MAX5946LETX [MAXIM]
Dual PCI Express, Hot-Plug Controller; 双通道的PCI Express ，热插拔控制器
| 型号： | MAX5946LETX |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | Dual PCI Express, Hot-Plug Controller |
| 文件： | 总23页 (文件大小：1016K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-3483; Rev 0; 11/04
Dual PCI Express, Hot-Plug
Controller
General Description
Features
♦ PCI Express Compliant
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/out-
puts allow interfacing directly with the system hot-plug
management controller or through an SMBus™ with an
external I/O expander. An integrated debounced atten-
tion switch and present-detect signals are included to
simplify system design.
♦ 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
The MAX5946 drives four external n-channel MOSFETs
to control the 12V and 3.3V main outputs. The 3.3V aux-
iliary 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.
♦ 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
At power-up, the MAX5946 keeps all of the external
MOSFETs off until the supplies rise above their respec-
tive 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 automatical-
ly restarts after a restart time delay. The device is avail-
able in a 36-pin (6mm × 6mm) thin QFN package and
operates over the -40°C to +85°C temperature range.
♦ Allows Control through SMBus with an I/O
Expander
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
36 Thin QFN
36 Thin QFN
MAX5946AETX
MAX5946LETX
Pin Configuration
TOP VIEW
30 29 28
36 35 34 33 32 31
Applications
1
2
3
4
5
6
7
8
9
27
26
25
24
23
PRES-DETA
FONA
PRES-DETB
FONB
Servers
ONA
ONB
Desktop Mobile Server Platforms
Workstations
AUXONA
12SA+
12SA-
AUXONB
12SB+
MAX5946
22 12SB-
Embedded Devices
21
20
19
12GA
12GB
3.3SA+
3.3SA-
3.3SB+
3.3SB-
13 14 15 16 17 18
10 11 12
Typical Application Circuit appears at end of data sheet.
SMBus is a trademark of Intel Corp.
PCI Express is a trademark of PCI-SIG Corp.
THIN QFN
________________________________________________________________ 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.
Dual PCI Express, Hot-Plug
Controller
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
All Other Pins to GND......................-0.3V to (V
+ 0.3V)
3.3VAUXIN
12VIN......................................................................-0.3V to +14V
Continuous Power Dissipation (T = +70°C)
A
12GA, 12GB ..............................................-0.3V to (V
12SA+, 12SA-, 12SB+, 12SB-,
+ 6V)
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
12VIN
3.3GA, 3.3GB .....................................-0.3V to (V
+ 0.3V)
12VIN
3.3VAUXIN, ONA, ONB, FAULTA, FAULTB ............-0.3V to +6V
PWRGDA, PWRGDB ................................................-0.3V to +6V
PGND ....................................................................-0.3V to +0.3V
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
(V
12VIN
= V
= V
= 12V, V
= V
= V
= V
= V
= V
= 3.3V, PWRGD_ = FAULT_ = PORADJ
12S_-
12S_+
3.3S_+
3.3S_-
3.3VAUXIN
ON_
AUXON_
FON__
= TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, T = -40°C to +85°C, unless otherwise noted.
A
Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
12V SUPPLY
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
12V Supply Voltage Range
V
10.8
9.5
12
10
13.2
10.5
V
V
12VIN
V12VIN rising
Hysteresis
12VIN Undervoltage Lockout
V
12UVLO
0.1
0.5
12VIN Supply Current
I
V
= 13.2V
1
mA
12VIN
12VIN
12VIN CONTROL
12VIN Current-Limit
V
49
54
59
mV
12ILIM
Threshold (V
- V
)
12S_+
12S_-
12G_ Gate Charge Current
I
V
= GND
4
5
6
µA
µA
12G_CHG
12G_
Normal turn-off, ON_ = GND, V
_ = 2V
12G
50
150
250
12G_ Gate Discharge Current
I
12G_DIS
Output short-circuit condition, strong gate pulldown
to regulation, V - V ≥ 1V, V = 5V
50
4.8
-3.0
120
5.3
-4
180
5.8
mA
V
12VIN
12S_
12G_
12G_ Gate High Voltage
V
I
= 1µA
12G_H
12G_
(V
12G_
- V
)
12VIN
12G_ Threshold Voltage For
PWRGD_ Assertion (Note 2)
V
Referred to V
, I = 1µA
12VIN 12G_
-4.8
V
PGTH12
12S_- Input Bias Current
12S_+ Input Bias Current
3.3V SUPPLY
1
µA
µA
20
60
V
V
,
3.3SA+
3.3V Supply Voltage Range
3.0
3.3
3.6
V
3.3SB+
3.3SA+ rising
Hysteresis
2.52
2.65
30
2.78
V
Undervoltage Lockout
(Note 3)
mV
2
_______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
12VIN
= V
= V
= 12V, V
= V
= V
= V
= V
= V
= 3.3V, PWRGD_ = FAULT_ = PORADJ
12S_-
12S_+
3.3S_+
3.3S_-
3.3VAUXIN
ON_
AUXON_
FON__
= TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, T = -40°C to +85°C, unless otherwise noted.
