MAX5925A [MAXIM]
1V to 13.2V, n-Channel Hot-Swap Controllers Require No Sense Resistor; 1V至13.2V ， n沟道热插拔控制器，无需检测电阻
| 型号： | MAX5925A |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 1V to 13.2V, n-Channel Hot-Swap Controllers Require No Sense Resistor |
| 文件： | 总22页 (文件大小：382K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3443; Rev 2; 10/06
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
General Description
Features
♦ Hot Swap 1V to 13.2V with V
♦ Drive High-Side n-Channel MOSFET
♦ Operation With or Without R
≥ 2.25V
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 sup-
plies ranging from 1V to 13.2V provided that the device
CC
SENSE
♦ Temperature-Compensated RDS(ON) Sensing
♦ Protected During Turn-On into Shorted Load
♦ Adjustable Circuit-Breaker Threshold
♦ Programmable Slew-Rate Control
supply voltage, V , is at or above 2.25V and the hot-
CC
S
swapped supply, V , does not exceed V
.
CC
The MAX5924/MAX5925/MAX5926 hot-swap controllers
limit the inrush current to the load and provide a circuit-
breaker function for overcurrent protection. The devices
operate with or without a sense resistor. When operat-
ing 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.
♦ Programmable Turn-On Voltage
♦ Autoretry or Latched Fault Management
♦ 10-Pin µMAX or 16-Pin QSOP Packages
®
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
10 µMAX
MAX5924AEUB
MAX5924BEUB
MAX5924CEUB*
MAX5924DEUB*
MAX5925AEUB
MAX5925BEUB*
MAX5925CEUB*
MAX5925DEUB*
MAX5926EEE
The MAX5924/MAX5925/MAX5926 include many inte-
grated 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.
10 µMAX
10 µMAX
10 µMAX
10 µMAX
10 µMAX
The MAX5924/MAX5925/MAX5926 are available with
open-drain PGOOD and/or PGOOD outputs. The
MAX5925/MAX5926 also feature a circuit breaker with
10 µMAX
10 µMAX
16 QSOP–EP**
temperature-compensated R
sensing. The
DS(ON)
*Future product—contact factory for availability.
**EP = Exposed pad.
MAX5926 features a selectable 0ppm/°C or 3300ppm/°C
temperature coefficient. The MAX5924 temperature coef-
ficient is 0ppm/°C and the MAX5925 temperature coeffi-
cient is 3300ppm/°C. Autoretry and latched fault-
management configurations are available (see the
Selector Guide).
Typical Operating Circuits
TYPICAL OPERATION WITHOUT R
SENSE
BACKPLANE
REMOVABLE CARD
N
Applications
V
1V TO V
CC
OUT
Base Stations
V
S
2.25V TO 13.2V
V
RAID
CC
R
CB
R
SC
Remote-Access Servers
Network Routers and Switches
Servers
OUT
CB
GATE SENSE
SC_DET
V
CC
Portable Device Bays
MAX5925
MAX5926
GND
GND
µMAX is a registered trademark of Maxim Integrated Products, Inc.
SEE FIGURE 1 FOR A DETAILED TYPICAL OPERATING CIRCUIT WITHOUT R
.
SENSE
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/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted).
Continuous Power Dissipation (T = +70°C)
A
V
.........................................................................-0.3V to +14V
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
CC
GATE*.....................................................................-0.3V to +20V
All Other Pins ............-0.3V to the lower of (V + 0.3V) or +14V
SC_DET Current (200ms pulse width, 15% duty cycle) ...140mA
CC
Continuous Current (all other pins).....................................20mA
*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
CC
(V , EN (MAX5924/MAX5925), EN1 (MAX5926) = +2.25V to +13.2V; EN2 (MAX5926) = 0V; V (see Figure 1) = +1.05V to V ; T =
A
S
CC
-40°C to +85°C, unless otherwise noted. Typical values are at V
= +25°C, unless otherwise noted.) (Note 1)
= 5V, R = 500Ω from OUT to GND, C = 1µF, SLEW = open, T
CC
A
L
L
PARAMETER
POWER SUPPLIES
Operating Range
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
V
2.25
1.05
13.2
V
V
CC
CC
V Operating Range
S
V
V as defined in Figure 1
V
CC
S
S
Supply Current
I
FET is fully enhanced, SC_DET = V
1.5
2.5
2.47
350
mA
CC
CC
UNDERVOLTAGE LOCKOUT (UVLO)
UVLO Threshold
V
Default value, V and V increasing, Figure 1
1.73
123
2.06
900
200
V
UVLO
S
CC
V
V
UVLO Deglitch Time
UVLO Startup Delay
t
(Note 2)
µs
ms
CC
CC
DG
D,UVLO
t
LOAD-PROBE
2.25V < V
< 5V
4
3
30
10
65
20
CC
Load-Probe Resistance (Note 3)
R
Ω
LP
5V < V
< 13.2V
CC
Load-Probe Timeout
t
43
172
102
200
205
235
ms
mV
LP
Load-Probe Threshold Voltage
CIRCUIT BREAKER
V
(Note 4)
LP,TH
I
TC = high (MAX5926), MAX5924
= 2.25V,
34
44
37
51
42
58
CB
V
CC
T
= +25°C
A
TC = low (MAX5926),
MAX5925 (Note 5)
I
I
CB25
5V ≤ V
≤ 13.2V,
CC
49
47
58
54
52
63
58
60
70
