold
RSENSE
PRESENT?
NO
ICB,SU = 2 x ICB
DISABLE SLOW
COMPARATOR
• Turn-on voltage
• Fault-management mode (MAX5926)
• Circuit-breaker temperature coefficient (MAX5926)
See the Selector Guide for a device-specific list of factory-preset features and parameters.
DISABLE FAULT PROTECTION,
ENABLE LOAD PROBE
LOAD PROBE
SUCCESSFUL?
NO
YES
SLEW-RATE-LIMITED
STARTUP
Startup Mode
It is important that both VCC and VS rise at a minimum
rate of 100mV/ms during the critical time when power
voltages are below those values required for proper
logic control of internal circuitry. This applies for 0.5V ≤
VCC ≤ 2.5V and 0.5V ≤ VS ≤ 0.8V. This is particularly
true when LATCH is tied high.
The MAX5924/MAX5925/MAX5926 control an external
MOSFET placed in the positive power-supply pathway.
When power is first applied, the MAX5924/MAX5925/
MAX5926 hold the MOSFET off indefinitely if the supply
voltage is below the undervoltage lockout level or if the
device is disabled (see the EN (MAX5924/MAX5925),
EN1/EN2 (MAX5926) section). If neither of these conditions exist, the device enters a UVLO startup delay
period for ≈200ms. Next, the MAX5924/MAX5925/
MAX5926 detect whether an external sense resistor is
present; and then autoconfigure accordingly (see
Figure 4).
• If no sense resistor is present, bilevel fault protection
is disabled and load-probing circuitry is enabled
(see the Load Probing section).
If load probing is not successful, the fault is managed according to the selected fault management
mode (see the Latched and Auto-Retry Fault
Management section).
If load probing (see the Load Probing section) is successful, slew-rate limiting is employed to gradually
turn on the MOSFET.
NO
VGS ≥ VCB,EN
VGS ≥ VTHPGOOD
YES
ENABLE STANDARD BILEVEL
FAULT PROTECTION
BEGIN NORMAL OPERATION
PGOOD
Figure 4. Startup Flow Chart
• If the device detects an external RSENSE, circuitbreaker threshold is set at 2xICB, the slow comparator is disabled, the startup phase begins without
delay for load probing, and slew-rate limiting is
employed to gradually turn on the MOSFET.
During the startup phase, the voltage at the load, VOUT,
rises at a rate determined by the selected slew rate (see
the Slew Rate section). The inrush current, IINRUSH, to
the load is limited to a level proportional to the load
capacitance, CL, and the slew rate:
IINRUSH =
CL × SR
1000
where SR is the slew rate in V/ms and CL is load capacitance in µF.
For operation with and without RSENSE, once VGATE V OUT exceeds V CB,EN , PGOOD and/or PGOOD
assert. When VGATE - VOUT = VCB,EN, the MAX5924/
MAX5925/MAX5926 enable standard bilevel fault protection with normal ICB (see the Bilevel Fault Protection
section).
______________________________________________________________________________________
11
Load Probing
Normal Operation
The MAX5924/MAX5925/MAX5926 load-probing circuitry detects short-circuit conditions during startup. Load
probing is active only when no external R SENSE is
detected. As the device begins load probing, SC_DET
is connected to VCC through an internal switch with an
on-resistance of RLP (Figure 6). VCC then charges the
load with a probe current limited at ≈200mA.
(Figure 1)
IPROBE = (VCC - VOUT)/(RLP + RSC)
If the load voltage does not reach VLP,TH (0.2V typ)
within tLP, a short-circuit fault is detected and the startup mode is terminated according to the selected faultmanagement mode (see the Fault Management section
and Figure 5). If no fault condition is present,
PGOOD/PGOOD asserts at the end of the startup period (see the Turn-On Waveforms in the Typical
Operating Characteristics).
Load probing can only be, and must be, employed
when not using an external RSENSE.
In normal operation, after startup is complete, protection is provided by turning off the external MOSFET
when a fault condition is encountered. Dual-speed/
bilevel fault protection incorporates two comparators
with different thresholds and response times to monitor
the current:
1) Slow comparator. This comparator has a 1.6ms
(typ) response time. The slow comparator ignores
low-amplitude momentary current glitches. After an
extended overcurrent condition, a fault is acknowledged and the MOSFET gate is discharged.
