MAXIM MAX5954AETX+

19-3914; Rev 1; 1/06
KIT
ATION
EVALU
LE
B
A
IL
A
AV
Single PCI Express, Hot-Plug
Controller
♦ PCI Express Compliant
♦ Hot Swaps 12V, 3.3V, and 3.3V Auxiliary for a
Single PCI-E Slot
♦ Integrated Power MOSFET for Auxiliary Supply
Rail
♦ Controls dI/dt and dV/dt
♦ Active Current Limiting Protects Against
Overcurrent/Short-Circuit Conditions
♦ Programmable Current-Limit Timeout
♦ PWRGD Signal Output with Programmable
Power-On Reset (POR) (160ms Default)
♦ Latched FAULT Signal Output after Overcurrent
or Overtemperature Fault
♦ Attention Switch Input/Output with 4.4ms
Debounce
♦ Present-Detect Input
♦ Forced-On Input Facilitates Testing
♦ Thermal Shutdown
♦ Allows Control through SMBus with an I/O
Expander
Ordering Information
PINPACKAGE
PKG
CODE
MAX5954AETX+ -40°C to +85°C
36 Thin QFN
T3666-3
MAX5954LETX+ -40°C to +85°C
36 Thin QFN
T3666-3
PART
TEMP RANGE
+Denotes lead free package.
N.C.
N.C.
N.C.
TOP VIEW
T2
T1
N.C.
N.C.
Pin Configuration
N.C.
N.C.
The MAX5954 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 a single PCI Express (PCI-E) slot. The MAX5954’s logic
inputs/outputs allow interfacing directly with the system
hot-plug management controller or through an SMBus™
with an external I/O expander. Integrated debounced
attention switch and present-detect signals are included
to simplify system design.
The MAX5954 drives two external n-channel MOSFETs
to control the 12V and 3.3V main outputs. The 3.3V auxiliary output is controlled through an internal 0.3Ω
n-channel MOSFET. An internal charge pump provides
gate drive for the 12V output while the gate drive of the
3.3V output is driven by the 12V input supply. The 3.3V
auxiliary output is completely independent from the
main outputs with its own charge pump.
At power-up, the MAX5954 keeps all of the external
MOSFETs off until the supplies rise above their respective undervoltage-lockout (UVLO) thresholds. The
device keeps the internal MOSFET off only until the auxiliary input supply rises above its UVLO threshold. Upon
a turn-on command, the MAX5954 enhances the external and internal MOSFETs slowly with a constant gate
current to limit the power-supply inrush current. The
MAX5954 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
MAX5954L latches off while the MAX5954A 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
27 26 25 24 23 22 21 20 19
Applications
TIM 28
N.C. 29
Embedded Devices
N.C.
OUTPUT
INPUT
12VIN
30
16
31
15
33
13
GND
PGND
PORADJ
34
12
35
11
32
10
36
+
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.
14
MAX5954
1
2
3
4
5
6
7
8
N.C.
N.C.
N.C.
N.C.
3.3VAUXIN
3.3VAUXO
PWRGD
FAULT
3.3G
9
12S12G
3.3S+
3.3S-
Workstations
17
ON
AUXON
12S+
Desktop Mobile Server Platforms
18
PRES-DET
FON
Servers
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
MAX5954
General Description
MAX5954
Single PCI Express, Hot-Plug
Controller
ABSOLUTE MAXIMUM RATINGS
(All voltages referenced to GND, unless otherwise noted.)