A
Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
3.3V CONTROL
3.3V Current-Limit Threshold
(V - V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
17
20
23
mV
3.3ILIM
)
3.3S_-
3.3S_+
3.3G_ Gate Charge Current
I
V
= GND
3.3G_
4
5
6
µA
µA
3.3G_CHG
ON_ = GND, V
= 2V
50
150
250
3.3G_
3.3G_ Gate Discharge
Current
I
3.3G_DIS
Output short-circuit condition, strong gate pulldown
to regulation, V
100
4.5
150
5.5
-4
220
6.8
mA
V
- V
3.3S_
≥ 1V, V
= 5V
3.3G_
3.3S_+
3.3G_ Gate High Voltage
V
Sourcing 1µA
3.3G_H
(V
3.3G_
- V
)
3.3S_+
3.3G_ Threshold Voltage For
PWRGD_ Assertion (Note 2)
V
Referred to V
, I = 1µA
3.3VAUXIN 3.3G_
-3.0
-4.5
V
PGTH3.3
3.3S_- Input Bias Current
3.3S_+ Input Bias Current
3.3V AUXILIARY SUPPLY
1
µA
µA
20
60
3.3VAUXIN Supply Voltage
Range
V
3.0
3.3
3.6
V
3.3VAUXIN
3.3VAUXIN rising
Hysteresis
2.52
2.65
30
2.78
V
3.3VAUXIN Undervoltage
Lockout
V
3.3VAUXUVLO
mV
mA
3.3VAUXIN Supply Current
V
= 3.6V
1.5
3
3.3VAUXIN
3.3VAUXIN to 3.3VAUXO_
Maximum Dropout
I
= 375mA
225
mV
mA
3.3VAUXO_
3.3VAUXO_ Current-Limit
Threshold
3.3VAUXO_ shorted to GND
376
470
564
400
3.3VAUXO_ Threshold For
PWRGD_ Assertion
V
mV
PGTH3.3AUX
(V
- V
)
3.3VAUXO_
3.3VAUXIN
(Note 3)
LOGIC SIGNALS
Input-Logic Threshold
(ON_, FON_, AUXON_,
PRES-DET_, INPUT_)
Rising edge
Hysteresis
1.0
25
2.0
V
25
mV
Input Bias Current
(ON_, AUXON_, INPUT_)
1
µA
kΩ
µs
FON_, PRES-DET_ Internal
Pullup
50
4
75
ON_, AUXON_ High-to-Low
Deglitch Time
_______________________________________________________________________________________
3
Dual PCI Express, Hot-Plug
Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
12VIN
= V
= V
= 12V, V
= V
= V
= V
= V
= V
= 3.3V, PWRGD_ = FAULT_ = PORADJ
12S_-
12S_+
3.3S_+
3.3S_-
3.3VAUXIN
ON_
AUXON_
FON__
= TIM = OUTPUT_ = 12G_ = 3.3G_ = OPEN, INPUT_ = PRES_DET_ = PGND = GND, T = -40°C to +85°C, unless otherwise noted.
A
Typical values are at T = +25°C.) (Note 1)
A
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
PRES-DET_ High-to-Low
Deglitch Time
t
3
5
7
ms
DEG
PORADJ = open
90
35
160
55
250
75
R
R
R
= 20kΩ
PWRGD_ Power-On Reset
Time (Note 2)
PORADJ
PORADJ
PORADJ
t
t
ms
POR_HL
POR_LH
= 100kΩ
= 200kΩ
145
265
570
380
PWRGD_ Low-to-High
Deglitch Time
4
µs
V
Sinking 2mA
Sinking 30mA
0.1
0.7
PWRGD_, FAULT_ Output
Low Voltage
PWRGD_, FAULT_ Output-
High Leakage Current
V
= V
= 5.5V
FAULT_
1
µA
PWRGD_
TIM = open
5.5
1.4
12
11
2.6
22
59
17.0
3.8
32
R
TIM
R
TIM
R
TIM
= 15kΩ
FAULT_ Timeout
t
ms
FAULT
= 120kΩ
= 300kΩ
FAULT_ Timeout During
Startup
t
2 x t
ms
ms
µs
°C
°C
ms
V
SU
FAULT
Autorestart Delay Time
t
64 x t
FAULT
RESTART
Fault Reset Minimum Pulse
Width (Note 4)
t
100
RESET
Thermal-Shutdown Threshold
T
T rising
J
+150
20
SD
Thermal-Shutdown Threshold
Hysteresis
OUTPUT_ Debounce Time
OUTPUT_ High Voltage
OUTPUT_ Low Voltage
t
2.6
4.4
6.2
DBC
V
3.3VAUXIN
- 0.3
Sourcing 2mA
Sinking 2mA
V
3.3VAUXIN
0.4
V
Note 1: 100% production tested at T = +25°C. Parameters over temperature are guaranteed by design.
A
Note 2: PWRGD_ asserts a time t
after V
, V
, and V
conditions are met.
