Maxim MAX5946 Dual pci express, hot-plug controller Datasheet

19-3483; Rev 0; 11/04
KIT
ATION
EVALU
LE
B
A
IL
A
AV
Dual PCI Express, Hot-Plug
Controller
♦ PCI Express Compliant
♦ Hot Swaps 12V, 3.3V, and 3.3V Auxiliary for 2
PCI-E Slots
♦ Integrated Power MOSFET for Auxiliary Supply
Rails
♦ Controls dI/dt and dV/dt
♦ Active Current Limiting Protects Against
Overcurrent/Short-Circuit Conditions
♦ Programmable Current-Limit Timeout
♦ PWRGD Signal Outputs with Programmable
Power-On Reset (POR) (160ms Default)
♦ Latched FAULT Signal Output after Overcurrent
or Overtemperature Fault
♦ Attention Switch Inputs/Outputs with 4ms
Debounce
♦ Present-Detect Inputs
♦ Forced-On Inputs Facilitates Testing
♦ Thermal Shutdown
♦ Allows Control through SMBus with an I/O
Expander
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX5946AETX
-40°C to +85°C
36 Thin QFN
MAX5946LETX
-40°C to +85°C
36 Thin QFN
36 35 34 33 32 31 30 29 28
Applications
Servers
Desktop Mobile Server Platforms
Workstations
Embedded Devices
12VIN
INPUT1
OUTPUT1
OUTPUT2
INPUT2
TIM
TOP VIEW
PGND
GND
Pin Configuration
PORADJ
The MAX5946 dual hot-plug controller is designed for
PCI Express™ applications. The device provides hotplug control for 12V, 3.3V, and 3.3V auxiliary supplies of
two PCI express slots. The MAX5946’s logic inputs/outputs allow interfacing directly with the system hot-plug
management controller or through an SMBus™ with an
external I/O expander. An integrated debounced attention switch and present-detect signals are included to
simplify system design.
The MAX5946 drives four external n-channel MOSFETs
to control the 12V and 3.3V main outputs. The 3.3V auxiliary outputs are controlled through internal 0.3Ω
n-channel MOSFETs. Internal charge pumps provide
gate drive for the 12V outputs while the gate drive of
the 3.3V output is driven by the 12V input supply. The
3.3V auxiliary outputs are completely independent from
the main outputs with their own charge pumps.
At power-up, the MAX5946 keeps all of the external
MOSFETs off until the supplies rise above their respective undervoltage lockout (UVLO) thresholds. The
device keeps the internal MOSFETs off only until the
auxiliary input supply rises above its UVLO threshold.
Upon a turn-on command, the MAX5946 enhances the
external and internal MOSFETs slowly with a constant
gate current to limit the power-supply inrush current.
The MAX5946 actively limits the current of all outputs at
all times and shuts down if an overcurrent condition
persists for longer than a programmable overcurrent
timeout. Thermal-protection circuitry also shuts down all
outputs if the die temperature exceeds +150°C. After an
overcurrent or overtemperature fault condition, the
MAX5946L latches off while the MAX5946A automatically restarts after a restart time delay. The device is available in a 36-pin (6mm × 6mm) thin QFN package and
operates over the -40°C to +85°C temperature range.
Features
PRES-DETA
FONA
1
27
2
26
ONA
AUXONA
12SA+
12SA-
3
25
4
24
6
22
12GA
3.3SA+
3.3SA-
7
21
8
20
9
19
5
23
MAX5946
PRES-DETB
FONB
ONB
AUXONB
12SB+
12SB12GB
3.3SB+
3.3SB-
SMBus is a trademark of Intel Corp.
PCI Express is a trademark of PCI-SIG Corp.
3.3GB
FAULTB
3.3GA
FAULTA
PWRGDA
3.3VAUXOA
3.3VAUXIN
3.3VAUXOB
PWRGDB
10 11 12 13 14 15 16 17 18
Typical Application Circuit appears at end of data sheet.
THIN QFN
________________________________________________________________ Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
1
MAX5946
General Description
MAX5946
Dual PCI Express, Hot-Plug
Controller
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
12VIN......................................................................-0.3V to +14V
12GA, 12GB ..............................................-0.3V to (V12VIN + 6V)
12SA+, 12SA-, 12SB+, 12SB-,
3.3GA, 3.3GB .....................................-0.3V to (V12VIN + 0.3V)
3.3VAUXIN, ONA, ONB, FAULTA, FAULTB ............-0.3V to +6V
PWRGDA, PWRGDB ................................................-0.3V to +6V
PGND ....................................................................-0.3V to +0.3V
All Other Pins to GND......................-0.3V to (V3.3VAUXIN + 0.3V)
Continuous Power Dissipation (TA = +70°C)
36-Pin Thin QFN (derate 26.3mW/°C above +70°C).....2.105W
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
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
(V12VIN = V12S_- = V12S_+ = 12V, V3.3S_+ = V3.3S_- = V3.3VAUXIN = VON_ = VAUXON_ = VFON__ = 3.3V, PWRGD_ = FAULT_ = PORADJ
= TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