2) Fast comparator. This comparator has a quick
response time and a higher threshold voltage. The
fast comparator turns off the MOSFET immediately
when it detects a large high-current event such as a
short circuit.
VOUT
SR = dV
dt
SR = dV
dt
CL = SMALL
VLP,TH
(0.2V typ)
VOUT
In each case, when a fault is encountered, the powergood output deasserts and the device drives GATE low.
After a fault, the MAX5924A, MAX5924B, MAX5925A,
and MAX5925B latch GATE low and the MAX5924C,
MAX5924D, MAX5925C, and MAX5925D enter the
autoretry mode. The MAX5926 has selectable latched or
autoretry modes. Figure 7 shows the slow comparator
response to an overcurrent fault.
PGOOD*
CL = LARGE
IINRUSH
CL = SMALL
PGOOD**
I PROBE
ILOAD
ILOAD
VGATE
tPROBE < tLP
VTHPGOOD
Figure 5. Startup Waveform
3.0V TO 6.7V
14
VOUT
12
RLP (Ω)
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
10
8
ILIM
ILOAD
6
tCBS
VCC = VS
4
2
4
6
8
10
12
14
VCC (V)
Figure 6. Load-Probe Resistance vs. Supply Voltage
12
*MAX5924B, MAX5924D, MAX5925B, MAX5925D, AND MAX5926 ONLY.
**MAX5924A, MAX5924C, MAX5925A, MAX5925C, AND MAX5926 ONLY.
Figure 7. Slow Comparator Response to an Overcurrent Fault
______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Slow Comparator
The slow comparator is disabled during startup while
the external MOSFET turns on.
If the slow comparator detects an overload condition while
in normal operation (after startup is complete), it turns off
the external MOSFET by discharging the gate capacitance with I GATE,PD . The magnitude of I GATE,PD
depends on the external MOSFET gate-to-source voltage, VGS. The discharge current is strongest immediately following a fault and decreases as the MOSFET
gate is discharged (Figure 8a).
LATCH
FAULT MANAGEMENT
Low
Autoretry mode
High
Latched mode
Fast Comparator
The fast comparator is used for serious current overloads
or short circuits. If the load current reaches the fast comparator threshold, the device quickly forces the MOSFET
off. The fast comparator has a response time of 280ns,
and discharges GATE with IGATE,PD (Figure 8a). The fast
comparator is disabled during startup when no RSENSE
is detected
Latched and Autoretry Fault Management
The MAX5924A, MAX5924B, MAX5925A, and MAX5925B
latch the external MOSFET off when an overcurrent fault
is detected. Following an overcurrent fault, the
MAX5924C, MAX5924D, MAX5925C, and MAX5925D
enter autoretry mode. The MAX5926 can be configured
for either latched or autoretry mode (see Table 1).
In autoretry, a fault turns the external MOSFET off then
automatically restarts the device after the autoretry
delay, tRETRY. During the autoretry delay, pull EN or
EN1 low to restart the device. In latched mode, pull EN
or EN1 low for at least 100µs to clear a latched fault
and restart the device.
Power-Good Outputs
The power-good output(s) are open-drain output(s) that
deassert:
• When VCC < VUVLO
60
VCC = 13.2V
• During tD,UVLO
• When VGS < VTHPGOOD
• During load probing
• When disabled (EN = GND (MAX5924/MAX5925),
EN1 = GND or EN2 = high (MAX5926))
• During fault management
50
IGATE, PD (mA)
Table 1. Selecting Fault Management
Mode (MAX5926)
40
30
20
• During t RETRY or when latched off (MAX5924A,
MAX5924B, MAX5925A, MAX5925B, or MAX5926
(LATCH = low)).
10
0
0
1
2
3
4
5
6
7
VGS (V)
PGOOD/PGOOD asserts only if the part is in normal
mode and no faults are present.
Figure 8a. Gate Discharge Current vs. MOSFET Gate-to-Source
Voltage
______________________________________________________________________________________
13
MAX5924/MAX5925/MAX5926
Bilevel Fault Protection
Bilevel Fault Protection in Startup Mode
Bilevel fault protection is disabled in startup mode, and
is enabled when VGATE-VOUT exceeds VCB,EN at the
end of the startup period.