Circuit-Breaker Programming
Current
T
= +25°C
A
µA
V
= 2.25V,
CC
T
= +85°C
A
TC = low (MAX5926),
MAX5925 (Note 5)
CB85
5V ≤ V
≤ 13.2V,
CC
T
= +85°C
A
2
_______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
ELECTRICAL CHARACTERISTICS (continued)
CC
(V , EN (MAX5924/MAX5925), EN1 (MAX5926) = +2.25V to +13.2V; EN2 (MAX5926) = 0V; V (see Figure 1) = +1.05V to V ; T =
A
S
CC
-40°C to +85°C, unless otherwise noted. Typical values are at V
= +25°C, unless otherwise noted.) (Note 1)
= 5V, R = 500Ω from OUT to GND, C = 1µF, SLEW = open, T
CC
A
L
L
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
µA
Circuit-Breaker Programming
Current During Startup
I
2 x I
CB
CB,SU
Circuit-Breaker Enable Threshold
V
V
- V , rising gate voltage (Note 6)
OUT
2.3
3.6
0.3
4.65
4.7
V
CB,EN
CB_OS
GATE
Circuit-Breaker Comparator
Offset Voltage
V
mV
Fast Circuit-Breaker Offset
Resistor
R
CBF
Figure 3
1.2
1.9
2.7
kΩ
Slow Circuit-Breaker Delay
Fast Circuit-Breaker Delay
t
V
V
- V
- V
= 10mV
0.95
1.6
2.95
ms
ns
CBS
CB
CB
SENSE
t
= 500mV
280
CBF
SENSE
Circuit-Breaker Trip Gate
Pulldown Current
I
V
= 2.5V, V
= 13.2V
13.5
27
mA
GATE,PD
GATE
CC
MAX5924, TC = high (MAX5926)
MAX5925, TC = low (MAX5926)
0
Circuit-Breaker Temperature
Coefficient
TC
ppm/°C
µA
ICB
3300
OUT Current
I
120
OUT
MOSFET DRIVER
External Gate Drive
V
V
- V
2.25V ≤ V ≤ 13.2V
CC
3.0
4.91
9.5
6.70
V
GS
GATE
OUT
SLEW = open, C
= 10nF
2.19
GATE
Load Voltage Slew Rate
SR
V/ms
µA
C
= 300nF, C
= 10nF (Note 8)
GATE
0.84
SLEW
GATE
Gate Pullup Current Capacity
I
V
= 0V
239
GATE
ENABLE COMPARATOR
V
V
(MAX5924/MAX5925) or
EN
EN, EN1 Reference Threshold
EN, EN1 Hysteresis
V
0.747
0.795
30
0.850
50
V
EN/UVLO
(MAX5926) rising
EN1
V
mV
nA
EN,HYS
EN (MAX5924/MAX5925) = V
EN1 (MAX5926) = V
,
CC
EN, EN1 Input Bias Current
I
8
EN
CC
DIGITAL OUTPUTS (PGOOD, PGOOD)
Power-Good Output Low Voltage
V
I
= 1mA
0.3
0.2
0.4
1
V
OL
OL
Power-Good Output Open-Drain
Leakage Current
I
PGOOD/PGOOD = 13.2V
- V , rising gate voltage
µA
OH
Power-Good Trip Point
Power-Good Hysteresis
V
V
V
3.6
4.7
V
V
THPGOOD
GATE
OUT
CB_EN
V
0.36
PG,HYS
_______________________________________________________________________________________
3
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
ELECTRICAL CHARACTERISTICS (continued)
CC
(V , EN (MAX5924/MAX5925), EN1 (MAX5926) = +2.25V to +13.2V; EN2 (MAX5926) = 0V; V (see Figure 1) = +1.05V to V ; T =
S
CC
A
-40°C to +85°C, unless otherwise noted. Typical values are at V
= +25°C, unless otherwise noted.) (Note 1)
= 5V, R = 500Ω from OUT to GND, C = 1µF, SLEW = open, T
A
L L
CC
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
3.3
UNITS
LOGIC AND TIMING (TC, LATCH (MAX5926), EN2 (MAX5926)
Autoretry Delay
Input Voltage
t
Autoretry mode
0.6
2.0
1.6
s
V
RETRY
V
IH
V
0.4
IL
Input Bias Current
I
Logic high at 13.2V
3
µA
BIAS
MAX5924A/ MAX5924B
MAX5925A/ MAX5925B
MAX5926 in latched mode
Time to Clear a Latched Fault
T
200
µS
CLR
Note 1: All devices are 100% tested at T = +25°C and +85°C. All temperature limits at -40°C are guaranteed by design.
A
Note 2: V
drops 30% below the undervoltage lockout voltage during t
are ignored.
CC
DG
Note 3: R is the resistance measured between V
and SC_DET during the load-probing phase, t .
LP
CC
LP
Note 4: Tested at +25°C & +85°C. Guaranteed by design at -40°C.
Note 5: The circuit-breaker programming current increases linearly from V
Supply Voltage graph in the Typical Operating Characteristics.
Note 6: See the Startup Mode section for more information.
= 2.25V to 5V. See the Circuit-Breaker Current vs.
CC
Note 7: V
is clamped to 17V (typ) above ground.
GATE
-9
Note 8: dv/dt = 330 x 10 /C
(V/ms), nMOS device used for measurement was IRF9530N. Slew rate is measured at the load.
SLEW
Typical Operating Characteristics
(V
= 5V, C = 1µF, C
= 330nF, C
= 10nF, R = 500Ω, Figure 1, T = +25°C, unless otherwise noted.)
CC
L
SLEW
GATE
L
A
MAX5926 SUPPLY CURRENT
vs. TEMPERATURE
GATE-DRIVE VOLTAGE
vs. SUPPLY VOLTAGE
MAX5926 SUPPLY CURRENT
vs. SUPPLY VOLTAGE
2.4
2.0
1.6
1.2
0.8
0.4
0
7
6
5
4
3
2
2.0
V
= V
V
= V
CC S
CC
S
ENABLED
DISABLED
1.6
1.2
0.8
0.4
0
V
= 13.2V
CC
V
= 1V
S
V
= 5.0V
CC
V
= V
CC
S
V
= 3V
S
V
= 3.0V
V
= 5V
CC
S
V
= 2.25V
CC
-40
-15
10
35
60
85
2
4
6
8
10
12
14
2
4
6
8
10
12
14
TEMPERATURE (°C)
V (V)
CC
V
(V)
CC
4
_______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Typical Operating Characteristics (continued)
(V
= 5V, C = 1µF, C
= 330nF, C
= 10nF, R = 500Ω, Figure 1, T = +25°C, unless otherwise noted.)