12VIN......................................................................-0.3V to +14V
12G............................................................-0.3V to (V12VIN + 6V)
12S, 12S-, 3.3G ......................................-0.3V to (V12VIN + 0.3V)
3.3VAUXIN, ON, FAULT ..........................................-0.3V to +6V
PWRGD ....................................................................-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
54
59
mV
12VIN CONTROL
12VIN Current-Limit
Threshold (V12S+ - V12S-)
V12ILIM
12G Gate Charge Current
I12G_CHG
12G Gate Discharge Current
12G Gate High Voltage
(V12G - V12VIN)
12G Threshold Voltage For
PWRGD Assertion
I12G_DIS
V12GH
VPGTH12
49
V12G = GND
4
5
6
µA
Normal turn-off, ON = GND, V12G = 2V
50
150
250
µA
Output short-circuit condition, strong gate pulldown
to regulation, V12VIN - V12S_ ≥ 1V, V12G_= 5V
50
120
180
mA
I12G = 1µA
4.8
5.3
5.8
V
Referred to V12VIN, I12G_ = 1µA (Note 2)
3.0
4
4.8
V
1
µA
20
60
µA
12S- Input Bias Current
12S+ Input Bias Current
3.3V SUPPLY
3.3V Supply Voltage Range
Undervoltage Lockout
(Note 3)
2
V3.3S+
3.3S+ rising
Hysteresis
3.0
3.3
3.6
V
2.52
2.65
2.78
V
30
_______________________________________________________________________________________
mV
Single 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-)
3.3G Gate Charge Current
V3.3ILIM
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 (Note 2)
-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
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)
376
470
VPGTH3.3AUX (Note 3)
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
Hysteresis
25
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
MAX5954
ELECTRICAL CHARACTERISTICS (continued)
MAX5954
Single 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 Output-High
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
Fault Reset Minimum Pulse
Width
Thermal-Shutdown Threshold
tRESET
(Note 4)
100
µs
TSD
TJ rising
+150
°C
20
°C
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 3.3S+.
This is the time that ON or AUXON must stay low when resetting a fault condition.
_______________________________________________________________________________________
0.4
ms
V
V
Single PCI Express, Hot-Plug
Controller
(V12VIN = V12S+ = 12V, V3.3VAUXIN = V3.3S+ = VON = VAUXON = VINPUT = 3.3V, PRES-DET = GND, FON = PORADJ = TIM = float,
FAULT = 10kΩ to 3.3VAUXIN, PWRGD = 10kΩ to 3.3VAUXO, TA = +25°C, unless otherwise noted, see the Typical Application
Circuit.)
3.3VAUXIN SUPPLY CURRENT
vs. TEMPERATURE
1.9
THRESHOLD VOLTAGE (V)
1.6
1.4
1.2
1.0
0.8
0.6
10
35
60
1.8
1.7
1.6
1.5
1.4
1.3
0.4
1.2
0.2
1.1
1.0
-40
85
MAX5954 toc03
2.0
MAX5954 toc02
1.8
SUPPLY CURRENT (mA)
-15
-15
10
35
60
85
-40
-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
MAX5954 toc06
5.30
GATE DISCHARGE CURRENT (µA)
3.0
5.35
MAX5954 toc05
MAX5954 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
0
12V CURRENT-SENSE
THRESHOLD
40
3.3V CURRENT-SENSE
THRESHOLD
30
20
10
-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
-40
85
MAX5954 toc09
50
0.500
AUXILIARY CURRENT LIMIT (A)
0.14
MAX5954 toc08
0.16
60
CURRENT-LIMIT THRESHOLD VOLTAGE (mV)
AUXILIARY OUTPUT CURRENT = 375mA
0.18
MAX5954 toc07
OUTPUT CURRENT (A)
0.20
DROPOUT VOLTAGE (V)
ON AND AUXON LOW-TO-HIGH THRESHOLD
VOLTAGE vs. TEMPERATURE
0
-40
OUTPUT VOLTAGE (V)
2.0
MAX5954 toc01
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
GATE CHARGE CURRENT (µA)
SUPPLY CURRENT (mA)
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
MAX5954
Typical Operating Characteristics
Typical Operating Characteristics (continued)
(V12VIN = V12S+ = 12V, V3.3VAUXIN = V3.3S+ = VON = VAUXON = VINPUT = 3.3V, PRES-DET = GND, FON = PORADJ = TIM = float,
FAULT = 10kΩ to 3.3VAUXIN, PWRGD = 10kΩ to 3.3VAUXO, TA = +25°C, unless otherwise noted, see the Typical Application
Circuit.)