12V SUPPLY
12V Supply Voltage Range
12VIN Undervoltage Lockout
12VIN Supply Current
V12VIN
V12UVLO
I12VIN
V12VIN rising
10.8
12
13.2
9.5
10
10.5
V
Hysteresis
0.1
V12VIN = 13.2V
0.5
1
mA
49
54
59
mV
V12G_ = GND
4
5
6
µA
12VIN CONTROL
12VIN Current-Limit
Threshold (V12S_+ - V12S_-)
V12ILIM
12G_ Gate Charge Current
I12G_CHG
Normal turn-off, ON_ = GND, V12G_ = 2V
50
150
250
µA
12G_ Gate Discharge Current
I12G_DIS
Output short-circuit condition, strong gate pulldown
to regulation, V12VIN - V12S_ ≥ 1V, V12G_= 5V
50
120
180
mA
12G_ Gate High Voltage
(V12G_ - V12VIN)
V12G_H
I12G_ = 1µA
4.8
5.3
5.8
V
12G_ Threshold Voltage For
PWRGD_ Assertion (Note 2)
VPGTH12
Referred to V12VIN, I12G_ = 1µA
-3.0
-4
-4.8
V
1
µA
20
60
µA
3.0
3.3
3.6
V
2.52
2.65
2.78
12S_- Input Bias Current
12S_+ Input Bias Current
3.3V SUPPLY
3.3V Supply Voltage Range
Undervoltage Lockout
(Note 3)
2
V3.3SA+,
V3.3SB+
3.3SA+ rising
Hysteresis
30
_______________________________________________________________________________________
V
mV
Dual PCI Express, Hot-Plug
Controller
(V12VIN = V12S_- = V12S_+ = 12V, V3.3S_+ = V3.3S_- = V3.3VAUXIN = VON_ = VAUXON_ = VFON__ = 3.3V, PWRGD_ = FAULT_ = PORADJ
= TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
17
20
23
mV
3.3V CONTROL
3.3V Current-Limit Threshold
(V3.3S_+ - V3.3S_-)
V3.3ILIM
3.3G_ Gate Charge Current
I3.3G_CHG
V3.3G_ = GND
4
5
6
µA
ON_ = GND, V3.3G_ = 2V
50
150
250
µA
3.3G_ Gate Discharge
Current
I3.3G_DIS
Output short-circuit condition, strong gate pulldown
to regulation, V3.3S_+ - V3.3S_ ≥ 1V, V3.3G_ = 5V
100
150
220
mA
3.3G_ Gate High Voltage
(V3.3G_ - V3.3S_+)
V3.3G_H
Sourcing 1µA
4.5
5.5
6.8
V
Referred to V3.3VAUXIN, I3.3G_ = 1µA
-3.0
-4
-4.5
V
1
µA
20
60
µA
3.0
3.3
3.6
V
2.52
2.65
2.78
V
3.3G_ Threshold Voltage For
PWRGD_ Assertion (Note 2)
VPGTH3.3
3.3S_- Input Bias Current
3.3S_+ Input Bias Current
3.3V AUXILIARY SUPPLY
3.3VAUXIN Supply Voltage
Range
3.3VAUXIN Undervoltage
Lockout
V3.3VAUXIN
V3.3VAUXUVLO
3.3VAUXIN rising
Hysteresis
30
3.3VAUXIN Supply Current
V3.3VAUXIN = 3.6V
1.5
3.3VAUXIN to 3.3VAUXO_
Maximum Dropout
I3.3VAUXO_ = 375mA
3.3VAUXO_ Current-Limit
Threshold
3.3VAUXO_ shorted to GND
3.3VAUXO_ Threshold For
PWRGD_ Assertion
(V3.3VAUXIN - V3.3VAUXO_)
(Note 3)
376
470
VPGTH3.3AUX
mV
3
mA
225
mV
564
mA
400
mV
2.0
V
LOGIC SIGNALS
Input-Logic Threshold
(ON_, FON_, AUXON_,
PRES-DET_, INPUT_)
Rising edge
1.0
25
Hysteresis
Input Bias Current
(ON_, AUXON_, INPUT_)
FON_, PRES-DET_ Internal
Pullup
ON_, AUXON_ High-to-Low
Deglitch Time
25
50
4
mV
1
µA
75
kΩ
µs
_______________________________________________________________________________________
3
MAX5946
ELECTRICAL CHARACTERISTICS (continued)
MAX5946
Dual PCI Express, Hot-Plug
Controller
ELECTRICAL CHARACTERISTICS (continued)
(V12VIN = V12S_- = V12S_+ = 12V, V3.3S_+ = V3.3S_- = V3.3VAUXIN = VON_ = VAUXON_ = VFON__ = 3.3V, PWRGD_ = FAULT_ = PORADJ
= TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, TA = -40°C to +85°C, unless otherwise noted.
Typical values are at TA = +25°C.) (Note 1)
PARAMETER
PRES-DET_ High-to-Low
Deglitch Time
PWRGD_ Power-On Reset
Time (Note 2)
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
3
5
7
ms
PORADJ = open
90
160
250
RPORADJ = 20kΩ
35
55
75
RPORADJ = 100kΩ
145
265
380
tDEG
tPOR_HL
RPORADJ = 200kΩ
PWRGD_ Low-to-High
Deglitch Time
PWRGD_, FAULT_ OutputHigh Leakage Current
FAULT_ Timeout
570
4
tPOR_LH
PWRGD_, FAULT_ Output
Low Voltage
µs
Sinking 2mA
0.1
Sinking 30mA
0.7
VPWRGD_ = VFAULT_ = 5.5V
tFAULT
ms
1
TIM = open
5.5
11
17.0
RTIM = 15kΩ
1.4
2.6
3.8
RTIM = 120kΩ
12
22
32
RTIM = 300kΩ
V
µA
ms
59
FAULT_ Timeout During
Startup
tSU
2 x tFAULT
ms
Autorestart Delay Time
tRESTART
64 x tFAULT
ms
tRESET
100
µs
+150
°C
20
°C
Fault Reset Minimum Pulse
Width (Note 4)
Thermal-Shutdown Threshold
TSD
TJ rising
Thermal-Shutdown Threshold
Hysteresis
OUTPUT_ Debounce Time
tDBC
2.6
OUTPUT_ High Voltage
Sourcing 2mA
OUTPUT_ Low Voltage
Sinking 2mA
Note 1:
Note 2:
Note 3:
Note 4:
4
4.4
6.2
V3.3VAUXIN
V3.3VAUXIN
- 0.3
100% production tested at TA = +25°C. Parameters over temperature are guaranteed by design.
PWRGD_ asserts a time tPOR_HL after VPGTH12, VPGTH3.3, and VPGTH3.3AUX conditions are met.
The UVLO for the 3.3V supply is sensed at 3.3SA+.
This is the time that ON_ or AUXON_ must stay low when resetting a fault condition.
_______________________________________________________________________________________
0.4
ms
V
V
Dual PCI Express, Hot-Plug
Controller
(V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical
Application Circuit.)