When no RSENSE is detected, neither slow nor fast comparator is active during startup because the high
RD(ON) of the MOSFET when not fully enhanced would
signal an artificially-high VIN-VSENSE voltage. Load probing prior to startup insures that the output is not short circuited.
When RSENSE is detected, the slow comparator is disabled during startup while the fast comparator remains
active. The overcurrent trip level is higher than normal
during the startup period because the ICB is temporarily
doubled to ICB,SU at this time. This allows higher than
normal startup current to allow for output capacitor
charging current.
Undervoltage Lockout (UVLO)
UVLO circuitry prevents the MAX5924/MAX5925/
MAX5926 from turning on the external MOSFET until VCC
exceeds the UVLO threshold, VUVLO, for tD,UVLO. UVLO
protects the external MOSFET from insufficient gate-drive
voltage, and tD,UVLO ensures that the board is fully
plugged into the backplane and VCC is stable prior to
powering the hot-swapped system. Any input voltage
transient at VCC below the UVLO threshold for more than
the UVLO deglitch period, tDG, resets the device and initiates a startup sequence. Device operation is protected
from momentary input-voltage steps extending below the
UVLO threshold for a deglitch period, tDG. However, the
power-good output(s) may momentarily deassert if the
magnitude of a negative step in VCC exceeds approximately 0.5V, and VCC drops below VUVLO. Operation is
unaffected and the power-good output(s) assert(s) within
200µs as shown in Figure 8b. This figure also shows that
if the UVLO condition exceeds tDG = 900µs (typ), the
power-good output(s) again deassert(s) and the load is
disconnected.
Determining Inrush Current
Determining a circuit’s inrush current is necessary to
choose a proper MOSFET. The MAX5924/MAX5925/
MAX5926 regulate the inrush current by controlling the
output-voltage slew rate, but inrush current is also a
function of load capacitance. Determine an anticipated
inrush current using the following equation:
dVOUT
= CL × SR
dt × 1000
IINRUSH(A) = CL
where CL is the load capacitance in µF and SR is the
selected MAX5924/MAX5925/MAX5926 output slew rate
in V/ms. For example, assuming a load capacitance of
100µF and using the value of SR = 10V/ms, the anticipated inrush current is 1A. If a 16V/ms output slew rate is
used, the inrush current increases to 1.6A. Choose SR
so the maximum anticipated inrush current does not trip
the fast circuit-breaker comparator during startup.
Slew Rate
The MAX5924/MAX5925/MAX5926 limit the slew rate of
VOUT. Connect an external capacitor, CSLEW, between
SLEW and GND to adjust the slew-rate limit. Floating
SLEW sets the maximum slew rate to the minimum value.
Calculate CSLEW using the following equation:
CSLEW = 330 10-9 / SR
where, SR is the desired slew rate in V/ms and CSLEW
is in nF.
This equation is valid for CSLEW ≥ 100nF. For higher
SR, see the Typical Operating Characteristics.
A 2µA (typ) pullup current clamped to 1.4V causes an
initial jump in the gate voltage, VGATE, if CGATE is small
and the slew rate is slow (Figure 3). Figure 9 illustrates
how the addition of gate capacitance minimizes this initial jump. CGATE should not exceed 25nF.
VS = VCC = 13.2V
CSLEW = 1µF
CL = 10µF
GATE
2V/div
VCC
1V/div
VGATE
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
MOSFET ONLY
5V/div
MOSFET AND
CGATE = 20nF
0V
PGOOD
200µs/div
Figure 8b. PGOOD Behavior with Large Negative Input-Voltage
Step when VS is Near VS(MIN)
14
0V
1V/div
10ms/div
Figure 9. Impact of CGATE on the VGATE Waveform
______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
The enable comparators control the on/off function of
the MAX5924/MAX5925/MAX5926. Enable is also used
to reset the fault latch in latch mode. Pull EN or EN1 low
for 100µs to reset the latch. A resistive divider between
EN or EN1, VS, and GND sets the programmable turnon voltage to a voltage greater than VUVLO (Figure 10).