3.3VAUXIN UNDERVOLTAGE-LOCKOUT
THRESHOLD vs. TEMPERATURE
12VIN UNDERVOLTAGE-LOCKOUT
THRESHOLD vs. TEMPERATURE
10.15
MAX5954 toc11
2.70
MAX5954 toc10
10.20
2.68
10.10
UVLO THRESHOLD (V)
UVLO THRESHOLD (V)
MAX5954
Single PCI Express, Hot-Plug
Controller
10.05
10.00
9.95
9.90
2.66
2.64
2.62
9.85
2.60
9.80
-40
-15
10
35
60
-40
85
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
12V TURN-ON/OFF TIME
3.3V TURN-ON/OFF TIME
MAX5954 toc12
MAX5954 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
MAX5954 toc15
MAX5954 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
_______________________________________________________________________________________
Single 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
MAX5954 toc17
MAX5954 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 VOLTAGE
3.3VAUXO
5V/div
5V/div
PWRGD
3.3G
10V/div
PWRGD
5V/div
4ms/div
100ms/div
FAULT CONDITION ON 12V OUTPUT
(AUTORESTART OPTION MAX5954A)
FAULT CONDITION ON 3.3V OUTPUT
(AUTORESTART OPTION MAX5954A)
MAX5954 toc18
RLOAD STEP TO 1.5Ω
MAX5954 toc19
12V OUTPUT CURRENT
5A/div
RLOAD STEP TO 0.5Ω
12G
20V/div
3.3G
10V/div
12V OUTPUT VOLTAGE
10V/div
tRESTART
FAULT
5V/div
100ms/div
3.3V OUTPUT VOLTAGE
5V/div
tRESTART
FAULT
5V/div
100ms/div
FAULT CONDITION ON 12V OUTPUT
(LATCH OPTION MAX5954L)
FAULT CONDITION ON AUXILIARY OUTPUT
(AUTORESTART OPTION MAX5954A)
MAX5954 toc21
MAX5954 toc20
RLOAD STEP TO 4Ω
3.3V MAIN OUTPUT CURRENT
2A/div
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
MAX5954
Typical Operating Characteristics (continued)
(V12VIN = V12S+ = 12V, V3.3VAUXIN = V3.3S+ = VON = VAUXON = VINPUT = 3.3V, PRES-DET = GND, FON = PORADJ = TIM = float,
FAULT = 10kΩ to 3.3VAUXIN, PWRGD = 10kΩ to 3.3VAUXO, TA = +25°C, unless otherwise noted, see the Typical Application
Circuit.)
MAX5954
Single PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V12VIN = V12S+ = 12V, V3.3VAUXIN = V3.3S+ = VON = VAUXON = VINPUT = 3.3V, PRES-DET = GND, FON = PORADJ = TIM = float,
FAULT = 10kΩ to 3.3VAUXIN, PWRGD = 10kΩ to 3.3VAUXO, TA = +25°C, unless otherwise noted, see the Typical Application
Circuit.)
FAULT CONDITION ON 3.3V OUTPUT
(LATCH OPTION MAX5954)
FAULT CONDITION ON 12V OUTPUT
MAX5954 toc22
tFAULT
RLOAD
STEP TO 1.5Ω
MAX5954 toc23
12V OUTPUT CURRENT
5A/div
RLOAD STEP TO 0.5Ω
3.3V OUTPUT CURRENT
2A/div
12G
20V/div
3.3G
10V/div
12V OUTPUT VOLTAGE
10V/div
3.3V OUTPUT VOLTAGE
5V/div
FAULT
5V/div
4ms/div
100ms/div
FAULT CONDITION ON AUXILIARY OUTPUT
(LATCH OPTION MAX5954)
FAULT CONDITION ON 3.3V MAIN OUTPUT
MAX5954 toc24
tFAULT
FAULT
5V/div
RLOAD
STEP TO 0.5Ω
MAX5954 toc25
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
4ms/div
100ms/div
SHORT CIRCUIT ON 12V OUTPUT
FAULT CONDITION ON AUXILIARY OUTPUT
MAX5954 toc27
MAX5954 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
_______________________________________________________________________________________
Single PCI Express, Hot-Plug
Controller
SHORT CIRCUIT ON 12V OUTPUT
SHORT CIRCUIT ON 3.3V OUTPUT
MAX5954 toc28
MAX5954 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
MAX5954 toc31
MAX5954 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_
MAX5954 toc32
MAX5954 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
MAX5954
Typical Operating Characteristics (continued)
(V12VIN = V12S+ = 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.)