CC
L
SLEW
GATE
L
A
CIRCUIT-BREAKER CURRENT
vs. SUPPLY VOLTAGE (TC = 3300ppm/°C)
GATE DRIVE VOLTAGE
vs. TEMPERATURE
CIRCUIT-BREAKER CURRENT
vs. HOT-SWAP VOLTAGE
55
53
51
49
47
6.0
56
52
48
44
40
36
V
= V
S
CC
V
= V
S
CC
TC = 3300ppm/°C
5.5
5.0
4.5
4.0
3.5
3.0
V
= 5.0V
CC
V
= 3.0V
CC
V
= 13.2V
CC
TC = 0ppm/°C
V
= 13.2V
CC
2
4
6
8
10
12
14
-40
-15
10
35
60
85
0
2
4
6
8
10
12
14
V
(V)
TEMPERATURE (°C)
V
(V)
CC
S
CIRCUIT-BREAKER CURRENT
vs. SUPPLY VOLTAGE (TC = 0ppm/°C)
CIRCUIT-BREAKER PROGRAMMING
CURRENT vs. TEMPERATURE
SLEW RATE vs. C
SLEW
39.4
39.2
39.0
38.8
38.6
38.4
38.2
80
70
60
50
40
30
20
100
10
1
V
= V
S
V
= V = 5V
S
CC
CC
TC = 3300ppm/°C
TC = 0ppm/°C
0.1
2
4
6
8
10
12
14
-40
-15
10
35
60
85
0
500
1000
C (nF)
SLEW
2000
1500
V
(V)
TEMPERATURE (°C)
CC
_______________________________________________________________________________________
5
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Typical Operating Characteristics (continued)
(V
= 5V, C = 1µF, C
L
= 330nF, C
= 10nF, R = 500Ω, Figure 1, T = +25°C, unless otherwise noted.)
CC
SLEW
GATE
L
A
TURN-ON WAVEFORM
(C = OPEN)
TURN-ON WAVEFORM
(C = 330nF)
SLEW
SLEW
MAX5924 toc10
MAX5924 toc11
GATE
5V/div
0V
GATE
5V/div
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 toc13
MAX5924 toc12
1A/div
0A
EN1
5V/div
0V
I
FET
t
CBS
10V/div
GATE
5V/div
0V
GATE
OUT
0V
10V/div
0V
PGOOD
5V/div
0V
5V/div
0V
PGOOD
2µs/div
400µs/div
SHORT-CIRCUIT CIRCUIT-BREAKER EVENT
AUTORETRY DELAY
MAX5924 toc14
MAX5924 toc15
I
FET
1A/div
EN1
5V/div
0V
t
D,UVLO
0A
t
RETRY
GATE
OUT
5V/div
5V/div
0V
SC_DET
OUT
0V
5V/div
0V
100mV/div
0V
5V/div
0V
PGOOD
2µs/div
400ms/div
6
_______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Typical Operating Characteristics (continued)
(V
= 5V, C = 1µF, C
= 330nF, C
= 10nF, R = 500Ω, Figure 1, T = +25°C, unless otherwise noted.)
CC
L
SLEW
GATE L A
OVERCURRENT FAULT AND
AUTORETRY DELAY
UVLO DELAY AND LOAD PROBING
MAX5924 toc16
MAX5924 toc17
EN1
EN1
5V/div
0V
5V/div
0V
GATE
5V/div
0V
t
t
LP
D,UVLO
5V/div
0V
5V/div
0V
SC_DET
OUT
SC_DET
OUT
200mV/div
0V
100mV/div
0V
400ms/div
40ms/div
UVLO RESPONSE
UVLO DEGLITCH RESPONSE
MAX5924 toc19
MAX5924 toc18
>t
DG
2V/div
GATE
GATE
2V/div
0V
<t
DG
0V
1V/div
1V/div
0V
V
CC
V
CC
0V
200µs/div
200µs/div
_______________________________________________________________________________________
7
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Pin Description
PIN
MAX5924A/ MAX5924B/
MAX5924C/ MAX5924D/
MAX5925A/ MAX5925B/
MAX5925C MAX5925D
NAME
FUNCTION
MAX5926
Power-Supply Input. Connect V
to a voltage between 2.47V and 13.2V.
CC
1
1
1
V
CC
V
CC
must always be equal to or greater than V (see Figure 1).
S
Short-Circuit Detection Output. Connect SC_DET to V
through a series
OUT
resistor, R , when not using R
. SC_DET forces current (limited to
SENSE
SC
≈200mA) into the external load through R at startup to determine whether
SC
2
2
2
SC_DET
EN
there is a short circuit (load probing). Connect SC_DET directly to V when
CC
using R , Do not connect SC_DET to V
SENSE
when not using R
in an
SENSE
CC
attempt to disable load probing.
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
3
3
—
V
, EN, and GND sets the programmable turn-on voltage.
CC
4
—
5
—
4
4
7
5
PGOOD Open-Drain Active-Low Power-Good Output
PGOOD Open-Drain Active-High Power-Good Output
5
GND
Ground
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.
6
6
12
SLEW
Gate-Drive Output. Connect GATE to the gate of the external n-channel
MOSFET.
7
8
7
8
13
14
GATE
OUT
Output Voltage. Connect OUT to the source of the external MOSFET.
Circuit-Breaker Sense Input. Connect SENSE to OUT when not using an
external R
MOSFET when using an external R
(Figure 1). Connect SENSE to the drain of the external
9
9
15
16
SENSE
CB
SENSE
(Figure 2).