1.4
1.2
1.0
0.8
0.6
10
35
60
1.8
1.7
1.6
ON_ OR AUXON_
1.5
1.4
1.3
0.4
1.2
0.2
1.1
85
MAX5946 toc03
1.9
THRESHOLD VOLTAGE (V)
1.6
SUPPLY CURRENT (mA)
-15
1.0
-40
-15
10
35
60
-40
85
-15
10
35
60
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
3.3VAUXO_ OUTPUT VOLTAGE vs. CURRENT
12G_ AND 3.3G_ GATE CHARGE
CURRENT vs. TEMPERATURE
12G_ AND 3.3G_ GATE DISCHARGE
CURRENT vs. TEMPERATURE
2.5
2.0
1.5
1.0
0.5
5.25
12G_
5.20
5.15
5.10
5.05
5.00
3.3G_
4.95
170
85
MAX5946 toc06
5.30
GATE DISCHARGE CURRENT (µA)
3.0
5.35
MAX5946 toc05
MAX5946 toc04
3.5
165
3.3G_
160
155
12G_
150
4.90
0
4.85
0
0.1
0.2
0.3
0.4
0.5
0.6
145
-40
-15
10
35
60
85
-40
-15
10
35
60
TEMPERATURE (°C)
TEMPERATURE (°C)
3.3VAUX INTERNAL SWITCH
MAXIMUM DROPOUT vs. TEMPERATURE
12V AND 3.3V CURRENT-LIMIT THRESHOLD
VOLTAGE vs. TEMPERATURE
AUXILIARY CURRENT LIMIT
vs. TEMPERATURE
0.12
0.10
0.08
0.06
0.04
0.02
12V CURRENT-SENSE
THRESHOLD
40
3.3V CURRENT-SENSE
THRESHOLD
30
20
10
-40
-15
10
35
TEMPERATURE (°C)
60
85
0.495
0.490
0.485
0.480
0.475
0.470
0.465
0.460
0.455
0
0
85
MAX5946 toc09
50
0.500
AUXILIARY CURRENT LIMIT (A)
0.14
MAX5946 toc08
0.16
60
CURRENT-LIMIT THRESHOLD VOLTAGE (mV)
AUXILIARY OUTPUT CURRENT = 375mA
0.18
MAX5946 toc07
OUTPUT CURRENT (A)
0.20
DROPOUT VOLTAGE (V)
2.0
MAX5946 toc02
MAX5946 toc01
1.8
0
-40
OUTPUT VOLTAGE (V)
2.0
GATE CHARGE CURRENT (µA)
SUPPLY CURRENT (mA)
0.505
0.504
0.503
0.502
0.501
0.500
0.499
0.498
0.497
0.496
0.495
0.494
0.493
0.492
0.491
0.490
ON AND AUXON LOW-TO-HIGH THRESHOLD
VOLTAGE vs. TEMPERATURE
3.3VAUXIN SUPPLY CURRENT
vs. TEMPERATURE
12VIN INPUT SUPPLY CURRENT
vs. TEMPERATURE
0.450
-40
-15
10
35
TEMPERATURE (°C)
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
_______________________________________________________________________________________
5
MAX5946
Typical Operating Characteristics
Typical Operating Characteristics (continued)
(V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical
Application Circuit.)
12VIN UNDERVOLTAGE LOCKOUT
THRESHOLD vs. TEMPERATURE
3.3VAUXIN UNDERVOLTAGE LOCKOUT
THRESHOLD vs. TEMPERATURE
10.15
MAX5946 toc11
2.70
MAX5946 toc10
10.20
2.68
10.10
UVLO THRESHOLD (V)
UVLO THRESHOLD (V)
MAX5946
Dual PCI Express, Hot-Plug
Controller
10.05
10.00
9.95
2.66
2.64
9.90
2.62
9.85
9.80
2.60
-40
-15
10
35
60
85
-40
TEMPERATURE (°C)
-15
10
35
60
85
TEMPERATURE (°C)
12V TURN-ON/OFF TIME
3.3V TURN-ON/OFF TIME
MAX5946 toc12
MAX5946 toc13
3.3V OUTPUT
5V/div
12V OUTPUT
10V/div
3.3G_
10V/div
12G_
20V/div
ON_
5V/div
ON_
5V/div
PWRGD_
5V/div
PWRGD_
5V/div
40ms/div
40ms/div
3.3V AUXILIARY TURN-ON/OFF TIME
12V POWER-UP
MAX5946 toc15
MAX5946 toc14
3.3AUXO_
OUTPUT VOLTAGE
2V/div
12G_
20V/div
12V OUTPUT
10V/div
PWRGD
2V/div
12VIN, 12V INPUT
10V/div
AUXON_
2V/div
40ms/div
6
PWRGD_
5V/div
40ms/div
_______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
TURN-ON DELAY 3.3V OUTPUT AND
3.3V AUXILIARY OUTPUT
3.3V INPUT/3.3V AUXILIARY INPUT
POWER-UP
MAX5946 toc17
MAX5946 toc16
3.3G_
10V/div
5V/div
3.3VAUXO_
OUTPUT VOLTAGE
3.3V OUTPUT
5V/div
5V/div
3.3 INPUT,
3.3VAUXIN
3.3S_+
5V/div
5V/div
3.3 OUTPUT VOLTAGE
3.3VAUXO_
5V/div
5V/div
PWRGD
3.3G_
10V/div
PWRGD_
5V/div
100ms/div
4ms/div
FAULT CONDITION ON 12V OUTPUT
(AUTORESTART OPTION MAX5946A)
FAULT CONDITION ON 3.3V OUTPUT
(AUTORESTART OPTION MAX5946A)
MAX5946 toc19
MAX5946 toc18
RLOAD STEP TO 1.5Ω
tRESTART
12V OUTPUT CURRENT
5A/div
RLOAD STEP TO 0.5Ω
12G_
20V/div
3.3G_
10V/div
12V OUTPUT VOLTAGE
10V/div
3.3V OUTPUT VOLTAGE
5V/div
FAULT_
5V/div
tRESTART
FAULT_
5V/div
100ms/div
100ms/div
FAULT CONDITION ON AUXILIARY OUTPUT
(AUTORESTART OPTION MAX5946A)
FAULT CONDITION ON 12V OUTPUT
(LATCH OPTION MAX5946L)
MAX5946 toc20
RLOAD STEP TO 4Ω
3.3V MAIN OUTPUT CURRENT
2A/div
MAX5946 toc21
3.3VAUXO_ OUTPUT CURRENT
500mA/div
RLOAD STEP TO 1.5Ω
12V OUTPUT CURRENT
5A/div
12G_
20V/div
tRESTART
100ms/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
12V OUTPUT VOLTAGE
10V/div
FAULT_
2V/div
FAULT_
5V/div
100ms/div
_______________________________________________________________________________________
7
MAX5946
Typical Operating Characteristics (continued)
(V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical
Application Circuit.)
MAX5946
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical
Application Circuit.)