Selecting a Circuit-Breaker Threshold
The MAX5924/MAX5925/MAX5926 offer a circuit-breaker function to protect the external MOSFET and the load
VS
RCB
R1
VCC
CB
GATE
SENSE
OUT
EN (EN1)
R2
MAX5924_
MAX5925_
MAX5926
RSC
SC_DET
(EN2)
GND
( ) ARE FOR MAX5926 ONLY.
VS,TURN-ON =
(R2 + R1) VEN/UVLO
R2
from the potentially damaging effects of excessive current. As load current flows through RDS(ON) (Figure 12)
or RSENSE (Figure 13), a voltage drop is generated.
After VGS exceeds VCB,EN, the MAX5924/MAX5925/
MAX5926 monitor this voltage to detect overcurrent
conditions. If this voltage exceeds the circuit-breaker
threshold, the external MOSFET turns off and the
power-good output(s) deassert(s). To accommodate
different MOSFETs, sense resistors, and load currents,
the MAX5924/MAX5925/MAX5926 voltage across RCB
can be set between 10mV and 500mV. The value of the
circuit-breaker voltage must be carefully selected
based on VS (Figure 11).
No RSENSE Mode
When operating without RSENSE, calculate the circuitbreaker threshold using the MOSFET’s RDS(ON) at the
worst possible operating condition, and add a 20% overcurrent margin to the maximum circuit current. For example, if a MOSFET has an R DS(ON) of 0.06Ω at T A =
+25°C, and a normalized on-resistance factor of 1.75 at
TA = +105°C, the RDS(ON) used for calculation is the
product of these two numbers, or (0.06Ω) x (1.75) =
0.105Ω. Then, if the maximum current is expected to be
2A, using a 20% margin, the current for calculation is
(2A) x (1.2) = 2.4A. The resulting minimum circuit-breaker threshold is then a product of these two numbers, or
(0.105Ω) x (2.4A) = 0.252V. Using this method to choose
a circuit-breaker threshold allows the circuit to operate
under worst-case conditions without causing a circuitbreaker fault, but the circuit-breaker function will still
detect a short circuit or a gross overcurrent condition.
Figure 10. Adjustable Turn-On Voltage
15,000
15,000
TC = 0ppm/°C
12,000
12,000
9000
6000
VS = 1.4V
VS = 1.3V
9000
VS = 1.3V
6000
VS = 1.2V
3000
VS = 1.5V
VS = 1.4V
RCB(MAX) (Ω)
RCB(MAX) (Ω)
VS = 1.5V
TC = 3300ppm/°C
VS = 1.1V
3000
VS = 1.2V
VS = 1.1V
VS = 1.0V
VS = 1.0V
0
0
-40
-15
10
35
60
85
TEMPERATURE (°C)
-40
-15
10
35
60
85
TEMPERATURE (°C)
Figure 11. Maximum Circuit-Breaker Programming Resistor vs. Temperature
______________________________________________________________________________________
15
MAX5924/MAX5925/MAX5926
EN (MAX5924/MAX5925),
EN1/EN2 (MAX5926)
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
To determine the proper circuit-breaker resistor value
use the following equation, which refers to Figure 12:
RCB =
(ITRIPSLOW
x RDS(ON)( T)) + VCB ,OS
ICB
where ITRIPSLOW is the desired slow-comparator trip
current.
The fast-comparator trip current is determined by the
selected RCB value and cannot be adjusted independently. The fast-comparator trip current is given by:
ITRIPFAST =
ICB x (RCBF + RCB) ± VCB ,OS
RDS(ON)( T)
SC_DET must be connected to OUT through the selected RSC when not using RSENSE.
RSENSE Mode
When operating with R SENSE , calculate the circuitbreaker threshold using the worst possible operating
conditions, and add a 20% overcurrent margin to the
maximum circuit current. For example, with a maximum
expected current of 2A, using a 20% margin, the current for calculation is (2A) x (1.2) = 2.4A. The resulting
minimum circuit-breaker threshold is then a product of
this current and RSENSE = 0.06Ω, or (0.06Ω) x (2.4A) =
0.144V. Using this method to choose a false circuitbreaker threshold allows the circuit to operate under
worst-case conditions without causing a circuit-breaker
fault, but the circuit-breaker function will still detect a
short-circuit or a gross overcurrent condition.