SENSE
Circuit-Breaker Threshold Programming Input. Connect an external resistor,
, from CB to V to set the circuit-breaker threshold voltage.
10
10
R
CB
S
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 V , EN1, and GND sets the
CC
—
—
3
EN1
programmable turn-on voltage while EN2 is low.
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.
—
—
—
—
—
—
6
8
9
EN2
LATCH
TC
Latch Mode Input. Drive LATCH low for autoretry mode. Drive LATCH high for
latched mode.
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
EP
N.C.
EP
No Connection. Not internally connected.
Exposed Pad. Connect EP to GND.
8
_______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
BACKPLANE
REMOVABLE CARD
1V TO V
CC
V
S
2.25V TO 13.2V
V
CC
R
SC
20kΩ
R
CB
10Ω
CB
GATE SENSE OUT
SC_DET
V+
ON (ON*)
V
CC
1µF
GND
C
L
MAX5925
MAX5926
PGOOD**
EN (EN1**)
EN2**
EN
PGOOD (PGOOD*)
EN2
GND
SLEW
GND
TC** LATCH**
C
SLEW
*MAX5925A AND MAX5925C.
**MAX5926.
DC-DC CONVERTER
Figure 1. Typical Operating Circuit (Without R
)
SENSE
BACKPLANE
REMOVABLE CARD
1V TO V
R
SENSE
CC
V
S
2.25V TO 13.2V
V
CC
20kΩ
R
CB
10Ω
10Ω
CB
SENSE GATE
OUT
V+
ON (ON*)
V
CC
SC_DET
1µF
GND
C
L
MAX5924
MAX5926
PGOOD**
EN (EN1**)
EN2**
EN
PGOOD (PGOOD*)
EN2
GND
SLEW
GND
TC**
LATCH**
C
SLEW
V
CC
*MAX5924A AND MAX5924C.
**MAX5926.
DC-DC CONVERTER
Figure 2. Typical Operating Circuit (With R
)
SENSE
_______________________________________________________________________________________
9
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
GATE
50kΩ
V
CC
CHARGE PUMP
V = 9V
Z
MAX5924
MAX5925
MAX5926
2µA
N
SLEW
A
V
CC
R
LP
N
SC_DET
OUT
V
CB,TH
CB
SLOW
COMPARATOR
V
S
75kΩ
75kΩ
TIMER
R
CBF
0.2V
V
OSCILLATOR
CBF,TH
FAST
COMPARATOR
I
TC***
CB
PGOOD*
PGOOD**
LOGIC
CONTROL
SENSE
LATCH***
V
V
CC
EN/(EN1***)
V
CC
0.8V
CC
GND
1.24V
*MAX5924B, MAX5924D, MAX5925B, MAX5925D, MAX5926 ONLY.
**MAX5924A, MAX5924C, MAX5925A, MAX5925C, MAX5926 ONLY.
***MAX5926 ONLY.
EN2***
Figure 3. Functional Diagram
10 ______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Detailed Description
V
RISES ABOVE V
CC
UVLO
The MAX5924/MAX5925/MAX5926 are hot-swap con-
troller 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 pro-
tection. This is achieved using an external n-channel
MOSFET and an optional external current-sense resistor.
NO
ENABLE TRUE?
YES
FAULT MANAGEMENT
UVLO 200ms DELAY
NO
DISABLE FAULT PROTECTION,
ENABLE LOAD PROBE
R
YES
SENSE
Several critical parameters can be configured:
• Slew rate (inrush current)
PRESENT?
• Circuit-breaker threshold
• Turn-on voltage
I
= 2 x I
CB
CB,SU
NO
LOAD PROBE
SUCCESSFUL?
DISABLE SLOW
COMPARATOR
• Fault-management mode (MAX5926)
• Circuit-breaker temperature coefficient (MAX5926)
See the Selector Guide for a device-specific list of fac-
tory-preset features and parameters.
YES
SLEW-RATE-LIMITED
STARTUP
Startup Mode
ENABLE STANDARD BILEVEL
FAULT PROTECTION
BEGIN NORMAL OPERATION
It is important that both V
and V rise at a minimum
S
YES
CC
V
GS
≥ V
CB,EN
GS
≥ V
NO
V
THPGOOD
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 ≤
PGOOD
V
≤ 2.5V and 0.5V ≤ V ≤ 0.8V. This is particularly
S
CC
Figure 4. Startup Flow Chart
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 condi-
tions 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 the device detects an external R
, circuit-
SENSE
breaker threshold is set at 2xI , the slow compara-
CB
tor 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, V
rises at a rate determined by the selected slew rate (see
the Slew Rate section). The inrush current, I , to
,
OUT
INRUSH
the load is limited to a level proportional to the load
capacitance, C , and the slew rate:
L
C × SR
1000
L
I
=
INRUSH
• If no sense resistor is present, bilevel fault protection
is disabled and load-probing circuitry is enabled
(see the Load Probing section).
where SR is the slew rate in V/ms and C is load capac-
L
itance in µF.
If load probing is not successful, the fault is man-
aged according to the selected fault management
mode (see the Latched and Auto-Retry Fault
Management section).
For operation with and without R
, once V
-
GATE
SENSE
V
exceeds V
, PGOOD and/or PGOOD
CB,EN
OUT
assert. When V
MAX5925/MAX5926 enable standard bilevel fault pro-
- V
= V
, the MAX5924/
CB,EN
GATE
OUT
If load probing (see the Load Probing section) is suc-
cessful, slew-rate limiting is employed to gradually
turn on the MOSFET.
tection with normal I
section).