MAX5954
Single PCI Express, Hot-Plug
Controller
Typical Operating Characteristics (continued)
(V12VIN = V12S+ = 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)
MAX5954 toc34
MAX5954 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
MAX5954 toc36
MAX5954 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
4ms/div
40ms/div
FORCED-ON (ON/OFF) OPERATION
FORCED-ON (ON/OFF) OPERATION
MAX5954 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
MAX5954 toc39
4ms/div
______________________________________________________________________________________
Single PCI Express, Hot-Plug
Controller
POWER-ON RESET TIME
vs. PORADJ RESISTOR
DEBOUNCED ON/OFF OPERATION
MAX5954 toc40
MAX5954 toc41
1600
1400
INPUT
2V/div
tPOR_HL (MS)
1200
OUTPUT
2V/div
1000
800
600
400
200
0
0
10ms/div
50 100 150 200 250 300 350 400 450 500
RPORADJ (KΩ)
tFAULT TIME DELAY
vs. TIM RESISTOR
MAX5954 toc42
120
tFAULT (ms)
100
80
60
40
20
0
0
50 100 150 200 250 300 350 400 450 500
RTIM (kΩ)
______________________________________________________________________________________
11
MAX5954
Typical Operating Characteristics (continued)
(V12VIN = V12S+ = 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.)
Single PCI Express, Hot-Plug
Controller
MAX5954
Pin Description
PIN
NAME
FUNCTION
1
PRES-DET
Present-Detect Input. PRES-DET accepts inputs from the PRSNT#2 pin on a PCI-E connector. PRES-DET
has an internal pullup to 3.3VAUXIN. When PRES-DET is low, the outputs follow the command from ON
and AUXON after a 4ms debounced time. When PRES-DET goes from low to high, all outputs of the
respective slot shut down with no delay (see Table 2).
2
FON
Forced-On Input. FON has a 50kΩ internal pullup to 3.3VAUXIN. A logic-low on FON turns on all PCI-E
outputs as long as the power inputs are within their operating range, regardless of the status of the other
input signals. Leave FON open for normal operation (see Table 2).
3
ON
4
AUXON
5
12S+
12V Positive Current-Sense Input. Connect the positive terminal of the current-sense resistor to 12S+
using the Kelvin-sensing technique to assure accurate current sensing.
6
12S-
12V Negative Current-Sense Input. Connect 12S- to the negative side of the current-sense resistor using
the Kelvin-sensing technique to assure accurate current sensing.
7
12G
12V Gate-Drive Output. Connect 12G to the gate of the 12V MOSFET. At power-up, V12G
is raised to the internal charge-pump voltage level by a constant current.
8
3.3S+
3.3V Positive Current-Sense Input. Connect the positive side of the current-sense resistor to 3.3S+ using
the Kelvin-sensing technique to assure accurate current sensing. This input is also used for the 3.3V
supply’s UVLO function.
9
3.3S-
3.3V Negative Current-Sense Input. Connect to the negative side of the sense resistor using the Kelvinsensing technique to assure accurate current sensing.
10
3.3G
3.3V Gate-Drive Output. Connect 3.3G to the gate of the 3.3V MOSFET. At power-up, V3.3G
is charged to 5.5V above the 3.3V supply by a constant current derived from V12VIN.
12V and 3.3V Outputs Enable. A logic-high at ON turns on the 12V and 3.3V outputs (see Table 2).
3.3V Auxiliary Output Enable. A logic-high at AUXON turns on the auxiliary output (3.3VAUXO) (see Table 2).
Open-Drain Fault Output Signal. FAULT latches active low whenever the 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, FAULT must be reset by toggling the ON input. If the fault is in
the auxiliary output, FAULT must be reset by toggling both ON and AUXON. For the auto-restart version,
FAULT is reset when the part initiates the next power-on cycle.
11
FAULT
12
PWRGD
13
3.3VAUXO
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 MOSFET
connecting 3.3VAUXIN to 3.3VAUXO. V3.3VAUXIN is also used to power the internal control logic and
analog references of the MAX5954.
15–23,
26, 27,
29, 30
N.C.
24
T1
12
Open-Drain Power-Good Output. PWRGD goes low tPOR_HL after all outputs reach their final value and
the power MOSFETs are fully enhanced.
No Connection. Not internally connected.
Test Input. Connect T1 to GND.
______________________________________________________________________________________
Single PCI Express, Hot-Plug
Controller
PIN
NAME
25
T2
Test Input. Connect T2 to GND.
FUNCTION
28
TIM
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.
31
OUTPUT
32
INPUT
Digital Logic Gate Input
33
12VIN
12V Supply Input. V12VIN drives the gate of the MOSFET connected to 3.3G. 12VIN powers an internal
charge pump that drives the gate of the MOSFET connected to 12G.