To determine the proper circuit-breaker resistor value,
use the following equation, which refers to Figure 13:
(ITRIPSLOW
RCB =
x RSENSE) + VCB ,OS
ICB
where, ITRIPSLOW is the desired slow-comparator trip
current.
The fast-comparator trip current is determined by the
selected RCB value and cannot be adjusted independently. The fast-comparator trip current is given by:
ITRIPFAST =
ICB x (RCBF + RCB) ± VCB ,OS
RSENSE
SC_DET should be connected to V CC when using
RSENSE.
ILOAD
ILOAD
RDS(ON)
RSENSE
VS
VS
VOUT
VOUT
RCB
RCB
SENSE
CB
CB
GATE
SENSE OUT
VCB,TH
MAX5925
MAX5926
RCBF
GATE
VCB,TH
SLOW
COMPARATOR
MAX5925
MAX5926
VCB,OS
RCBF
ICB
VCB,OS
VCBF,TH
Figure 12. Circuit Breaker Using RDS(ON)
16
SLOW
COMPARATOR
VCB,OS
FAST
COMPARATOR
FAST
COMPARATOR
TC
SELECT
OUT
TC
SELECT
ICB
VCB,OS
VCBF,TH
Figure 13. Circuit Breaker Using RSENSE
______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Applications Information
Component Selection
n-Channel MOSFET
Most circuit component values may be calculated with
the aid of the MAX5924–MAX5926. The "Design calculator for choosing component values" software can be
downloaded from the MAX5924–MAX5926 Quickview on
the Maxim website.
Select the external n-channel MOSFET according to the
application’s current and voltage level. Table 3 lists some
recommended components. Choose the MOSFET’s
on-resistance, RDS(ON), low enough to have a minimum
voltage drop at full load to limit the MOSFET power dissipation. High RDS(ON) can cause undesired power
loss and output ripple if the board has pulsing loads or
triggers an external undervoltage reset monitor at full
load. Determine the device power-rating requirement to
accommodate a short circuit on the board at startup
with the device configured in autoretry mode.
Using the MAX5924/MAX5925/MAX5926 in latched mode
allows the consideration of MOSFETs with higher RDS(ON)
and lower power ratings. A MOSFET can typically with-
TC
TCICB (ppm/°C)
High
0
Low
3300
Table 3. Suggested External MOSFETs
APPLICATION
CURRENT (A)
PART
DESCRIPTION
1
International Rectifier
IRF7401
SO-8
2
Siliconix Si4378DY
SO-8
5
Siliconix SUD40N02-06
DPAK
10
Siliconix SUB85N02-03
D2PAK
50
45
VCB AND VSENSE (mV)
ITRIPSLOW x RDS(ON)(T) ≥ ICB(T) x RCB + |VCB,OS|
where VCB,OS is the worst-case offset voltage. Figure 14
graphically portrays operating conditions for a MOSFET
with a 4500ppm/°C temperature coefficient.
Table 2. Programming the Temperature
Coefficient (MAX5926)
VS = VCC = 13.2V, RCB = 672Ω, ITRIPSLOW = 5A,
RDS(ON)(25) = 6.5mΩ
CIRCUIT-BREAKER TRIP REGION
(VSENSE ≥ VCB)
40
35
30
VSENSE = RDS(ON)(T) x ILOAD(MAX)
(4500ppm/°C)
25
VCB = ICB(T) x RCB + VCB,OS
(3300ppm/°C)
20
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
Figure 14. Circuit-Breaker Trip Point and Current-Sense
Voltage vs. Temperature
stand single-shot pulses with higher dissipation than the
specified package rating. Low MOSFET gate capacitance is not necessary since the inrush current limiting is
achieved by limiting the gate dv/dt. Table 4 lists some
recommended manufacturers and components.
Be sure to select a MOSFET with an appropriate gate
drive (see the Typical Operating Characteristics ).
Typically, for V CC less than 3V, select a 2.5V V GS
MOSFET.