(see the Bilevel Fault Protection
CB
______________________________________________________________________________________ 11
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Load Probing
The MAX5924/MAX5925/MAX5926 load-probing circuit-
ry detects short-circuit conditions during startup. Load
Normal Operation
In normal operation, after startup is complete, protec-
tion 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:
probing is active only when no external R
is
SENSE
detected. As the device begins load probing, SC_DET
is connected to V through an internal switch with an
CC
on-resistance of R (Figure 6). V
then charges the
CC
LP
load with a probe current limited at ≈200mA.
= (V - V )/(R + R (Figure 1)
(0.2V typ)
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 acknowl-
edged and the MOSFET gate is discharged.
I
)
SC
PROBE
CC
OUT
LP
If the load voltage does not reach V
within t , a short-circuit fault is detected and the start-
LP,TH
LP
up mode is terminated according to the selected fault-
management mode (see the Fault Management section
and Figure 5). If no fault condition is present,
PGOOD/PGOOD asserts at the end of the startup peri-
od (see the Turn-On Waveforms in the Typical
Operating Characteristics).
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.
Load probing can only be, and must be, employed
In each case, when a fault is encountered, the power-
good 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.
when not using an external R
.
SENSE
V
OUT
SR = dV
dt
SR = dV
dt
C
L
= SMALL
V
LP,TH
(0.2V typ)
PGOOD*
V
OUT
C
L
= LARGE
I
INRUSH
C
L
= SMALL
PGOOD**
I
PROBE
I
LOAD
I
LOAD
t
< t
V
GATE
PROBE LP
V
THPGOOD
Figure 5. Startup Waveform
3.0V TO 6.7V
14
12
10
8
V
OUT
I
LIM
I
LOAD
tCBS
6
V
= V
S
CC
4
*MAX5924B, MAX5924D, MAX5925B, MAX5925D, AND MAX5926 ONLY.
**MAX5924A, MAX5924C, MAX5925A, MAX5925C, AND MAX5926 ONLY.
2
4
6
8
10
12
14
V
(V)
CC
Figure 7. Slow Comparator Response to an Overcurrent Fault
Figure 6. Load-Probe Resistance vs. Supply Voltage
12 ______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Bilevel Fault Protection
Bilevel Fault Protection in Startup Mode
Table 1. Selecting Fault Management
Mode (MAX5926)
Bilevel fault protection is disabled in startup mode, and
LATCH
Low
FAULT MANAGEMENT
Autoretry mode
Latched mode
is enabled when V
exceeds V
at the
CB,EN
GATE-VOUT
end of the startup period.
High
When no R is detected, neither slow nor fast com-
SENSE
parator is active during startup because the high
RD(ON) of the MOSFET when not fully enhanced would
Fast Comparator
signal an artificially-high V -V
voltage. Load prob-
IN SENSE
The fast comparator is used for serious current overloads
or short circuits. If the load current reaches the fast com-
parator threshold, the device quickly forces the MOSFET
off. The fast comparator has a response time of 280ns,
ing prior to startup insures that the output is not short cir-
cuited.
When R
is detected, the slow comparator is dis-
SENSE
and discharges GATE with I
(Figure 8a). The fast
abled 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.
GATE,PD
comparator is disabled during startup when no R
is detected
SENSE
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).
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 capaci-
In autoretry, a fault turns the external MOSFET off then
automatically restarts the device after the autoretry
delay, t
. During the autoretry delay, pull EN or
tance with I
. The magnitude of I
GATE,PD
RETRY
GATE,PD
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.
depends on the external MOSFET gate-to-source volt-
age, V . The discharge current is strongest immedi-
GS
ately following a fault and decreases as the MOSFET
gate is discharged (Figure 8a).
Power-Good Outputs
The power-good output(s) are open-drain output(s) that
deassert:
60
• When V
< V
CC
UVLO
V
CC
= 13.2V
50
40
30
20
10
0
• During t
• When V < V
• During load probing
• When disabled (EN = GND (MAX5924/MAX5925),
EN1 = GND or EN2 = high (MAX5926))
D,UVLO
GS
THPGOOD
• During fault management
• During t
or when latched off (MAX5924A,
RETRY
MAX5924B, MAX5925A, MAX5925B, or MAX5926
(LATCH = low)).
3
4
0
1
2
5
6
7
PGOOD/PGOOD asserts only if the part is in normal
mode and no faults are present.
V
(V)
GS
Figure 8a. Gate Discharge Current vs. MOSFET Gate-to-Source
Voltage
______________________________________________________________________________________ 13
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Undervoltage Lockout (UVLO)
dV
dt × 1000
OUT
I
(A) = C
= C × SR
L
UVLO circuitry prevents the MAX5924/MAX5925/
INRUSH
L
MAX5926 from turning on the external MOSFET until V
CC
. UVLO
exceeds the UVLO threshold, V
, for t
UVLO
D,UVLO
where C is the load capacitance in µF and SR is the
L
protects the external MOSFET from insufficient gate-drive
voltage, and t ensures that the board is fully
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 anticipat-
ed 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.
D,UVLO
plugged into the backplane and V
is stable prior to
CC
powering the hot-swapped system. Any input voltage
transient at V
below the UVLO threshold for more than
CC
the UVLO deglitch period, t , resets the device and ini-
DG
tiates a startup sequence. Device operation is protected
from momentary input-voltage steps extending below the
UVLO threshold for a deglitch period, t
However, the
DG.
Slew Rate
power-good output(s) may momentarily deassert if the
magnitude of a negative step in V exceeds approxi-
The MAX5924/MAX5925/MAX5926 limit the slew rate of
CC
V
OUT
. Connect an external capacitor, C
, between
SLEW
mately 0.5V, and V
drops below V
. Operation is
CC
UVLO
SLEW and GND to adjust the slew-rate limit. Floating
SLEW sets the maximum slew rate to the minimum value.
unaffected and the power-good output(s) assert(s) within
200µs as shown in Figure 8b. This figure also shows that
Calculate C
using the following equation:
SLEW
if the UVLO condition exceeds t
= 900µs (typ), the
DG
C
SLEW
= 330 ✕ 10-9 / SR
power-good output(s) again deassert(s) and the load is
disconnected.
where, SR is the desired slew rate in V/ms and C
is in nF.