34
GND
Ground
35
PGND
36
PORADJ
Digital Output. 4ms debounced digital output of 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 MAX5954 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 a
single PCI Express slot. The MAX5954’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 MAX5954 drives two external n-channel MOSFETs
to control the 12V and 3.3V main outputs. The 3.3V auxiliary output is controlled through an internal 0.3Ω
n-channel MOSFET. An internal charge pumps provides a gate drive for the 12V output while the gate
drive of the 3.3V output is driven by the 12V input supply. The 3.3V auxiliary output is completely independent from the main outputs with its own charge pump.
At power-up, the MAX5954 keeps all of the external
MOSFETs off until all supplies rise above their respective UVLO thresholds. The device keeps the internal
MOSFET off only until the 3.3VAUXIN supply rises
above its UVLO threshold. Upon a turn-on command,
the MAX5954 enhances the external and internal
MOSFETs slowly with a constant gate current to limit
the power-supply inrush current. The MAX5954 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 MAX5954L latches
off while the MAX5954A 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.
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 3.3S+ are both above their UVLO
threshold
•
ON is driven high
•
PRES-DET is low for more than 5ms
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 5ms
The FON input overrides all other control signals and
turns on the PCI Express 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 MAX5954, 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
______________________________________________________________________________________
13
MAX5954
Pin Description (continued)
MAX5954
Single PCI Express, Hot-Plug
Controller
RTIM
RPORADJ
IN
OUT
12VIN
PWRGD
FAULT
PORADJ
TIM
12S+
+
-
108mV
+
-
54mV
RSENSE12
12S-
CHARGE
PUMP
5µA
12G
Aµ01
10µA
tFAULT
OSCILLATOR
DEBOUNCE
tPOR
OSCILLATOR
FAST
OSCILLATOR
Aµ001
100mA
150µA
40mV
+
-
3.3S+
+
-
RSENSE3.3
20mV
3.3S5µA
3.3G
Aµ01
10µA
BIAS, REFERENCES
AND UVLO
CONTROL LOGIC
MAIN-CHANNEL
Aµ051
150mA
150µA
3.3V
VREF +
-
MAX5954
CHARGE
PUMP
CONTROL LOGIC
AUX-CHANNEL
UVLO
3.3AUXO
INPUT COMPARATORS AND CHIP CONTROL LOGIC
ON
AUXON
FON
PRES-DET
PGND
GND
Figure 1. Functional Diagram
14
______________________________________________________________________________________
AUXIN
Single PCI Express, Hot-Plug
Controller
MAX5954
Table 1. Power Requirements for PCI Express Connectors
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)
±9% (max)
±9% (max)
±9% (max)
Supply Current, Wake Enabled
375mA (max)
375mA (max)
375mA (max)
Supply Current, Non-Wake Enabled
20mA (max)
20mA (max)
20mA (max)
Capacitive Load
150µF (max)
150µF (max)
150µF (max)
3.3V
Capacitive Load
12V
Capacitive Load
3.3V AUXILIARY
Voltage Tolerance
Table 2. Control Logic Truth Table
ON
AUXON
X
X
X
X
PRES-DET
12V AND 3.3V
OUTPUTS
3.3VAUXO
AUXILIARY
OUTPUT
Low
X
On
On
High
High
Off
Off
Off
FON
Low
Low
High
Low*
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 5ms delay (tDEG).
(tFAULT). RTIM externally connected from TIM to GND
sets the duration of tFAULT.
12V and 3.3V Outputs Normal Operation
The MAX5954 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
controller disengages both the 12V and 3.3V outputs
(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 than tFAULT. A fault on an auxiliary channel
causes all supplies to be disabled after a programmable
time period tFAULT (see the Fault Management section).
Power-Good (PWRGD)
Power-good (PWRGD) is an open-drain output that
pulls low a time (tPOR_HL) after all of the outputs are
fully on. All outputs are considered fully on when 3.3G
has risen to VPGTH3.3, 12G has risen to VPGTH12, and
V 3.3AUXO is less than 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-OnReset Timeout Period (tPOR) section.
______________________________________________________________________________________
15
MAX5954
Single 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
3.3VAUXIN
RISING
EDGE
FAULT
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)
Fault Management
12G
V12ILIM,TH
RSENSE
12V OUTPUT
CURRENT
•
PWRGD
The MAX5954A automatically restarts from a fault shutdown after the tRESTART period, while the MAX5954L
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
MAX5954L waits a minimum of tRESTART before it can
be restarted.