FAULT CONDITION ON 3.3V OUTPUT
(LATCH OPTION MAX5946L)
FAULT CONDITION ON 12V OUTPUT
MAX5946 toc23
MAX5946 toc22
tFAULT
RLOAD
STEP TO 1.5Ω
12V OUTPUT CURRENT
5A/div
RLOAD STEP TO 0.5Ω
12G_
20V/div
3.3G_
10V/div
12V OUTPUT VOLTAGE
10V/div
3.3V OUTPUT VOLTAGE
5V/div
FAULT_
5V/div
FAULT_
5V/div
100ms/div
4ms/div
FAULT CONDITION ON AUXILIARY OUTPUT
(LATCH OPTION MAX5946L)
FAULT CONDITION ON 3.3V MAIN OUTPUT
MAX5946 toc25
MAX5946 toc24
tFAULT
3.3V OUTPUT CURRENT
2A/div
RLOAD
STEP TO 0.5Ω
3.3V OUTPUT CURRENT
2A/div
RLOAD STEP TO 4Ω
3.3VAUXO_ OUTPUT CURRENT
500mA/div
3.3G_
10V/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
3.3V OUTPUT VOLTAGE
5V/div
FAULT_
2V/div
FAULT_
5V/div
100ms/div
4ms/div
SHORT CIRCUIT ON 12V OUTPUT
FAULT CONDITION ON AUXILIARY OUTPUT
MAX5946 toc27
MAX5946 toc26
tFAULT
RLOAD
STEP TO 4Ω
12V OUTPUT CURRENT
5A/div
3.3VAUXO_ OUTPUT CURRENT
500mA/div
12G_
20V/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
12V OUTPUT VOLTAGE
10V/div
FAULT_
2V/div
4ms/div
8
FAULT_
5V/div
2ms/div
_______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
SHORT CIRCUIT ON 12V OUTPUT
SHORT CIRCUIT ON 3.3V OUTPUT
MAX5946 toc28
MAX5946 toc29
3.3V OUTPUT CURRENT
2A/div
12V OUTPUT CURRENT
25A/div
12G_
20V/div
0V
12V OUTPUT VOLTAGE
10V/div
0V
3.3G_
5V/div
3.3V OUTPUT VOLTAGE
5V/div
FAULT_
5V/div
0V
4µs/div
FAULT_
5V/div
2ms/div
SHORT CIRCUIT ON 3.3AUXO_
SHORT CIRCUIT ON 3.3V OUTPUT
MAX5946 toc31
MAX5946 toc30
3.3VAUXO_ OUTPUT CURRENT
500mA/div
3.3V OUTPUT CURRENT
10A/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
3.3G_
5V/div
3.3V OUTPUT VOLTAGE
5V/div
FAULT_
5V/div
FAULT_
5V/div
0V
2ms/div
2µs/div
POWER-UP INTO FAULT
(AUXILIARY SUPPLY)
SHORT CIRCUIT ON 3.3VAUXO_
MAX5946 toc32
MAX5946 toc33
RLOAD = 4Ω
3.3VAUXO_ OUTPUT CURRENT
5A/div
tSU
3.3VAUXO_ OUTPUT CURRENT
500mA/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
AUXON_
5V/div
FAULT_
5V/div
2µs/div
FAULT_
5V/div
4ms/div
_______________________________________________________________________________________
9
MAX5946
Typical Operating Characteristics (continued)
(V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical
Application Circuit.)
MAX5946
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical
Application Circuit.)
POWER-UP INTO FAULT
(3.3V MAIN)
POWER-UP INTO FAULT
(12V OUTPUT)
MAX5946 toc34
MAX5946 toc35
RLOAD = 0.5Ω
3.3V OUTPUT CURRENT
4A/div
tSU
12V OUTPUT CURRENT
5A/div
tSU
3.3G_
5V/div
12G_
10V/div
3.3V OUTPUT VOLTAGE
2V/div
12V OUTPUT VOLTAGE
10V/div
ON_, AUXON_
5V/div
ON_, AUXON_
5V/div
FAULT_
5V/div
FAULT_
5V/div
4ms/div
4ms/div
PRESENT-DETECT (ON/OFF) OPERATION
PRESENT-DETECT (ON/OFF) OPERATION
MAX5946 toc36
MAX5946 toc37
12V OUTPUT VOLTAGE
10V/div
12V OUTPUT VOLTAGE
10V/div
5V/div
3.3VAUXO_
OUTPUT VOLTAGE
5V/div
3.3VAUXO_
OUTPUT VOLTAGE
5V/div
PWRGD
5V/div
PWRGD
5V/div
PRES-DET_
5V/div
PRES-DET_
40ms/div
4ms/div
FORCED-ON (ON/OFF) OPERATION
FORCED-ON (ON/OFF) OPERATION
MAX5946 toc38
12V OUTPUT VOLTAGE
10V/div
12V OUTPUT VOLTAGE
10V/div
5V/div
3.3VAUXO_
OUTPUT VOLTAGE
5V/div
3.3VAUXO_
OUTPUT VOLTAGE
5V/div
PWRGD
5V/div
PWRGD
5V/div
FON_
5V/div
FON_
40ms/div
10
MAX5946 toc39
4ms/div
______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
POWER-ON-RESET TIME
vs. PORADJ RESISTOR
DEBOUNCED ON/OFF OPERATION
tPOR_HL (ms)
INPUT_
2V/div
OUTPUT_
2V/div
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
600
400
200
0
MAX5946 toc41
MAX5946 toc40
0 100 200 300 400 500 600 700 800 900 1000
10ms/div
RPORADJ (kΩ)
tFAULT TIME DELAY vs. TIM RESISTOR
MAX5946 toc42
200
180
160
tFAULT (ms)
140
120
100
80
60
40
20
0
0 100 200 300 400 500 600 700 800 900 1000
RTIM (kΩ)
______________________________________________________________________________________
11
MAX5946
Typical Operating Characteristics (continued)
(V12VIN = V12SA+ = 12V, V3.3VAUXIN = V3.3S_+ = VON_ = VAUXON_ = VINPUT_ = 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, TA = +25°C, unless otherwise noted, see the Typical
Application Circuit.)
Dual PCI Express, Hot-Plug
Controller
MAX5946
Pin Description
PIN
12
NAME
FUNCTION
Present-Detect Input A. PRES-DETA accepts inputs from the PRSNT#2 pin on a PCI express connector.
PRES-DETA has an internal pullup to 3.3VAUXIN. When PRES-DETA is low, the outputs follow the
command from ONA and AUXONA after a 4ms debounced time. When PRES-DETA goes from low to
high, all outputs of the respective slot shut down with no delay (see Table 2).
1
PRES-DETA
2
FONA
Forced-On Input A. FONA has a 50kΩ internal pullup to 3.3VAUXIN. A logic-low on FONA turns on all
slot A outputs as long as the power inputs are within their operating range, regardless of the status of
the other input signals. Leave FONA open for normal operation (see Table 2).
3
ONA
Slot A 12V And 3.3V Outputs Enable. A logic-high at ONA turns on the 12V and 3.3V outputs of slot A
(see Table 2).
4
AUXONA
5
12SA+
Slot A 12V Positive Current-Sense Input. Connect the positive terminal of the current-sense resistor to
12SA+ using the Kelvin-sensing technique to assure accurate current sensing.
6
12SA-
Slot A 12V Negative Current-Sense Input. Connect 12SA- to the negative side of the current-sense
resistor using the Kelvin-sensing technique to assure accurate current sensing.
7
12GA
Slot A 12V Gate-Drive Output. Connect 12GA to the gate of slot A’s 12V MOSFET. At power-up, V12GA
is raised to the internal charge-pump voltage level by a constant current.
8
3.3SA+
Slot A 3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to
3.3SA+ using the Kelvin-sensing technique to assure accurate current sensing. This input is also used
for the 3.3V supply’s UVLO function.
9
3.3SA-
Slot A 3.3V Negative Current-Sense Input. Connect to the negative side of the sense resistor using the
Kelvin-sensing technique to assure accurate current sensing.
10
3.3GA
Slot A 3.3V Gate-Drive Output. Connect 3.3GA to the gate of slot A’s 3.3V MOSFET. At power-up, V3.3GA
is charged to 5.5V above the 3.3V supply by a constant current derived from V12VIN.