POR_HL
PGTH12 PGTH3.3
PGTH3.3AUX
Note 3: The UVLO for the 3.3V supply is sensed at 3.3SA+.
Note 4: This is the time that ON_ or AUXON_ must stay low when resetting a fault condition.
4
_______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics
(V
= V
= 12V, V
= V
= V
= V
= V
= 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
INPUT_
12VIN
12SA+
3.3VAUXIN
3.3S_+
ON_
AUXON_
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, T = +25°C, unless otherwise noted, see the Typical
A
Application Circuit.)
ON AND AUXON LOW-TO-HIGH THRESHOLD
VOLTAGE vs. TEMPERATURE
12VIN INPUT SUPPLY CURRENT
vs. TEMPERATURE
3.3VAUXIN SUPPLY CURRENT
vs. TEMPERATURE
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
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
2.0
1.8
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
ON_ OR AUXON_
-40
-15
10
35
60
85
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
12G_ AND 3.3G_ GATE CHARGE
CURRENT vs. TEMPERATURE
12G_ AND 3.3G_ GATE DISCHARGE
CURRENT vs. TEMPERATURE
3.3VAUXO_ OUTPUT VOLTAGE vs. CURRENT
3.5
5.35
5.30
5.25
5.20
5.15
5.10
5.05
5.00
4.95
4.90
4.85
170
165
160
155
150
145
3.0
2.5
2.0
1.5
1.0
0.5
0
12G_
3.3G_
12G_
3.3G_
0
0.1
0.2
0.3
0.4
0.5
0.6
-40
-15
10
35
60
85
-40
-15
10
35
60
85
OUTPUT CURRENT (A)
TEMPERATURE (°C)
TEMPERATURE (°C)
3.3VAUX INTERNAL SWITCH
MAXIMUM DROPOUT vs. TEMPERATURE
12V AND 3.3V CURRENT-LIMIT THRESHOLD
VOLTAGE vs. TEMPERATURE
60
AUXILIARY CURRENT LIMIT
vs. TEMPERATURE
0.20
0.18
0.16
0.14
0.12
0.10
0.08
0.06
0.04
0.02
0
0.500
0.495
0.490
0.485
0.480
0.475
0.470
0.465
0.460
0.455
0.450
AUXILIARY OUTPUT CURRENT = 375mA
50
40
30
20
10
0
12V CURRENT-SENSE
THRESHOLD
3.3V CURRENT-SENSE
THRESHOLD
-40
-15
10
35
60
85
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V
= V
= 12V, V
= V
= V
= V
= V
= 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
INPUT_
12VIN
12SA+
3.3VAUXIN
3.3S_+
ON_
AUXON_
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, T = +25°C, unless otherwise noted, see the Typical
A
Application Circuit.)
12VIN UNDERVOLTAGE LOCKOUT
THRESHOLD vs. TEMPERATURE
3.3VAUXIN UNDERVOLTAGE LOCKOUT
THRESHOLD vs. TEMPERATURE
10.20
10.15
10.10
10.05
10.00
9.95
2.70
2.68
2.66
2.64
2.62
2.60
9.90
9.85
9.80
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
12V TURN-ON/OFF TIME
3.3V TURN-ON/OFF TIME
MAX5946 toc13
MAX5946 toc12
3.3V OUTPUT
5V/div
12V OUTPUT
10V/div
3.3G_
10V/div
12G_
20V/div
ON_
ON_
5V/div
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
PWRGD_
5V/div
40ms/div
40ms/div
6
_______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V
= V
= 12V, V
= V
= V
= V
= V
= 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
INPUT_
12VIN
12SA+
3.3VAUXIN
3.3S_+
ON_
AUXON_
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, T = +25°C, unless otherwise noted, see the Typical
A
Application Circuit.)
TURN-ON DELAY 3.3V OUTPUT AND
3.3V INPUT/3.3V AUXILIARY INPUT
3.3V AUXILIARY OUTPUT
POWER-UP
MAX5946 toc17
MAX5946 toc16
3.3G_
10V/div
3.3VAUXO_
OUTPUT VOLTAGE
5V/div
3.3V OUTPUT
5V/div
3.3 INPUT,
3.3VAUXIN
5V/div
5V/div
3.3S_+
5V/div
3.3 OUTPUT VOLTAGE
PWRGD
3.3VAUXO_
5V/div
5V/div
3.3G_
10V/div
PWRGD_
5V/div
4ms/div
100ms/div
FAULT CONDITION ON 3.3V OUTPUT
FAULT CONDITION ON 12V OUTPUT
(AUTORESTART OPTION MAX5946A)
(AUTORESTART OPTION MAX5946A)
MAX5946 toc19
MAX5946 toc18
R STEP TO 0.5Ω
LOAD
R
STEP TO 1.5Ω
LOAD
3.3V MAIN OUTPUT CURRENT
2A/div
12V OUTPUT CURRENT
5A/div
3.3G_
10V/div
12G_
20V/div
3.3V OUTPUT VOLTAGE
5V/div
12V OUTPUT VOLTAGE
10V/div
t
t
RESTART
FAULT_
5V/div
RESTART
FAULT_
5V/div
100ms/div
100ms/div
FAULT CONDITION ON AUXILIARY OUTPUT
FAULT CONDITION ON 12V OUTPUT
(LATCH OPTION MAX5946L)
(AUTORESTART OPTION MAX5946A)
MAX5946 toc20
MAX5946 toc21
R
STEP TO 4Ω
R
STEP TO 1.5Ω
LOAD
LOAD
3.3VAUXO_ OUTPUT CURRENT
500mA/div
12V OUTPUT CURRENT
5A/div
12G_
20V/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
12V OUTPUT VOLTAGE
10V/div
t
RESTART
FAULT_
2V/div
FAULT_
5V/div
100ms/div
100ms/div
_______________________________________________________________________________________
7
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V
= V
= 12V, V
= V
= V
= V
= V
= 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
INPUT_
12VIN
12SA+
3.3VAUXIN
3.3S_+
ON_
AUXON_
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, T = +25°C, unless otherwise noted, see the Typical
A
Application Circuit.)