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. 12V Output Overcurrent/Short Circuit During Normal
Operation
Thermal Shutdown
When the die temperature goes above +150°C (TSD), an
overtemperature fault occurs and the MAX5954 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).
16
A fault occurs when an overcurrent lasts longer then
tFAULT or when the device experiences an overtemperature condition.
• A fault on a main output (12V or 3.3V) shuts down
both main outputs. The 3.3V auxiliary is not affected.
A fault on the 3.3V auxiliary output shuts down all
three outputs.
Debounced Logic Gate
(Input and Output)
INPUT accepts an input from a mechanical switch. The
corresponding output (OUTPUT) is debounced for
4.4ms. When INPUT goes from high to low, OUTPUT
goes low right away and stays low for at least 4.4ms.
After the debounce time OUTPUT follows INPUT. If INPUT
goes from low to high, OUTPUT goes high right away and
______________________________________________________________________________________
Single PCI Express, Hot-Plug
Controller
Present-Detect and Forced-On Inputs
(PRES-DET, FON)
PRES-DET input detects 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 output after a 4ms debounced time. When the card is
removed, an internal 50kΩ pullup forces PRES-DET
high and the PCI Express slot is shut down with no
delay. PRES-DET works in conjunction with ON and
AUXON and only enables the device when ON and
AUXON are high.
A logic-low on FON forces the PCI Express 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.
Connect a current-sense resistor between 12S+ and
12S- to set the current limit for the 12V output. The current limit is set to 54mV/R SENSE12 . Connect a
current-sense resistor between 3.3S+ and 3.3S- to
set the current limit for the 3.3V main output to
20mV/RSENSE3.3. 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
MAX5954 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 MAX5954 shuts down both the
12V and 3.3V outputs and asserts the FAULT output.
When the auxiliary output reaches the current limit
(470mA) for longer than tFAULT, a fault occurs and the
device shuts down all outputs and asserts FAULT.
INPUT
tDBC
tDBC
tDBC
DEBOUNCED
OUTPUT
Undervoltage-Lockout Threshold
The UVLO thresholds prevent the internal auxiliary
MOSFET and the external main channel MOSFETs (Q1
and Q2 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 (12G
and 3.3G) 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 3.3S+ and has a UVLO threshold of
2.65V. The auxiliary supply is monitored at 3.3VAUXIN
and has a 2.65V UVLO threshold. For the main outputs to
operate, V3.3VAUXIN must be above its UVLO threshold.
External MOSFET Gate Driver
(12G and 3.3G)
The gate drive for the external MOSFETs is provided at
12G and 3.3G. 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 120mA 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 external
MOSFET.
Auxiliary Supply (3.3VAUXIN)
3.3VAUXIN provides power to the auxiliary output as
well as the internal logic and references. The drain of the
internal auxiliary MOSFET connects to 3.3VAUXIN
through internal sense resistor and the source connects
to the auxiliary output 3.3VAUXO. The MOSFET’s typical
on-resistance is 0.3Ω. An internal charge pump boosts
the gate-drive voltage to fully turn on the internal n-channel MOSFET. The auxiliary supply has an internal current
limit set to 470mA.
Figure 5. INPUT and OUTPUT Debounced Feature
______________________________________________________________________________________
17
MAX5954
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.
MAX5954
Single 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
______________________________________________________________________________________
Single PCI Express, Hot-Plug
Controller
Setting the Fault Timeout Period (tFAULT)
tFAULT is the time an overcurrent or overtemperature
fault must remain for the MAX5954 to disable the main
or auxiliary outputs. 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
12G and 3.3G. To properly power-up the main supply
outputs, the following constraints need to be taken:
V
× CLOAD
t SU ≥ GATE
ICHG
Maximum and minimum values for RPORADJ are 500kΩ
and 500Ω, 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
MOSFET’s 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 Capacitance
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.
where tSU = 2 x tFAULT and where:
1) ICHG = 5µA.
2) VGATE = 18.4V for 12G and VGATE = 9.4V for 3.3G.
3) CLOAD is the total capacitance load at the gate.