Slot A 3.3V Auxiliary Output Enable. A logic-high at AUXONA turns on the slot A auxiliary output
(3.3VAUXOA), see Table 2.
11
FAULTA
Open-Drain Fault Output Signal. FAULTA latches active low whenever the slot A outputs are shut down
due to a fault. A fault is either of:
• An overcurrent condition lasting longer than the overcurrent timeout.
• A device over temperature condition.
If the fault is detected in the main outputs, FAULTA must be reset by toggling the ONA input. If the fault
is in the auxiliary output, FAULTA must be reset by toggling both ONA and AUXONA. For the autorestart version, FAULTA is reset when the part initiates the next power-on cycle.
12
PWRGDA
Open-Drain Power-Good Output. PWRGDA goes low tPOR_HL after all outputs of slot A reach their final
value and the power MOSFETs are fully enhanced.
13
3.3VAUXOA
Slot A 3.3V Auxiliary Power-Supply Output
14
3.3VAUXIN
3.3V Auxiliary Supply Input. 3.3VAUXIN is the input to a charge pump that drives the internal MOSFETs
connecting 3.3VAUXIN to 3.3VAUXOA and 3.3VAUXOB. V3.3VAUXIN is also used to power the internal
control logic and analog references of the MAX5946.
15
3.3VAUXOB
Slot B 3.3V Auxiliary Power Output
16
PWRGDB
17
FAULTB
18
3.3GB
Slot B Power-Good Output. See PWRGDA function.
Slot B Open-Drain Fault Output. See FAULTA function.
Slot B 3.3V Gate-Drive Output. See 3.3GA function.
______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
PIN
NAME
FUNCTION
19
3.3SB-
Slot B 3.3V Negative Current-Sense Input. See 3.3SA- function.
20
3.3SB+
Slot B 3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to
3.3SB+ using the Kelvin-sensing technique to assure accurate current sensing.
21
12GB
Slot B 12V Gate-Drive Output. See 12GA function.
22
12SB-
Slot B 12V Negative Current-Sense Input. See 12SA- function.
23
12SB+
Slot B 12V Positive Current-Sense Input. See 12SA+ function.
24
AUXONB
25
ONB
26
FONB
27
PRES-DETB
28
TIM
Slot B 3.3V Auxiliary Output Enable. See AUXONA function.
Slot B 12V And 3.3V Outputs Enable. See ONA function.
Slot B Forced-On Input. See FONA function.
Slot B Present-Detect Input. See PRES-DETA function.
Overcurrent Timeout Programming Input. Connect a resistor between 500Ω and 500kΩ from TIM to GND
to program tFAULT. Leave TIM floating for a default timeout of 11ms.
29
INPUT2
30
OUTPUT2
Digital Logic Gate Input
31
OUTPUT1
32
INPUT1
33
12VIN
12V Supply Input. V12VIN drives the gates of the MOSFETs connected to 3.3GA and 3.3GB. 12VIN
powers an internal charge pump that drives the gates of the MOSFETs connected to 12GA and 12GB.
34
GND
Ground
35
PGND
36
PORADJ
Digital Output. 4ms debounced digital output of INPUT2.
Digital Output. 4ms debounced digital output of INPUT1.
Digital Logic Gate Input
Power Ground. Connect externally to GND.
Power-On-Reset Programming Input. Connect a resistor between 500Ω and 500kΩ from PORADJ to
GND to program the POR timing. Leave floating for a default value of 160ms.
Detailed Description
The MAX5946 dual hot-plug controller is designed for
PCI express applications. The device provides hot-plug
control for 12V, 3.3V, and 3.3V auxiliary supplies of two
PCI express slots. The MAX5946’s logic inputs/outputs
allow interfacing directly with the system hot-plug-management controller or through an SMBus with an external I/O expander. An integrated debounced attention
switch and present-detect signals are included to simplify system design.
The MAX5946 drives four external n-channel MOSFETs
to control the 12V and 3.3V main outputs. The 3.3V auxiliary outputs are controlled through internal 0.24Ω nchannel MOSFETs. Internal charge pumps provide a
gate drive for the 12V outputs while the gate drive of
the 3.3V output is driven by the 12V input supply. The
3.3V auxiliary outputs are completely independent from
the main outputs with their own charge pumps.
At power-up, the MAX5946 keeps all of the external
MOSFETs off until all supplies rise above their respective UVLO thresholds. The device keeps the internal
MOSFETs off only until the 3.3VAUXIN supply rises
above its UVLO threshold. Upon a turn-on command,
the MAX5946 enhances the external and internal
MOSFETs slowly with a constant gate current to limit
the power-supply inrush current. The MAX5946 actively
limits the current of all outputs at all times and shuts
down if an overcurrent condition persists for longer
than a programmable overcurrent timeout. Thermalprotection circuitry also shuts down all outputs if the die
temperature exceeds +150°C. After an overcurrent or
overtemperature fault condition, the MAX5946L latches
off while the MAX5946A automatically restarts after a
restart time delay.
The power requirement for PCI express connectors is
defined by the PCI express card specification and
summarized in Table 1.