FAULT CONDITION ON 3.3V OUTPUT
(LATCH OPTION MAX5946L)
FAULT CONDITION ON 12V OUTPUT
MAX5946 toc23
MAX5946 toc22
R
LOAD
R
STEP TO 0.5Ω
LOAD
STEP TO 1.5Ω
3.3V OUTPUT CURRENT
2A/div
12V OUTPUT CURRENT
5A/div
t
FAULT
3.3G_
10V/div
12G_
20V/div
3.3V OUTPUT VOLTAGE
5V/div
12V OUTPUT VOLTAGE
10V/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
R
STEP TO 4Ω
LOAD
3.3VAUXO_ OUTPUT CURRENT
500mA/div
3.3V OUTPUT CURRENT
2A/div
R
LOAD
STEP TO 0.5Ω
t
FAULT
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
R
LOAD
STEP TO 4Ω
12V OUTPUT CURRENT
5A/div
3.3VAUXO_ OUTPUT CURRENT
500mA/div
t
FAULT
12G_
20V/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
12V OUTPUT VOLTAGE
10V/div
FAULT_
2V/div
FAULT_
5V/div
2ms/div
4ms/div
8
_______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V
= V
= 12V, V
= V
= V
= V
= V
= 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
INPUT_
12VIN
12SA+
3.3VAUXIN
3.3S_+
ON_
AUXON_
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, T = +25°C, unless otherwise noted, see the Typical
A
Application Circuit.)
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
3.3G_
5V/div
12V OUTPUT VOLTAGE
10V/div
0V
3.3V OUTPUT VOLTAGE
5V/div
FAULT_
5V/div
0V
FAULT_
5V/div
4µs/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
R
= 4Ω
LOAD
3.3VAUXO_ OUTPUT CURRENT
5A/div
3.3VAUXO_ OUTPUT CURRENT
500mA/div
t
SU
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
3.3VAUXO_ OUTPUT VOLTAGE
2V/div
AUXON_
5V/div
FAULT_
5V/div
FAULT_
5V/div
2µs/div
4ms/div
_______________________________________________________________________________________
9
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V
= V
= 12V, V
= V
= V
= V
= V
= 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
INPUT_
12VIN
12SA+
3.3VAUXIN
3.3S_+
ON_
AUXON_
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, T = +25°C, unless otherwise noted, see the Typical
A
Application Circuit.)
POWER-UP INTO FAULT
(3.3V MAIN)
POWER-UP INTO FAULT
(12V OUTPUT)
MAX5946 toc34
MAX5946 toc35
R
= 0.5Ω
LOAD
3.3V OUTPUT CURRENT
4A/div
12V OUTPUT CURRENT
5A/div
t
t
SU
SU
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
12V OUTPUT VOLTAGE
10V/div
10V/div
3.3VAUXO_
OUTPUT VOLTAGE
3.3VAUXO_
OUTPUT VOLTAGE
5V/div
5V/div
5V/div
5V/div
PWRGD
PWRGD
PRES-DET_
PRES-DET_
5V/div
5V/div
40ms/div
4ms/div
FORCED-ON (ON/OFF) OPERATION
FORCED-ON (ON/OFF) OPERATION
MAX5946 toc38
MAX5946 toc39
12V OUTPUT VOLTAGE
10V/div
12V OUTPUT VOLTAGE
10V/div
3.3VAUXO_
OUTPUT VOLTAGE
3.3VAUXO_
OUTPUT VOLTAGE
5V/div
5V/div
5V/div
5V/div
PWRGD
FON_
PWRGD
FON_
5V/div
5V/div
40ms/div
4ms/div
10 ______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V
= V
= 12V, V
= V
= V
= V
= V
= 3.3V, PRES-DET_ = GND, FON_ = PORADJ = TIM =
INPUT_
12VIN
12SA+
3.3VAUXIN
3.3S_+
ON_
AUXON_
float, FAULT_ = 10kΩ to 3.3VAUXIN, PWRGDA = 10kΩ to 3.3VAUXO_, T = +25°C, unless otherwise noted, see the Typical
A
Application Circuit.)