Maximum and minimum values for RTIM are 500kΩ and
500Ω, 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 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:
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 MAX5954 can withstand
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.
tPOR_HL = 2.5µs / Ω x RPORADJ
Table 3. Component Manufacturers
COMPONENT
Sense Resistor
MOSFETs
MANUFACTURER
PHONE
WEBSITE
Vishay-Dale
402-564-3131
www.vishay.com
IRC
704-264-8861
www.irctt.com
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
—
www.vishay.com
______________________________________________________________________________________
19
MAX5954
Applications Information
MAX5954
Single PCI Express, Hot-Plug
Controller
Chip Information
Input Transients
The 12V input (12VIN), the 3.3V input (3.3S+), and the
3.3V auxiliary (3.3VAUXIN) must be above their UVLO
thresholds before startup can occur. Input transients
can cause the input voltage to sag below the UVLO
threshold. The MAX5454 rejects transients on the input
supplies that are shorter than 4µs (typ).
20
PROCESS: BiCMOS
______________________________________________________________________________________
Single PCI Express, Hot-Plug
Controller
V12VIN
ADD-IN
CARD
PCI EXPRESS
SLOT
1µF
Q1
SI7448DP-T1
PRSNT1#
IN5819
V3.3AUXIN
R1
8mΩ
+12V
12VIN
3.3AUXIN
12S-
12G
GND
12S+
0.1µF
PWRGD
PWRGD#
RTIM = OPEN
10kΩ
3.3VAUX
TIM
MAX5954
3.3VAUX0
RPORADJ = OPEN
PGND
PORADJ
Q2
SI7448DP-T1
OUTPUT
INPUT
ON
AUXON
FON
FAULT
PRES-DET
3.3S+
3.3S-
3.3G
GND
R2
5mΩ
V3.3VIN
ATTENTION
SWITCH
+3.3V
V3.3AUXIN
0.1µF
10kΩ
PRSNT2#
MRL
MAX7311
16-BIT I/O EXPANDER
LEDs
2
2
3
SMBUS
AO-2
INT
______________________________________________________________________________________
21
MAX5954
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.)
QFN THIN.EPS
MAX5954
Single PCI Express, Hot-Plug
Controller
(NE-1) X e
E
E/2
k
D/2
CL
(ND-1) X e
D
D2
D2/2
e
b
E2/2
L
CL
k
E2
e
L
CL
CL
L1
L
L
e
A1
A2
e
A
PACKAGE OUTLINE
36, 40, 48L THIN QFN, 6x6x0.8mm
21-0141
F
1
2
NOTES:
1. DIMENSIONING & TOLERANCING CONFORM TO ASME Y14.5M-1994.
2. ALL DIMENSIONS ARE IN MILLIMETERS. ANGLES ARE IN DEGREES.
3. N IS THE TOTAL NUMBER OF TERMINALS.
4. THE TERMINAL #1 IDENTIFIER AND TERMINAL NUMBERING CONVENTION SHALL CONFORM TO JESD 95-1
SPP-012. DETAILS OF TERMINAL #1 IDENTIFIER ARE OPTIONAL, BUT MUST BE LOCATED WITHIN THE
ZONE INDICATED. THE TERMINAL #1 IDENTIFIER MAY BE EITHER A MOLD OR MARKED FEATURE.
5. DIMENSION b APPLIES TO METALLIZED TERMINAL AND IS MEASURED BETWEEN 0.25 mm AND 0.30 mm
FROM TERMINAL TIP.
6. ND AND NE REFER TO THE NUMBER OF TERMINALS ON EACH D AND E SIDE RESPECTIVELY.
7. DEPOPULATION IS POSSIBLE IN A SYMMETRICAL FASHION.
8. COPLANARITY APPLIES TO THE EXPOSED HEAT SINK SLUG AS WELL AS THE TERMINALS.
9. DRAWING CONFORMS TO JEDEC MO220, EXCEPT FOR 0.4mm LEAD PITCH PACKAGE T4866-1.
10. WARPAGE SHALL NOT EXCEED 0.10 mm.
11. MARKING IS FOR PACKAGE ORIENTATION REFERENCE ONLY.
12. NUMBER OF LEADS SHOWN FOR REFERENCE ONLY.
PACKAGE OUTLINE
36, 40, 48L THIN QFN, 6x6x0.8mm
21-0141
F
2
2
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
Printed USA
is a registered trademark of Maxim Integrated Products, Inc.