SLEW
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:
This equation is valid for C
≥ 100nF. For higher
SLEW
SR, see the Typical Operating Characteristics.
A 2µA (typ) pullup current clamped to 1.4V causes an
initial jump in the gate voltage, V
, if C
is small
GATE
GATE
and the slew rate is slow (Figure 3). Figure 9 illustrates
how the addition of gate capacitance minimizes this ini-
tial jump. C
should not exceed 25nF.
GATE
V = V = 13.2V
S
CC
C
= 1µF
SLEW
C = 10µF
L
GATE
2V/div
MOSFET ONLY
V
CC
5V/div
1V/div
MOSFET AND
= 20nF
C
GATE
0V
0V
1V/div
PGOOD
200µs/div
10ms/div
on the V
Figure 8b. PGOOD Behavior with Large Negative Input-Voltage
Step when V is Near V
Figure 9. Impact of C
Waveform
GATE
GATE
S
S(MIN)
14 ______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
rent. As load current flows through R
(Figure 12)
EN (MAX5924/MAX5925),
EN1/EN2 (MAX5926)
DS(ON)
or R
(Figure 13), a voltage drop is generated.
SENSE
After V
exceeds V
, the MAX5924/MAX5925/
CB,EN
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
GS
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,
EN or EN1, V , and GND sets the programmable turn-
S
on voltage to a voltage greater than V
(Figure 10).
UVLO
the MAX5924/MAX5925/MAX5926 voltage across R
CB
Selecting a Circuit-Breaker Threshold
The MAX5924/MAX5925/MAX5926 offer a circuit-break-
er function to protect the external MOSFET and the load
from the potentially damaging effects of excessive cur-
can be set between 10mV and 500mV. The value of the
circuit-breaker voltage must be carefully selected
based on V (Figure 11).
S
No R
Mode
SENSE
When operating without R
, calculate the circuit-
SENSE
breaker threshold using the MOSFET’s R
at the
DS(ON)
V
S
worst possible operating condition, and add a 20% over-
current margin to the maximum circuit current. For exam-
R
CB
ple, if a MOSFET has an R
of 0.06Ω at T
=
A
DS(ON)
R
1
+25°C, and a normalized on-resistance factor of 1.75 at
= +105°C, the R used for calculation is the
V
GATE
CB
EN (EN1)
CC
T
A
DS(ON)
SENSE
OUT
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-break-
er 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 circuit-
breaker fault, but the circuit-breaker function will still
detect a short circuit or a gross overcurrent condition.
R
2
MAX5924_
MAX5925_
MAX5926
R
SC
SC_DET
(EN2)
GND
(R + R ) V
EN/UVLO
2
1
( ) ARE FOR MAX5926 ONLY.
V
=
S,TURN-ON
R
2
Figure 10. Adjustable Turn-On Voltage
15,000
15,000
TC = 0ppm/°C
TC = 3300ppm/°C
V
V
V
= 1.5V
= 1.4V
= 1.3V
S
S
S
12,000
12,000
9000
6000
3000
0
V
= 1.5V
S
9000
6000
3000
0
V
V
V
V
V
= 1.4V
= 1.3V
= 1.2V
= 1.1V
= 1.0V
S
S
S
S
S
V
V
V
= 1.2V
= 1.1V
= 1.0V
S
S
S
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
Figure 11. Maximum Circuit-Breaker Programming Resistor vs. Temperature
______________________________________________________________________________________ 15
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:
minimum circuit-breaker threshold is then a product of
this current and R = 0.06Ω, or (0.06Ω) x (2.4A) =
0.144V. Using this method to choose a false circuit-
breaker 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.
SENSE
I
x R
(T) + V
(
)
TRIPSLOW
DS(ON)
CB,OS
R
=
CB
I
CB
where I
current.
is the desired slow-comparator trip
TRIPSLOW
To determine the proper circuit-breaker resistor value,
use the following equation, which refers to Figure 13:
The fast-comparator trip current is determined by the
selected R value and cannot be adjusted indepen-
CB
I
x R
+ V
(
)
TRIPSLOW
SENSE
OS
CB,
dently. The fast-comparator trip current is given by:
R
=
CB
I
CB
I
x R
(
+ R
V
CB,OS
)
CB
CB
CBF
I
=
TRIPFAST
where, I
current.
is the desired slow-comparator trip
TRIPSLOW
R
(T)
DS(ON)
SC_DET must be connected to OUT through the select-
The fast-comparator trip current is determined by the
selected R value and cannot be adjusted indepen-
ed R when not using R
SC
.
SENSE
CB
dently. The fast-comparator trip current is given by:
R
Mode
SENSE
, calculate the circuit-
When operating with R
SENSE
I
x R
(
+ R
V
CB,OS
)
CB
CB
CBF
breaker 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 cur-
rent for calculation is (2A) x (1.2) = 2.4A. The resulting
I
=
TRIPFAST
R
SENSE
SC_DET should be connected to V
SENSE
when using
CC
R
.