POWER-ON-RESET TIME
vs. PORADJ RESISTOR
DEBOUNCED ON/OFF OPERATION
MAX5946 toc40
3000
2800
2600
2400
2200
2000
1800
1600
1400
1200
1000
800
INPUT_
2V/div
OUTPUT_
2V/div
600
400
200
0
0
100 200 300 400 500 600 700 800 900 1000
10ms/div
R
(kΩ)
PORADJ
t
TIME DELAY vs. TIM RESISTOR
FAULT
200
180
160
140
120
100
80
60
40
20
0
0
100 200 300 400 500 600 700 800 900 1000
(kΩ)
R
TIM
______________________________________________________________________________________ 11
Dual PCI Express, Hot-Plug
Controller
Pin Description
PIN
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
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).
2
FONA
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).
3
4
5
6
7
ONA
AUXONA
12SA+
12SA-
Slot A 3.3V Auxiliary Output Enable. A logic-high at AUXONA turns on the slot A auxiliary output
(3.3VAUXOA), see Table 2.
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.
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.
Slot A 12V Gate-Drive Output. Connect 12GA to the gate of slot A’s 12V MOSFET. At power-up, V
is raised to the internal charge-pump voltage level by a constant current.
12GA
12GA
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.
8
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.
9
3.3SA-
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, V
3.3GA
10
is charged to 5.5V above the 3.3V supply by a constant current derived from V
.
12VIN
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.
11
FAULTA
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 auto-
restart version, FAULTA is reset when the part initiates the next power-on cycle.
Open-Drain Power-Good Output. PWRGDA goes low t
value and the power MOSFETs are fully enhanced.
after all outputs of slot A reach their final
POR_HL
12
13
PWRGDA
3.3VAUXOA Slot A 3.3V Auxiliary Power-Supply Output
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. V
control logic and analog references of the MAX5946.
is also used to power the internal
14
3.3VAUXIN
3.3VAUXIN
15
16
17
18
3.3VAUXOB Slot B 3.3V Auxiliary Power Output
PWRGDB
FAULTB
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.
12 ______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
Pin Description (continued)
PIN
NAME
FUNCTION
19
3.3SB-
Slot B 3.3V Negative Current-Sense Input. See 3.3SA- function.
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.
20
3.3SB+
21
22
23
24
25
26
27
12GB
12SB-
Slot B 12V Gate-Drive Output. See 12GA function.
Slot B 12V Negative Current-Sense Input. See 12SA- function.
Slot B 12V Positive Current-Sense Input. See 12SA+ function.
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.
12SB+
AUXONB
ONB
FONB
PRES-DETB Slot B Present-Detect Input. See PRES-DETA function.
Overcurrent Timeout Programming Input. Connect a resistor between 500Ω and 500kΩ from TIM to GND
28
TIM
to program t
. Leave TIM floating for a default timeout of 11ms.
FAULT
29
30
31
32
INPUT2
OUTPUT2
OUTPUT1
INPUT1
Digital Logic Gate Input
Digital Output. 4ms debounced digital output of INPUT2.
Digital Output. 4ms debounced digital output of INPUT1.
Digital Logic Gate Input
12V Supply Input. V
drives the gates of the MOSFETs connected to 3.3GA and 3.3GB. 12VIN
12VIN
33
12VIN
powers an internal charge pump that drives the gates of the MOSFETs connected to 12GA and 12GB.
34
35
GND
Ground
PGND
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.
36
PORADJ
At power-up, the MAX5946 keeps all of the external
MOSFETs off until all supplies rise above their respec-
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-man-
agement controller or through an SMBus with an exter-
nal I/O expander. An integrated debounced attention
switch and present-detect signals are included to sim-
plify system design.
tive 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. 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 MAX5946 drives four external n-channel MOSFETs
to control the 12V and 3.3V main outputs. The 3.3V aux-
iliary outputs are controlled through internal 0.24Ω n-
channel 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.
The power requirement for PCI express connectors is
defined by the PCI express card specification and
summarized in Table 1.