______________________________________________________________________________________
13
MAX5946
Pin Description (continued)
MAX5946
Dual PCI Express, Hot-Plug
Controller
RTIM
RPORADJ
INPUT1
INPUT2
OUTPUT1
PWRGDA
FAULTA
12VIN
OUTPUT2
PORADJ
TIM
PWRGDB
FAULTB
12SB+
12SA+
RSENSE12A
54mV
+
-
+
-
500mV
500mV
CHARGE
PUMP
12SA-
+
-
+
-
54mV
RSENSE12B
CHARGE
PUMP
12SB5µA
5µA
12GA
10µA
150µA
12GB
Aµ01
10µA
tFAULT
OSCILLATOR
DEBOUNCE
tPOR
OSCILLATOR
FAST
OSCILLATOR
100mA
A µ0 0 1
100mA
150µA
MAX5946
3.3SA+
3.3SB+
100mV
RSENSE3.3A
20mV
+
-
+
-
+
-
100mV
+
-
RSENSE3.3B
20mV
3.3SA-
3.3SB5µA
50µA
3.3GA
3.3GB
BIAS
REFERENCES AND UVLO
10µA
A µ0 1
10µA
CONTROL LOGIC
MAIN-SLOT B
CONTROL LOGIC
MAIN-SLOT A
150µA
150mA
Aµ051
150mA
150µA
3.3VAUXIN
VREF
+
-
VREF
+
CHARGE
PUMP
CHARGE
PUMP
CONTROL LOGIC
AUX-SLOT B
CONTROL LOGIC
AUX-SLOT A
3.3VAUXOA
3.3VAUXOB
INPUT COMPARATORS AND CHIP-CONTROL LOGIC
PGND
GND
ONA
AUXONA
FONA
PRES-DETA
ONB
AUXONB
FONB
PRES-DETB
Figure 1. Functional Diagram
14
______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
POWER RAIL
X1 CONNECTOR
X4/8 CONNECTOR
X16 CONNECTOR
Voltage Tolerance
±9% (max)
±9% (max)
±9% (max)
Supply Current
3.0A (max)
3.0A (max)
3.0A (max)
1000µF (max)
1000µF (max)
1000µF (max)
Voltage Tolerance
±8% (max)
±8% (max)
±8% (max)
Supply Current
0.5A (max)
2.1A (max)
5.5A (max)
300µF (max)
1000µF (max)
2000µF (max)
MAX5946
Table 1. Power Requirements for PCI Express Connectors
3.3V
Capacitive Load
12V
Capacitive Load
3.3V AUXILIARY
Voltage Tolerance
Supply Current
±9% (max)
±9% (max)
±9% (max)
Wake Enabled
375mA (max)
375mA (max)
375mA (max)
375mA (max)
20mA (max)
20mA (max)
20mA (max)
Non-Wake Enabled,
Capacitive Load
150µF (max)
150µF (max)
150µF (max)
Table 2. Control Logic Truth Table
ON_
AUXON_
FON_
PRES-DET_
12V_ AND 3.3V_
OUTPUTS
3.3VAUXO_
AUXILIARY
OUTPUTS
X
X
Low
X
On
On
X
X
High
High
Off
Off
Low
Low
High
Low*
Off
Off
High
Low
High
Low*
On
Off
Low
High
High
Low*
Off
On
High
High
High
Low*
On
On
*PRES-DET_ high-to-low transition has a 4ms delay (tDEG).
Startup
The main supply outputs can become active only after
all the following events have occurred:
• V3.3VAUXIN is above its UVLO threshold
•
V 12VIN and V 3.3SA+ are both above their UVLO
threshold
•
ON_ is driven high
•
PRES-DET_ is low for more than 4ms
The auxiliary supply output is made available only after
the following events have occurred:
•
V3.3VAUXIN is above its UVLO threshold
•
AUXON_ is driven high
•
PRES-DET_ is low for more than 4ms
The FON_ input overrides all other control signals and
turns on the respective slot when driven low, as long as
the UVLO thresholds have been reached. Table 2 summarizes the logic conditions required for startup.
The auxiliary supply input powers the internal control
logic and analog references of the MAX5946, so the
main supplies cannot be enabled if V3.3VAUXIN is not
present.
When an output is enabled, a programmable startup
timer (tSU) begins to count the startup time duration.
The value of tSU is set to 2x the fault timeout period
(tFAULT). RTIM externally connected from TIM to GND
sets the duration of tFAULT.
______________________________________________________________________________________
15
MAX5946
Dual PCI Express, Hot-Plug
Controller
ON_
ON_, AUXON_
VON_,TH
VPGTH12
VPGTH3.3
12G_, 3.3G_
VON_,TH
12VO_, 3.3VO_
V12ILIM,TH
RSENSE
12G_
12V OUTPUT
CURRENT
3.3VAUXO_
3.3VAUXO_
VPGTH3.3AUX
PWRGD_
tPOR_HL
PWRGD_
3.3AUXIN
RISING
EDGE
FAULT_
3.3VAUXIN
RISING
EDGE
2 x tFAULT
FAULT_
PWRGD_ IS PULLED UP TO 3.3VAUXO_.
FAULT_ IS PULLED UP TO 3.3VAUXIN.
A FAULT ON THE 3.3V OUTPUT OR 3.3VAUXO_ OUTPUT PRODUCES SIMILAR RESULTS.
PWRGD_ IS PULLED UP TO 3.3.
FAULT_ IS PULLED UP TO 3.3AUXIN.
Figure 2. Power-Up Timing, No Fault
Figure 3. 12V Power-Up Timing (Turn-On into Output
Overcurrent/Short Circuit)
controller disengages both the 12V and 3.3V outputs for
the particular slot (see the Fault Management section).
3.3V Auxiliary Output Normal Operation
12G_
V12ILIM,TH
RSENSE
12V OUTPUT
CURRENT
PWRGD_
The auxiliary output current is internally monitored and
actively limited to the maximum current-limit value. An
overcurrent fault condition occurs when the output
current exceeds the overcurrent threshold for longer
then tFAULT. A fault on an auxiliary channel causes all
supplies of the affected channel to be disabled after a
programmable time period t FAULT (see the Fault
Management section).
Power-Good (PWRGD_)
tFAULT
FAULT_
PWRGD_ IS PULLED UP TO 3.3VAUXO_.
FAULT_ IS PULLED UP TO 3.3VAUXIN.
A FAULT ON THE 3.3V OUTPUT OR 3.3VAUXO_ OUTPUT PRODUCES SIMILAR RESULTS.
Figure 4. 12 Output Overcurrent/Short Circuit During Normal
Operation
12V and 3.3V Outputs Normal Operation
The MAX5946 monitors and actively limits the current of
the 12V and 3.3V outputs after the startup period. Each
output has its own overcurrent threshold. If any of the
monitored output currents rise above the overcurrent
threshold for a period tFAULT, FAULT_ asserts and the
16
Power-good (PWRGD_) is an open-drain output that
pulls low a time (tPOR_HL) after all of the outputs of the
respective slot are fully on. All outputs are considered
fully on when 3.3G_ has risen to VPGTH3.3, 12G_ has
risen to V PGTH12 , and V 3.3AUXO_ is less then
V PGTH3.3AUX . t POR_HL is adjustable from 2.5ms to
1.5s by connecting a resistor from PORADJ to GND.
See the Setting the Power-On-Reset Timeout Period
(tPOR) section.
Thermal Shutdown
When the die temperature goes above (TSD) +150°C, an
overtemperature fault occurs and the MAX5946 shuts
down all outputs. The device waits for the junction temperature to decrease below TSD - Hysteresis before entering
fault management (see the Fault Management section).
______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
•
A fault on a main output (12V or 3.3V) shuts down
both main outputs of the respective slot. The 3.3V
auxiliary is not affected.
•
A fault on the 3.3V auxiliary output shuts down all
three outputs of the respective slot.
The MAX5946A automatically restarts from a fault shutdown after the tRESTART period, while the MAX5946L
latches off. If an overcurrent fault occurred on a main
output, bring ON_ low for at least tRESET (100µs) and
high again to reset the fault and restart the outputs. If
the overcurrent fault occurred on an auxiliary output or
an overtemperature fault occurred, bring both ON_ and
AUXON_ low for a minimum of tRESET to reset the fault.
Bring ON_ and/or AUXON_ high again to restart the
respective outputs. As an extra protection, the
MAX5946L waits a minimum of tRESTART before it can
be restarted.