I
LOAD
I
LOAD
R
DS(ON)
R
SENSE
V
S
V
OUT
V
V
S
OUT
R
CB
R
CB
SENSE
GATE
OUT
CB
CB GATE
SENSE OUT
SLOW
COMPARATOR
V
CB,TH
SLOW
COMPARATOR
V
CB,TH
MAX5925
MAX5926
R
V
CBF
CB,OS
MAX5925
MAX5926
V
CB,OS
R
CBF
FAST
COMPARATOR
FAST
COMPARATOR
I
CB
I
CB
TC
TC
SELECT
V
CB,OS
V
SELECT
CB,OS
V
CBF,TH
V
CBF,TH
Figure 12. Circuit Breaker Using R
Figure 13. Circuit Breaker Using R
DS(ON)
SENSE
16 ______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Circuit-Breaker Temperature Coefficient
Table 2. Programming the Temperature
Coefficient (MAX5926)
In applications where the external MOSFET’s on-resis-
tance is used as a sense resistor to determine overcur-
rent conditions, a 3300ppm/°C temperature coefficient
TC
TC
(ppm/°C)
ICB
is desirable to compensate for the R
tempera-
DS(ON)
High
Low
0
ture coefficient. Use the MAX5926’s TC input to select
the circuit-breaker programming current’s temperature
3300
coefficient, TC
(see Table 2). The MAX5924 temper-
ICB
ature coefficient is preset to 0ppm/°C, and the
MAX5925’s is preset to 3300ppm/°C.
Table 3. Suggested External MOSFETs
APPLICATION
CURRENT (A)
Setting TC
to 3300ppm/°C allows the circuit-breaker
ICB
PART
DESCRIPTION
threshold to track and compensate for the increase in the
MOSFET’s R with increasing temperature. Most
DS(ON)
International Rectifier
IRF7401
1
SO-8
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.
2
5
Siliconix Si4378DY
SO-8
Siliconix SUD40N02-06
Siliconix SUB85N02-03
DPAK
D2PAK
R
and I
are temperature dependent, and can
CB
DS(ON)
10
therefore be expressed as functions of temperature. At
a given temperature, the MAX5925/MAX5926 indicate
an overcurrent condition when:
50
45
40
35
30
25
20
I
x R
(T) ≥ I (T) x R + |V
|
V = V = 13.2V, R = 672Ω, I = 5A,
TRIPSLOW
DS(ON)
TRIPSLOW
DS(ON)
CB
CB
CB,OS
S
CC
CB
R
(25) = 6.5mΩ
where V
is the worst-case offset voltage. Figure 14
CB,OS
CIRCUIT-BREAKER TRIP REGION
graphically portrays operating conditions for a MOSFET
with a 4500ppm/°C temperature coefficient.
(V
SENSE
≥ V
CB
)
Applications Information
Component Selection
V
= R
(T) x I
CB,OS
SENSE
DS(ON)
LOAD(MAX)
n-Channel MOSFET
Most circuit component values may be calculated with
the aid of the MAX5924–MAX5926. The "Design calcula-
tor for choosing component values" software can be
downloaded from the MAX5924–MAX5926 Quickview on
the Maxim website.
(4500ppm/°C)
V
= I (T) x R + V
CB CB
CB
(3300ppm/°C)
-40
-15
10
35
60
85
110
TEMPERATURE (°C)
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
Figure 14. Circuit-Breaker Trip Point and Current-Sense
Voltage vs. Temperature
on-resistance, R
, low enough to have a minimum
DS(ON)
voltage drop at full load to limit the MOSFET power dis-
sipation. High R 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.
stand single-shot pulses with higher dissipation than the
specified package rating. Low MOSFET gate capaci-
tance is not necessary since the inrush current limiting is
achieved by limiting the gate dv/dt. Table 4 lists some
recommended manufacturers and components.
DS(ON)
Be sure to select a MOSFET with an appropriate gate
drive (see the Typical Operating Characteristics).
Using the MAX5924/MAX5925/MAX5926 in latched mode
Typically, for V
MOSFET.
less than 3V, select a 2.5V V
GS
CC
allows the consideration of MOSFETs with higher R
DS(ON)
and lower power ratings. A MOSFET can typically with-
______________________________________________________________________________________ 17
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Table 4. Component Manufacturers
COMPONENT
MANUFACTURER
Dale-Vishay
IRC
PHONE
WEBSITE
402-564-3131
828-264-8861
888-522-5372
310-233-3331
www.vishay.com
www.irctt.com
Sense Resistors
Fairchild
www.fairchildsemi.com
www.irf.com
MOSFETs
International Rectifier
Optional Sense Resistor
−9
−9
330 × 10
330 × 10
Select the sense resistor in conjunction with R
to set
CB
C
=
=
= 0.1µF
SLEW
V
SR
the slow and fast circuit-breaker thresholds (see the
Selecting a Circuit-Breaker Threshold section). The
sense-resistor power dissipation depends on the device
3.3
ms
2) Select a MOSFET and determine the worst-case
power dissipation.
configuration. If latched mode is selected, P
=
RSENSE
(I
P
)2 x R
OVERLOAD
; if autoretry is selected, then
OVERLOAD
SENSE
3) Minimize power dissipation at full load current and
at high temperature by selecting a MOSFET with an
= (I
)2 x R
x (t /t
).
RSENSE
SENSE
ON RETRY
Choose a sense-resistor power rating of twice the
appropriate R
. Assume a 20°C temperature
DS(ON)
P
for long-term reliable operation. In addition,
RSENSE
difference between the MAX5924/MAX5925/
MAX5926 and the MOSFET.
ensure that the sense resistor has an adequate I2T rating
to survive instantaneous short-circuit conditions.
For example, at room temperature the IRF7822’s
No-Load Operation
The internal circuitry is capable of sourcing a current at
R
= 6.5mΩ. The temperature coefficient for
DS(ON)
this device is 4000ppm/°C. The maximum R
DS(ON)
the OUT terminal of up to 120µA from a voltage V
+
for the MOSFET at T
= +105°C is:
IN
J(MOSFET)
V
GS
. If there is no load on the circuit, the output capacitor
ppm
°C
⎛
⎞
will charge to a voltage above V until the external MOS-
IN
R
= 6.5mΩ × 1+ (105°C − 25°C) × 4000
⎜
⎟
⎠
DS(ON)105
FET’s body diode conducts to clamp the capacitor volt-
⎝
age at VIN plus the body-diode V . When testing or
F
= 8.58mΩ
operating with no load, it is therefore recommended that
the output capacitor be paralleled with a resistor of value:
The power dissipation in the MOSFET at full load is:
2
2
P
= I R = (5A) × 8.58mΩ = 215mW
R = V / 120µA
X
D
where V is the maximum acceptable output voltage
X
prior to hot-swap completion.