______________________________________________________________________________________ 13
Dual PCI Express, Hot-Plug
Controller
R
R
TIM
PORADJ
INPUT1
INPUT2
12VIN
OUTPUT2
OUTPUT1
PWRGDA
FAULTA
TIM
PORADJ
PWRGDB
FAULTB
500mV
12SB+
12SA+
+
-
+
-
+
-
+
-
54mV
R
54mV
500mV
SENSE12A
R
SENSE12B
CHARGE
PUMP
CHARGE
PUMP
12SB-
12GB
12SA-
12GA
5µA
5µA
10µA
10µA
t
FAULT
OSCILLATOR
DEBOUNCE
FAST
OSCILLATOR
t
POR
OSCILLATOR
100mA
0
100mA
150µA
150µA
MAX5946
3.3SA+
3.3SB+
100mV
+
-
+
-
+
+
-
R
20mV
100mV
R
SENSE3.3B
SENSE3.3A
20mV
-
3.3SA-
3.3GA
3.3SB-
3.3GB
5µA
50µA
10µA
BIAS
REFERENCES AND UVLO
10µA
CONTROL LOGIC
CONTROL LOGIC
MAIN-SLOT A
MAIN-SLOT B
150mA
0
150mA
150µA
150µA
3.3VAUXIN
+
-
+
-
VREF
VREF
CHARGE
PUMP
CHARGE
PUMP
CONTROL LOGIC
AUX-SLOT A
CONTROL LOGIC
AUX-SLOT B
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
Table 1. Power Requirements for PCI Express Connectors
POWER RAIL
X1 CONNECTOR
X4/8 CONNECTOR
X16 CONNECTOR
3.3V
Voltage Tolerance
Supply Current
Capacitive Load
12V
9% (max)
3.0A (max)
9% (max)
3.0A (max)
9% (max)
3.0A (max)
1000µF (max)
1000µF (max)
1000µF (max)
Voltage Tolerance
Supply Current
Capacitive Load
3.3V AUXILIARY
Voltage Tolerance
Supply Current
Wake Enabled
375mA (max)
8% (max)
0.5A (max)
300µF (max)
8% (max)
2.1A (max)
8% (max)
5.5A (max)
1000µF (max)
2000µF (max)
9% (max)
375mA (max)
20mA (max)
9% (max)
375mA (max)
20mA (max)
9% (max)
375mA (max)
20mA (max)
Non-Wake Enabled,
Capacitive Load
150µF (max)
150µF (max)
150µF (max)
Table 2. Control Logic Truth Table
3.3VAUXO_
AUXILIARY
OUTPUTS
12V_ AND 3.3V_
ON_
AUXON_
FON_
PRES-DET_
OUTPUTS
X
X
Low
High
High
High
High
High
X
On
Off
Off
On
Off
On
On
Off
Off
Off
On
On
X
X
High
Low*
Low*
Low*
Low*
Low
High
Low
High
Low
Low
High
High
*PRES-DET_ high-to-low transition has a 4ms delay (t
).
DEG
Startup
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 sum-
marizes the logic conditions required for startup.
The main supply outputs can become active only after
all the following events have occurred:
•
•
V
is above its UVLO threshold
3.3VAUXIN
The auxiliary supply input powers the internal control
logic and analog references of the MAX5946, so the
V
and V
are both above their UVLO
12VIN
3.3SA+
threshold
main supplies cannot be enabled if V
present.
is not
3.3VAUXIN
•
•
ON_ is driven high
PRES-DET_ is low for more than 4ms
When an output is enabled, a programmable startup
timer (t ) begins to count the startup time duration.
The auxiliary supply output is made available only after
the following events have occurred:
SU
The value of t
is set to 2x the fault timeout period
SU
(t
). R
externally connected from TIM to GND
FAULT
TIM
•
•
•
V
is above its UVLO threshold
3.3VAUXIN
sets the duration of t
.
FAULT
AUXON_ is driven high
PRES-DET_ is low for more than 4ms
______________________________________________________________________________________ 15
Dual PCI Express, Hot-Plug
Controller
ON_
ON_, AUXON_
V
V
PGTH12
PGTH3.3
V
ON_,TH
12G_, 3.3G_
V
ON_,TH
12G_
V
12ILIM,TH
12VO_, 3.3VO_
3.3VAUXO_
R
SENSE
12V OUTPUT
CURRENT
3.3VAUXO_
PWRGD_
V
PGTH3.3AUX
t
POR_HL
PWRGD_
FAULT_
2 x t
FAULT
3.3VAUXIN
RISING
EDGE
3.3AUXIN
RISING
EDGE
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
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
12G_
V
12ILIM,TH
R
SENSE
12V OUTPUT
CURRENT
then t
. A fault on an auxiliary channel causes all
FAULT
supplies of the affected channel to be disabled after a
PWRGD_
programmable time period t
Management section).
(see the Fault
FAULT
PWRGD_
Power-Good (
Power-good (PWRGD_) is an open-drain output that
pulls low a time (t ) after all of the outputs of the
)
t
FAULT
POR_HL
respective slot are fully on. All outputs are considered
fully on when 3.3G_ has risen to V , 12G_ has
FAULT_
PGTH3.3
PWRGD_ IS PULLED UP TO 3.3VAUXO_.
FAULT_ IS PULLED UP TO 3.3VAUXIN.
risen to V
, and V
is less then
PGTH12
3.3AUXO_
is adjustable from 2.5ms to
A FAULT ON THE 3.3V OUTPUT OR 3.3VAUXO_ OUTPUT PRODUCES SIMILAR RESULTS.
V
. t
PGTH3.3AUX POR_HL
1.5s by connecting a resistor from PORADJ to GND.
Figure 4. 12 Output Overcurrent/Short Circuit During Normal
Operation
See the Setting the Power-On-Reset Timeout Period
(t
) section.