______________________________________________________________________________________
17
MAX5924/MAX5925/MAX5926
Circuit-Breaker Temperature Coefficient
In applications where the external MOSFET’s on-resistance is used as a sense resistor to determine overcurrent conditions, a 3300ppm/°C temperature coefficient
is desirable to compensate for the RDS(ON) temperature coefficient. Use the MAX5926’s TC input to select
the circuit-breaker programming current’s temperature
coefficient, TCICB (see Table 2). The MAX5924 temperature coefficient is preset to 0ppm/°C, and the
MAX5925’s is preset to 3300ppm/°C.
Setting TCICB to 3300ppm/°C allows the circuit-breaker
threshold to track and compensate for the increase in the
MOSFET’s RDS(ON) with increasing temperature. Most
MOSFETs have a temperature coefficient within a
3000ppm/°C to 7000ppm/°C range. Refer to the MOSFET
data sheet for a device-specific temperature coefficent.
RDS(ON) and ICB are temperature dependent, and can
therefore be expressed as functions of temperature. At
a given temperature, the MAX5925/MAX5926 indicate
an overcurrent condition when:
MAX5924/MAX5925/MAX5926
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Table 4. Component Manufacturers
COMPONENT
Sense Resistors
MOSFETs
MANUFACTURER
PHONE
Dale-Vishay
402-564-3131
IRC
828-264-8861
www.irctt.com
Fairchild
888-522-5372
www.fairchildsemi.com
International Rectifier
310-233-3331
www.irf.com
Optional Sense Resistor
Select the sense resistor in conjunction with RCB to set
the slow and fast circuit-breaker thresholds (see the
Selecting a Circuit-Breaker Threshold section). The
sense-resistor power dissipation depends on the device
configuration. If latched mode is selected, PRSENSE =
(IOVERLOAD)2 x RSENSE; if autoretry is selected, then
P RSENSE = (I OVERLOAD ) 2 x R SENSE x (t ON /t RETRY ).
Choose a sense-resistor power rating of twice the
PRSENSE for long-term reliable operation. In addition,
ensure that the sense resistor has an adequate I2T rating
to survive instantaneous short-circuit conditions.
No-Load Operation
The internal circuitry is capable of sourcing a current at
the OUT terminal of up to 120µA from a voltage VIN +
VGS. If there is no load on the circuit, the output capacitor
will charge to a voltage above VIN until the external MOSFET’s body diode conducts to clamp the capacitor voltage at VIN plus the body-diode VF. When testing or
operating with no load, it is therefore recommended that
the output capacitor be paralleled with a resistor of value:
R = VX / 120µA
where VX is the maximum acceptable output voltage
prior to hot-swap completion.
Design Procedure
Given:
• VCC = VS = 5V
• CL = 150µF
• Full-Load Current = 5A
• No RSENSE
• IINRUSH = 500mA
Procedures:
1) Calculate the required slew rate and corresponding
CSLEW:
I
V
SR = INRUSH = 3.3
1000 × CL
ms
18
WEBSITE
www.vishay.com
CSLEW =
330 × 10 −9
330 × 10 −9
=
= 0.1µF
SR
3.3 V
ms
2) Select a MOSFET and determine the worst-case
power dissipation.
3) Minimize power dissipation at full load current and
at high temperature by selecting a MOSFET with an
appropriate RDS(ON). Assume a 20°C temperature
difference between the MAX5924/MAX5925/
MAX5926 and the MOSFET.
For example, at room temperature the IRF7822’s
RDS(ON) = 6.5mΩ. The temperature coefficient for
this device is 4000ppm/°C. The maximum RDS(ON)
for the MOSFET at TJ(MOSFET) = +105°C is:
ppm ⎞
⎛
RDS(ON)105 = 6.5mΩ × ⎜1 + (105°C − 25°C) × 4000
⎟
⎝
°C ⎠
= 8.58mΩ
The power dissipation in the MOSFET at full load is:
PD = I2 R = (5A)2 × 8.58mΩ = 215mW
4) Select RCB.
Since the MOSFET’s temperature coefficient is
4000ppm/°C, which is greater than TC ICB
(3300ppm/°C), calculate the circuit-breaker threshold at high temperature so the circuit breaker is
guaranteed not to trip at lower temperature during
normal operation (Figure 15).