Debounced Logic Gate
(Input_ and Output_)
INPUT1 and INPUT2 accept inputs from mechanical
switches. The corresponding outputs are OUTPUT1
and OUTPUT2. OUTPUT_ is debounced for 4ms. When
INPUT_ goes from high to low, OUTPUT_ goes low right
away and stays low for at least 4ms. After the
debounce time OUTPUT_ follows INPUT_. If INPUT_
goes from low to high, OUTPUT_ goes high right away
and stays high for at least 4ms. After the debounce
time, OUTPUT_ follows INPUT_. Figure 5 shows the timing diagram describing the INPUT_/OUTPUT_
debounced feature.
Present-Detect and Forced-On Inputs
(PRES-DET_, FON_)
PRES-DETA and PRES-DETB inputs detect the
PRSNT#2 pin on a PCI express connector. When the
card is plugged in, PRES-DET_ goes low and allows
the turn-on of the outputs of the respective slot after a
INPUT
tDBC
tDBC
tDBC
DEBOUNCED
OUTPUT
4ms debounced time. When the card is removed, an
internal 50kΩ pullup forces PRES-DET_ high and the
respective slot is shut down with no delay. PRES-DET_
works in conjunction with ON_ and VAUXON_ and only
enables the device when ON_ and VAUXON_ are high.
A logic-low on FON_ forces the respective slot (main
supplies and auxiliary) to turn on regardless of the status of the other logic inputs provided the UVLO thresholds are exceeded on all of the inputs.
Active Current Limits
Active current limits are provided for all three outputs of
slot A and slot B. Connect a current-sense resistor
between 12S_+ and 12S_- to set the current limit for the
12V outputs. The current limit is set to 54mV/RSENSE12.
RSENSE12 is either R1 or R3 in the Typical Application
Circuit. Connect a current-sense resistor between
3.3S_+ and 3.3S_- to set the current limit for the 3.3V
main outputs to 20mV/RSENSE3.3. RSENSE3.3 is either R2
or R4 in the Typical Application Circuit. For the auxiliary
output (3.3VAUXO_) the current limit is fixed at 470mA.
When the voltage across R SENSE12 or R SENSE3.3
reaches the current-limit threshold voltage, the
MAX5946 regulates the gate voltage to maintain the
current-limit threshold voltage across the sense resistor. If the current limit lasts for tFAULT then an overcurrent fault occurs. The MAX5946_ shuts down both the
12V and 3.3V outputs and asserts the FAULT_ output of
the respective slot.
When the auxiliary output reaches the current limit
(470mA) for longer then tFAULT, a fault occurs and the
device shuts down all outputs and asserts FAULT of the
respective slot.
Undervoltage Lockout Threshold
The UVLO thresholds prevent the internal auxiliary
MOSFETs and the external main channel MOSFETs
(Q1–Q4 in the Typical Application Circuit) from turning
on if V12VIN, V3.3VIN, and V3.3VAUXIN are not present.
Internal comparators monitor the main supplies and the
auxiliary supply and keep the gate-drive outputs
(12GA, 12GB, 3.3GA, and 3.3GB) low until the supplies
rise above their UVLO threshold. The 12V main supply
is monitored at 12VIN and has a UVLO threshold of
10V. The 3.3V main supply is monitored at 3.3SA+ and
has a UVLO threshold of 2.65V. The auxiliary supply is
monitored at 3.3VAUXIN and has a 2.65V UVLO threshold. For either main channel to operate, V3.3VAUXIN
must be above its UVLO threshold.
Figure 5. INPUT_ and OUTPUT_ Debounced Feature
______________________________________________________________________________________
17
MAX5946
FAULT Management
A fault occurs when an overcurrent lasts longer then
tFAULT or when the device experiences an overtemperature condition.
MAX5946
Dual PCI Express, Hot-Plug
Controller
SHUT DOWN
12V AND 3.3V OUTPUTS.
ASSERT FAULT_
STAY WAITING FOR
tRESTART
Y
HAS tFAULT
ELAPSED?
WAS CURRENT
LIMIT DETECTED ON ANY
12V OR
3.3V OUTPUT?
Y
START COUNTING
tFAULT
12V AND 3.3V
OUTPUTS
ARE ENABLED
N
N
IS FAULT STILL
PRESENT?
Y
N
RESET tFAULT
COUNTER
Y
N
LATCH-OFF
OPTION?
RESET FAULT_
AND
RESTART 12V, 3.3V
SUPPLIES
STAY WAITING FOR
ON_ TRANSITION
HIGH->LOW->HIGH
N
ENABLE CHARGE ON
12G_ AND 3.3G_
PINS. START
COUNTING tSU
POWER-ON MAIN
SUPPLIES FAULT
AND PWRGD ARE
HIGH IMPEDANCE
3.3AUXIN IS ON
AND ABOVE UVLO
Y
HAS tSU
ELAPSED?
ARE PWRGD
THRESHOLDS
REACHED?
RESET
PWRGD_
AFTER tPOR_LH DELAY
N
Y
STAY WAITING FOR BOTH
ON_ AND AUXON_
TRANSITION
HIGH->LOW->HIGH
RESET FAULT_
AND
RESTART ALL SUPPLIES
ASSERT
PWRGD_
AFTER tPOR_HL DELAY
N
Y
LATCH-OFF
OPTION?
POWER-ON AUXILIARY
SUPPLIES FAULT
AND PWRGD ARE
HIGH IMPEDANCE
N
SHUT DOWN
ALL OUTPUTS,
ASSERT FAULT_,
STAY WAITING FOR
tRESTART ELAPSED.
Y
ENABLE CHARGE ON
INTERNAL AUXILIARY
MOSFET, BEGIN
COUNTING tSU
IS tFAULT
ELAPSED?
START COUNTING
tFAULT
HAS tSU ELAPSED?
Y
AUX SUPPLY OUTPUT
IS ENABLED
N
N
IS FAULT STILL
PRESENT?
WAS CURRENT LIMIT
DETECTED ON AUXILIARY
OUTPUT?
Y
Y
N
RESET tFAULT
COUNTER
Figure 6. Fault Management Flow Chart
18
______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
The gate drive for the external MOSFETs is provided at
12GA, 12GB, 3.3GA, and 3.3GB. 12G_ is the gate drive
for the 12V main supply and is boosted to 5.3V above
V12VIN by an internal charge pump. During turn-on,
12G_ sources 5µA into the external gate capacitance to
control the turn-on time of the external MOSFET. During
turn-off, 12G_ sinks 150µA from the external gate
capacitance to quickly turn off the external MOSFET.
During short-circuit events, an internal 100mA current
activates to rapidly bring the load current into the regulation limits.