POR
Thermal Shutdown
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
When the die temperature goes above (T ) +150°C, an
SD
overtemperature fault occurs and the MAX5946 shuts
down all outputs. The device waits for the junction temper-
ature to decrease below T - Hysteresis before entering
SD
fault management (see the Fault Management section).
threshold for a period t
, FAULT_ asserts and the
FAULT
16 ______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
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.
FAULT Management
A fault occurs when an overcurrent lasts longer then
FAULT
ature condition.
t
or when the device experiences an overtemper-
•
•
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 logic-low on FON_ forces the respective slot (main
supplies and auxiliary) to turn on regardless of the sta-
tus of the other logic inputs provided the UVLO thresh-
olds are exceeded on all of the inputs.
A fault on the 3.3V auxiliary output shuts down all
three outputs of the respective slot.
The MAX5946A automatically restarts from a fault shut-
down after the t period, while the MAX5946L
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
RESTART
latches off. If an overcurrent fault occurred on a main
output, bring ON_ low for at least t (100µs) and
RESET
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
12V outputs. The current limit is set to 54mV/R
.
SENSE12
R
is either R1 or R3 in the Typical Application
SENSE12
Circuit. Connect a current-sense resistor between
AUXON_ low for a minimum of t
to reset the fault.
3.3S_+ and 3.3S_- to set the current limit for the 3.3V
main outputs to 20mV/R
RESET
Bring ON_ and/or AUXON_ high again to restart the
respective outputs. As an extra protection, the
. R
is either R2
SENSE3.3 SENSE3.3
or R4 in the Typical Application Circuit. For the auxiliary
output (3.3V ) the current limit is fixed at 470mA.
MAX5946L waits a minimum of t
be restarted.
before it can
RESTART
AUXO_
When the voltage across R
or R
SENSE3.3
SENSE12
reaches the current-limit threshold voltage, the
MAX5946 regulates the gate voltage to maintain the
current-limit threshold voltage across the sense resis-
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 tim-
ing diagram describing the INPUT_/OUTPUT_
debounced feature.
tor. If the current limit lasts for t
then an overcur-
FAULT
rent 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 t
, a fault occurs and the
FAULT
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
Present-Detect and Forced-On Inputs
PRES-DET_, FON_
(
)
on if V
, V
, and V
are not present.
3.3VAUXIN
12VIN 3.3VIN
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
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 thresh-
INPUT
old. For either main channel to operate, V
must be above its UVLO threshold.
t
t
t
DBC
3.3VAUXIN
DBC
DBC
DEBOUNCED
OUTPUT
Figure 5. INPUT_ and OUTPUT_ Debounced Feature
______________________________________________________________________________________ 17
Dual PCI Express, Hot-Plug
Controller
SHUT DOWN
12V AND 3.3V OUTPUTS.
ASSERT FAULT_
WAS CURRENT
LIMIT DETECTED ON ANY
12V OR
Y
12V AND 3.3V
OUTPUTS
ARE ENABLED
Y
HAS t
ELAPSED?
FAULT
START COUNTING
t
FAULT
STAY WAITING FOR
3.3V OUTPUT?
t
RESTART
N
N
IS FAULT STILL
PRESENT?
Y
N
RESET t
FAULT
COUNTER
Y
N
LATCH-OFF
OPTION?
RESET FAULT_
AND
RESTART 12V, 3.3V
SUPPLIES
STAY WAITING FOR
ON_ TRANSITION
HIGH->LOW->HIGH
N
POWER-ON MAIN
SUPPLIES FAULT
AND PWRGD ARE
HIGH IMPEDANCE
ENABLE CHARGE ON
12G_ AND 3.3G_
PINS. START
Y
3.3AUXIN IS ON
AND ABOVE UVLO
HAS t
ELAPSED?
SU
COUNTING t
SU
RESET
PWRGD_
POR_LH
ARE PWRGD
THRESHOLDS
REACHED?
N
AFTER t
DELAY
Y
STAY WAITING FOR BOTH
ON_ AND AUXON_
TRANSITION
RESET FAULT_
AND
RESTART ALL SUPPLIES
ASSERT
PWRGD_
AFTER t
DELAY
POR_HL
HIGH->LOW->HIGH
N
Y
POWER-ON AUXILIARY
ENABLE CHARGE ON
Y
SUPPLIES FAULT
AND PWRGD ARE
HIGH IMPEDANCE
INTERNAL AUXILIARY
MOSFET, BEGIN
HAS t ELAPSED?
SU
N
COUNTING t
LATCH-OFF
OPTION?
SU
SHUT DOWN
ALL OUTPUTS,
ASSERT FAULT_,
STAY WAITING FOR
Y
Y
WAS CURRENT LIMIT
DETECTED ON AUXILIARY
OUTPUT?
IS t
ELAPSED?
START COUNTING
FAULT
AUX SUPPLY OUTPUT
IS ENABLED
t
FAULT
t
ELAPSED.
RESTART
N
N
Y
IS FAULT STILL
PRESENT?
N
RESET t
FAULT
COUNTER
Figure 6. Fault Management Flow Chart
18 ______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
External MOSFET Gate Drivers
(12GA, 12GB, 3.3GA, and 3.3GB)
V
× C
LOAD
GATE
t
≥
SU
I
CHG
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
where t = 2 x t
and where
SU
FAULT
1) I
= 5µA.