4) Select R
.
CB
Since the MOSFET’s temperature coefficient is
4000ppm/°C, which is greater than TC
(3300ppm/°C), calculate the circuit-breaker thresh-
old at high temperature so the circuit breaker is
guaranteed not to trip at lower temperature during
normal operation (Figure 15).
Design Procedure
ICB
Given:
• V
= V = 5V
S
CC
• C = 150µF
L
• Full-Load Current = 5A
• No R
I
= I
+ 20% = 5A + 20% = 6A
TRIPSLOW
FULL LOAD
SENSE
R
= 8.58mΩ (max), from step 2
DS(ON)105
• I
= 500mA
INRUSH
I
= 58µA x (1 + (3300ppm/°C x (85 - 25)°C)
= 69.5µA (min)
CB85
Procedures:
1) Calculate the required slew rate and corresponding
C
SLEW
:
I
x R
+ V
CB,OS
(
TRIPSLOW
)
DS(ON)105
R
CB
=
I
V
ms
INRUSH
I
CB85
SR =
= 3.3
1000 × C
L
R
= ((6A x 8.58mΩ) + 4.7mV)/69.5µA = 808Ω
CB
18 ______________________________________________________________________________________
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.
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 induc-
tance. Minimize the current-sense resistor trace length
(<10mm), and ensure accurate current sensing with
Kelvin connections.
HIGH-CURRENT PATH
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.
SENSE RESISTOR
R
CB
MAX5924
MAX5925
MAX5926
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
Figure 15. Kelvin Connection for the Current-Sense Resistor
Selector Guide
POWER-GOOD OUTPUT
CIRCUIT-BREAKER
PART
TEMPCO
(ppm/°C)
FAULT MANAGEMENT
PGOOD
(OPEN-DRAIN)
PGOOD
(OPEN-DRAIN)
MAX5924A
0
Latched
Latched
✓
—
✓
—
✓
MAX5924B
MAX5924C
MAX5924D
MAX5925A
MAX5925B
MAX5925C
MAX5925D
MAX5926
0
0
Autoretry
—
✓
0
Autoretry
—
✓
3300
Latched
—
✓
3300
3300
Latched
—
✓
Autoretry
—
✓
3300
Autoretry
—
✓
0 or 3300 (Selectable)
Latched or Autoretry (Selectable)
✓
______________________________________________________________________________________ 19
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Pin Configurations
TOP VIEW
V
CC
1
2
3
4
5
6
7
8
16 CB
SC_DET
EN1
15 SENSE
14 OUT
13 GATE
12 SLEW
11 N.C.
10 N.C.
V
1
2
3
4
5
10 CB
CC
SC_DET
9
8
7
6
SENSE
PGOOD
GND
MAX5924
MAX5925
EN
PGOOD (PGOOD)
GND
OUT
MAX5926
GATE
SLEW
EN2
PGOOD
LATCH
µMAX
9
TC
( ) FOR THE MAX5924A, MAX5924C, MAX5925A, AND MAX5925C.
QSOP-EP
Typical Operating Circuits
(continued)
Chip Information
TRANSISTOR COUNT: 3751
PROCESS: BiCMOS
TYPICAL OPERATION WITH R
SENSE
BACKPLANE
REMOVABLE CARD
R
SENSE
N
V
OUT
1V TO V
CC
V
S
2.25V TO 13.2V
V
CC
R
CB
CB
OUT
SENSE GATE
V
CC
MAX5924
MAX5926
GND
GND
SEE FIGURE 2 FOR A DETAILED TYPICAL OPERATING CIRCUIT WITH R
.
SENSE
20 ______________________________________________________________________________________
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Package Information
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
e
4X S
10
10
INCHES
MAX
MILLIMETERS
MAX
1.10
0.15
0.95
3.05
3.00
3.05
3.00
5.05
0.70
DIM MIN
MIN
-
A
-
0.043
0.006
0.037
0.120
0.118
0.120
0.118
0.199
A1
A2
D1
D2
E1
E2
H
0.002
0.030
0.116
0.114
0.116
0.114
0.187
0.05
0.75
2.95
2.89
2.95
2.89
4.75
0.40
H
Ø0.50 0.1
0.6 0.1
L
0.0157 0.0275
0.037 REF
L1
b
0.940 REF
0.007
0.0106
0.177
0.270
0.200
1
1
e
0.0197 BSC
0.500 BSC
0.6 0.1
c
0.0035 0.0078
0.0196 REF
0.090
BOTTOM VIEW
0.498 REF
S
α
TOP VIEW
0°
6°
0°
6°
D2
E2
GAGE PLANE
A2
c
A
E1
b
L
α
A1
D1
L1
FRONT VIEW
SIDE VIEW
PROPRIETARY INFORMATION
TITLE:
PACKAGE OUTLINE, 10L uMAX/uSOP
APPROVAL
DOCUMENT CONTROL NO.
REV.
1
21-0061
1
______________________________________________________________________________________ 21
1V to 13.2V, n-Channel Hot-Swap Controllers
Require No Sense Resistor
Package Information (continued)
(The package drawing(s) in this data sheet may not reflect the most current specifications. For the latest package outline information,
go to www.maxim-ic.com/packages.)
PACKAGE OUTLINE,
16L QSOP, .150" EXPOSED PAD
1
21-0112
C
1
Revision History
Pages changed at Rev 1: 1–13, 15–18,
Title change—all pages.
Pages changed at Rev 2: 1–4, 10–12
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.
22 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2006 Maxim Integrated Products
is a registered trademark of Maxim Integrated Products, Inc.
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