3.3G_ is the gate drive for the 3.3V main supply’s
MOSFET and is driven to 5.5V above the 3.3V main supply. The power for 3.3G_ is supplied from 12VIN and
has no internal charge pump. During turn-on, 3.3G_
sources 5µA into the external gate capacitance to control the turn-on time of the external MOSFET. During
turn-off, 3.3G_ sinks 150µA to quickly turn off the external MOSFET. During short-circuit events, an internal
150mA current activates to rapidly turn off the appropriate external MOSFET.
Auxiliary Supply (3.3VAUXIN)
3.3VAUXIN provides power to the auxiliary outputs as
well as the internal logic and references. The drains of
the internal auxiliary MOSFETs connect to 3.3VAUXIN
through internal sense resistors and the sources connect to the auxiliary outputs (3.3VAUXOA and
3.3VAUXOB). Both MOSFETs have typical on-resistance
of 0.3Ω. An internal charge pump boosts the gate-drive
voltage to fully turn on the internal n-channel MOSFETs.
The auxiliary supplies have an internal current limit set
to 470mA.
Applications Information
Setting the Fault Timeout Period (tFAULT)
tFAULT is the time an overcurrent or overtemperature
fault must remain for the MAX5946 to disable the main
or auxiliary channels of a particular slot. Program the
fault timeout period (tFAULT) by connecting a resistor
(RTIM) from TIM to GND. tFAULT can be calculated by
the following equation:
tFAULT = 166ns / Ω x RTIM
The tFAULT programmed time duration must be chosen
according to the total capacitance load connected to
the 12G_ and 3.3G_ pins. To properly power-up the
main supply outputs, the following constraints need to
be taken:
V
× CLOAD
t SU ≥ GATE
ICHG
where tSU = 2 x tFAULT and where
1) ICHG = 5µA.
2) V GATE = 18.4V for 12G_ and V GATE = 9.4V for
3.3G_.
3) CLOAD is the total capacitance load at the gate.
Maximum and minimum values for RTIM are 500Ω and
500kΩ, respectively. Leave TIM floating for a default
tFAULT of 11ms.
Setting the Power-On-Reset
Timeout Period (tPOR_HL)
tPOR_HL is the time from when the gate voltages of all
outputs of a slot reach their power-good threshold to
when PWRGD_ pulls low. Program the power-on-reset
timeout period (tPOR) by connecting a resistor (RPORADJ) from PORADJ to GND. tPOR_HL can be calculated by the following equation:
tPOR_HL = 2.5µs / Ω x RPORADJ
Maximum and minimum values for RPORADJ are 500Ω
and 500kΩ, respectively. Leave PORADJ floating for a
default tPOR of 160ms.
Component Selection
Select the external n-channel MOSFET according to the
applications current requirement. Limit the switch
power dissipation by choosing a MOSFET with an
RDS_ON low enough to have a minimum voltage drop at
full load. High RDS_ON causes larger output ripple if
there are pulsed loads. High RDS_ON can also trigger
an external undervoltage fault at full load. Determine
the MOSFETs power rating requirement to accommodate a short-circuit condition on the board during startup. Table 3 lists MOSFETs and sense resistor
manufacturers.
Additional External Gate
External capacitance can be added from the gate of
the external MOSFETs to GND to slow down the dV/dt
of the 12V and 3.3V outputs.
Maximum Load Capacitance
Large capacitive loads at the 12V output, the 3.3V output, and the 3.3V auxiliary output can cause a problem
when inserting discharged PCI cards into live backplanes. A fault occurs if the time needed to charge the
capacitance of the board is greater than the typical
startup time (2 x tFAULT). The MAX5946 can withstand
______________________________________________________________________________________
19
MAX5946
External MOSFET Gate Drivers
(12GA, 12GB, 3.3GA, and 3.3GB)
MAX5946
Dual PCI Express, Hot-Plug
Controller
Table 3. Component Manufacturers
COMPONENT
MANUFACTURER
PHONE
Vishay-Dale
402-564-3131
www.vishay.com
IRC
704-264-8861
www.irctt.com
Sense Resistor
MOSFETs
WEBSITE
Fairchild
888-522-5372
www.fairchildsemi.com
International Rectifier
310-322-3331
www.irf.com
Motorola
602-244-3576
www.mot-sps.com/ppd/
Vishay-Siliconix
—
large capacitive loads due to their adjustable startup
times and adjustable current-limit thresholds. Calculate
the maximum load capacitance as follows:
t
×I
CLOAD < SU LIM
VOUT
VOUT is either the 3.3V output, the 12V output, or the
3.3V auxiliary output for slot A or slot B.
www.vishay.com
thresholds before startup can occur. Input transients
can cause the input voltage to sag below the UVLO
threshold. The MAX5496 rejects transients on the input
supplies that are shorter than 4µs typical.
Chip Information
TRANSISTOR COUNT: 10,487
PROCESS: BiCMOS
Input Transients
The 12V input (12VIN), the 3.3V input (3.3SA+), and the
3.3V auxiliary (3.3VAUXIN) must be above their UVLO
20
______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
V12VIN
PCI EXPRESS
SLOT A
PCI EXPRESS
SLOT B
ADD-IN
CARD
IN5819
Q1
SI7448DP-T1
PRSNT1
V3.3AUXIN
R1
8mΩ
Q3
SI7448DP-T1
R3
8mΩ
PRSNT1
+12V
+12V
PWRGD
12GB
12SB+
12VIN
3.3VAUXIN
12SA+
12SA-
12GA
GND
112SB-
1µF
0.1µF
GND
PWRGD
PWRGDB
PWRGDA
10kΩ
10kΩ
MAX5946
3.3VAUX
3.3VAUXOA
3.3VAUX
3.3VAUXOB
RPORADJ = OPEN
3.3SB-
3.3SB+
TIM
PRES-DETB
OUTPUT1 / OUTPUT2
INPUT1 / INPUT2
ONA / ONB
AUXONA / AUXONB
FONA / FONB
FAULTA / FAULTB
PRES-DETA
3.3SA+
3.3SA-
3.3GA
3.3GB
PORADJ
GND
RTM =
OPEN
Q2
SI7448DP-T1
2
R2
5mΩ
2
R4
5mΩ
V3.3AUXIN
2
2
0.1µF
PRSNT2
10kΩ
MAX7313ATG
16-BIT I/O EXPANDER
MRL
LED's
2
3.3V INPUT
ATTENTION
SWITCHES
2
PRSNT2
Q4
SI7448DP-T1
+3.3V
+3.3V
MRL
2
2
2
LED's
3
SMBus
AO-2
INT
______________________________________________________________________________________
21
MAX5946
Typical Application Circuit
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.)
36L,40L, QFN.EPS
MAX5946
Dual PCI Express, Hot-Plug
Controller
22
______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
U
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 ____________________ 23
© 2004 Maxim Integrated Products
Printed USA
is a registered trademark of Maxim Integrated Products.
MAX5946
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.)