CHG
V
by an internal charge pump. During turn-on,
12VIN
2) V
= 18.4V for 12G_ and V
= 9.4V for
GATE
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 regu-
lation limits.
GATE
3.3G_.
3) C
is the total capacitance load at the gate.
LOAD
Maximum and minimum values for R
500kΩ, respectively. Leave TIM floating for a default
are 500Ω and
TIM
t
of 11ms.
FAULT
Setting the Power-On-Reset
Timeout Period (t
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 sup-
ply. 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 con-
trol the turn-on time of the external MOSFET. During
turn-off, 3.3G_ sinks 150µA to quickly turn off the exter-
nal MOSFET. During short-circuit events, an internal
150mA current activates to rapidly turn off the appropri-
ate external MOSFET.
)
POR_HL
t
is the time from when the gate voltages of all
POR_HL
outputs of a slot reach their power-good threshold to
when PWRGD_ pulls low. Program the power-on-reset
timeout period (t
RADJ
) by connecting a resistor (R
PO-
POR
) from PORADJ to GND. t
can be calculat-
POR_HL
ed by the following equation:
t
= 2.5µs / Ω x R
POR_HL
PORADJ
Maximum and minimum values for R
are 500Ω
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 con-
nect 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.
PORADJ
and 500kΩ, respectively. Leave PORADJ floating for a
default t of 160ms.
POR
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
R
low enough to have a minimum voltage drop at
DS_ON
full load. High R
causes larger output ripple if
DS_ON
there are pulsed loads. High R
can also trigger
DS_ON
an external undervoltage fault at full load. Determine
the MOSFETs power rating requirement to accommo-
date a short-circuit condition on the board during start-
up. Table 3 lists MOSFETs and sense resistor
manufacturers.
Applications Information
Setting the Fault Timeout Period (t
)
FAULT
t
is the time an overcurrent or overtemperature
FAULT
fault must remain for the MAX5946 to disable the main
or auxiliary channels of a particular slot. Program the
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.
fault timeout period (t
TIM
the following equation:
) by connecting a resistor
FAULT
FAULT
(R ) from TIM to GND. t
can be calculated by
Maximum Load Capacitance
Large capacitive loads at the 12V output, the 3.3V out-
put, and the 3.3V auxiliary output can cause a problem
when inserting discharged PCI cards into live back-
planes. A fault occurs if the time needed to charge the
capacitance of the board is greater than the typical
t
= 166ns / Ω x R
TIM
FAULT
The t
programmed time duration must be chosen
FAULT
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:
startup time (2 x t
). The MAX5946 can withstand
FAULT
______________________________________________________________________________________ 19
Dual PCI Express, Hot-Plug
Controller
Table 3. Component Manufacturers
COMPONENT
MANUFACTURER
Vishay-Dale
IRC
PHONE
402-564-3131
704-264-8861
888-522-5372
310-322-3331
602-244-3576
—
WEBSITE
www.vishay.com
Sense Resistor
www.irctt.com
Fairchild
www.fairchildsemi.com
www.irf.com
International Rectifier
Motorola
MOSFETs
www.mot-sps.com/ppd/
www.vishay.com
Vishay-Siliconix
large capacitive loads due to their adjustable startup
times and adjustable current-limit thresholds. Calculate
the maximum load capacitance as follows:
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.
t
× I
SU LIM
V
C
<
LOAD
Chip Information
TRANSISTOR COUNT: 10,487
OUT
V
is either the 3.3V output, the 12V output, or the
OUT
PROCESS: BiCMOS
3.3V auxiliary output for slot A or slot B.
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
Typical Application Circuit
V
12VIN
PCI EXPRESS
SLOT A
PCI EXPRESS
SLOT B
ADD-IN
CARD
IN5819
Q1
Q3
PRSNT1
+12V
V
PRSNT1
+12V
3.3AUXIN
R1
8mΩ
R3
8mΩ
SI7448DP-T1
SI7448DP-T1
1µF
0.1µF
GND
GND
PWRGD
PWRGD
PWRGDA
PWRGDB
10kΩ
10kΩ
MAX5946
3.3VAUX
3.3VAUX
3.3VAUXOA
GND
3.3VAUXOB
PORADJ
R
= OPEN
PORADJ
R
=
TM
OPEN
2
2
R2
5mΩ
R4
5mΩ
Q2
Q4
SI7448DP-T1
SI7448DP-T1
+3.3V
+3.3V
3.3V INPUT
0.1µF
2
2
2
2
V
3.3AUXIN
PRSNT2
PRSNT2
10kΩ
MAX7313ATG
16-BIT I/O EXPANDER
MRL
MRL
LED's
LED's
2
2
2
3
SMBus
AO-2
INT
______________________________________________________________________________________ 21
Dual PCI Express, Hot-Plug
Controller
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.)
22 ______________________________________________________________________________________
Dual PCI Express, Hot-Plug
Controller
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.)
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.
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