ITRIPSLOW = IFULL LOAD + 20% = 5A + 20% = 6A
RDS(ON)105 = 8.58mΩ (max), from step 2
ICB85 = 58µA x (1 + (3300ppm/°C x (85 - 25)°C)
= 69.5µA (min)
RCB =
(ITRIPSLOW
x RDS(ON)105
ICB85
) + VCB,OS
RCB = ((6A x 8.58mΩ) + 4.7mV)/69.5µA = 808Ω
______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
the two devices are equal, the circuit-breaker trip
threshold is most accurate. Keep the MOSFET and the
MAX5925/MAX5926 as close to each other as possible
to facilitate thermal coupling.
HIGH-CURRENT PATH
SENSE RESISTOR
RCB
MAX5924
MAX5925
MAX5926
Figure 15. Kelvin Connection for the Current-Sense Resistor
Selector Guide
POWER-GOOD OUTPUT
CIRCUIT-BREAKER
TEMPCO
(ppm/°C)
FAULT MANAGEMENT
MAX5924A
0
MAX5924B
0
MAX5924C
PGOOD
(OPEN-DRAIN)
PGOOD
(OPEN-DRAIN)
Latched
✓
—
Latched
—
✓
0
Autoretry
✓
—
MAX5924D
0
Autoretry
—
✓
MAX5925A
3300
Latched
✓
—
MAX5925B
3300
Latched
—
✓
MAX5925C
3300
Autoretry
✓
—
MAX5925D
3300
Autoretry
—
✓
0 or 3300 (Selectable)
Latched or Autoretry (Selectable)
✓
✓
PART
MAX5926
______________________________________________________________________________________
19
MAX5924/MAX5925/MAX5926
Layout Considerations
Keep all traces as short as possible and maximize the
high-current trace dimensions to reduce the effect of
undesirable parasitic inductance. Place the MAX5924/
MAX5925/MAX5926 close to the card’s connector. Use
a ground plane to minimize impedance and inductance. Minimize the current-sense resistor trace length
(<10mm), and ensure accurate current sensing with
Kelvin connections.
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 package 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.
It is important to maximize the thermal coupling between
the MOSFET and the MAX5925/MAX5926 to balance the
device junction temperatures. When the temperatures of
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
MAX5924/MAX5925/MAX5926
Pin Configurations
TOP VIEW
VCC 1
16 CB
SC_DET 2
VCC 1
SC_DET
2
EN
3
PGOOD (PGOOD)
GND
10 CB
9
SENSE
8
OUT
4
7
GATE
5
6
SLEW
MAX5924
MAX5925
GND 5
9
Chip Information
TRANSISTOR COUNT: 3751
PROCESS: BiCMOS
N
VOUT
Package Information
SENSE GATE
OUT
VCC
MAX5924
MAX5926
For the latest package outline information and land patterns,
go to www.maxim-ic.com/packages. Note that a "+", "#", or "-"
in the package code indicates RoHS status only. Package
drawings may show a different suffix character, but the drawing pertains to the package regardless of RoHS status.
PACKAGE TYPE
PACKAGE CODE
DOCUMENT NO.
10 µMAX
U10CN+1
21-0061
16 QSOP-EP
E16E-1
21-0112
SEE FIGURE 2 FOR A DETAILED TYPICAL OPERATING CIRCUIT WITH RSENSE.
20
TC
QSOP
2.25V TO 13.2V
GND
10 N.C.
LATCH 8
RCB
GND
11 N.C.
EP
TYPICAL OPERATION WITH RSENSE
REMOVABLE CARD
RSENSE
1V TO VCC
CB
12 SLEW
EN2 6
Typical Operating Circuits
(continued)
VCC
13 GATE
MAX5926
PGOOD 7
( ) FOR THE MAX5924A, MAX5924C, MAX5925A, AND MAX5925C.
VS
14 OUT
EN1 3
PGOOD 4
µMAX
BACKPLANE
15 SENSE
______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
REVISION
NUMBER
REVISION
DATE
0
8/05
Initial release
1
6/06
Revised data sheet title, General Description, Features, EC table, Typical
Operating Circuit, and added No-Load Operation section.
1–13, 15–18
2
10/06
Initial release of MAX5924BEUB and revised EC table.
1–4, 10–12
3
4/10
Revised EC table.
DESCRIPTION
PAGES
CHANGED
—
2–4
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 ____________________ 21
© 2010 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
MAX5924/MAX5925/MAX5926
Revision History