MAX5915AEUI+T中文资料

General Description

The MAX5915/MAX5915A/MAX5916/MAX5916A dual PCI 2.2 hot-swap controllers allow for safe insertion and removal of two PCI cards into live PCI slots or back-planes by limiting the inrush current at startup. After startup, these devices provide protection against short-circuit, overcurrent, and undervoltage conditions.

The MAX5915/MAX5915A/MAX5916/MAX5916A pro-vide independent power controls for +3.3V, +5V, ±12V,and +3.3V auxiliary supplies of two PCI cards. These devices provide intelligent selective thermal shutdown control that shuts down the channel with an overcurrent fault. All devices include internal power MOSFETs for the +12V, -12V, and +3.3V auxiliary outputs. These devices use internal charge pumps to activate the gates of the internal FETs controlling the +3.3V auxiliary supply.Internal FETs and current-sense circuitry regulate the ±12V and the +3.3V auxiliary supplies. Channels A and B operate independently, allowing a single device to moni-tor two PCI card slots.

The MAX5915/MAX5915A offer latched fault protection and the MAX5916/MAX5916A offer autorestart fault pro-tection. The devices are available in the low-profile 28-pin TSSOP package.

Features

?PCI 2.2 Compliant

?Independent Power Controls for +3.3V, +5V, ±12V,and +3.3V Auxiliary Supplies of Two PCI Cards ?Internal MOSFET Switches for ±12V and +3.3V Auxiliary Outputs ?Separate ON/OFF Control Input for Each Channel ?Independent +3.3V Auxiliary Output ON/OFF Control ?Overcurrent Foldback with Timeout and Shutdown Protection for ±12V and +3.3V Auxiliary Rails with Status Report ?Brick Wall with Timeout and Shutdown Protection for +5V and +3.3V Rails with Status Report ?Output Undervoltage Monitoring for +3.3V, +5V,+12V, and +3.3V Auxiliary Rails with Status Report ?+3.3V Auxiliary Autorestart

?Intelligent Selective Thermal Shutdown Control Shuts Down Only the Channel with an Overcurrent Fault ?28-Pin TSSOP Package

MAX5915/MAX5915A/MAX5916/MAX5916A

Dual PCI 2.2 Hot-Swap Controllers

________________________________________________________________Maxim Integrated Products 1

19-2420; Rev 2; 9/05

For pricing, delivery, and ordering information,please contact Maxim/Dallas Direct!at 1-888-629-4642, or visit Maxim’s website at https://www.sodocs.net/doc/0f4957247.html,.

Ordering Information

Applications

PCI 2.2 Server PCI Server RAID

Selector Guide, Pin Configuration, Functional Diagram, and Typical Operating Circuit appear at end of data sheet.

Typical Application Circuit

*Contact factory for availabilty.

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Dual PCI 2.2 Hot-Swap Controllers 2_______________________________________________________________________________________

ABSOLUTE MAXIMUM RATINGS

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.

+12VIN to GND ...................................................-0.3V to +14.0V -12VIN to GND........................................................-14V to +0.3V -12VO_ to GND......................................+0.3V to (V -12VIN - 0.3V)+12VO_, 3.3VGATE_, 5VGATE_

to GND..................................................-0.3V to (V +12VIN + 0.3V)Any Other Pin to GND ...........................................-0.3V to +6.0V Continuous Power Dissipation (T A = +70°C)

28-Pin TSSOP (derate 23.8mW/°C above +70°C)...........1.9W

Operating Temperature Ranges:

MAX591_U_ _......................................................0°C to +85°C MAX591_A U_ _...................................................0°C to +85°C MAX591_E_ _....................................................-40°C to +85°C MAX591_ AE_ _................................................-40°C to +85°C Maximum Junction Temperature.....................................+150°C Storage Temperature Range.............................-65°C to +150°C Lead Temperature (soldering, 10s).................................+300°C

ELECTRICAL CHARACTERISTICS

ELECTRICAL CHARACTERISTICS (continued)

MAX5915/MAX5915A/MAX5916/MAX5916A Dual PCI 2.2 Hot-Swap Controllers

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Dual PCI 2.2 Hot-Swap Controllers 4_______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

Note 3:t DEG is negative edge triggered. ON_ or AUXON_ transition from low to high has no delay.Note 4:Temperature threshold at which the outputs of the channel with overcurrent shut down.Note 5:The temperature threshold at which both channels shut down.

MAX5915/MAX5915A/MAX5916/MAX5916A

Dual PCI 2.2 Hot-Swap Controllers

_______________________________________________________________________________________5

Typical Operating Characteristics

(V +12VIN = +12V, V 3.3VAUXIN = +3.3V, V -12VIN = -12V, V 5V = +5V, V 3.3V = +3.3V, R 5VSEN_= 0.005?, R 3.3VSEN_ = 0.005?, C 3.3VO_ =

M A X 5915 t o c 09

OUTPUT CURRENT (A)

3.3V A U X _ V O L T A G E (V )

1.05

0.900.600.750.300.450.152.62.72.82.93.03.13.23.33.43.5

2.5

0 1.20

3.3VAUX_ VOLTAGE vs. OUTPUT CURRENT

3.3VO_ SENSE RESISTOR VOLTAGE vs. DIFFERENTIAL SWITCH VOLTAGE

V IN - V

3.3VSEN_ (V)

3.3V O _ C U R R E N T -L I M I T T H R E S H O L D (m V )

30343236384246444840 3.0

2.5

1.5

2.0

1.0

3.53.3VO_ VOLTAGE vs. OUTPUT CURRENT

OUTPUT CURRENT (A)

3.3

V O _ V O L T A G E (V )2

3.183.203.223.283.303.323.16

84

63.243.2620242228263034383640

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

5.0

5VO_ SENSE RESISTOR VOLTAGE vs. DIFFERENTIAL SWITCH VOLTAGE

V IN - V 5VSEN_ (V)

5V O _ C U R R E N T -L I M I T T H R E S H O L D (m V )

325VO_ VOLTAGE vs. OUTPUT CURRENT

OUTPUT CURRENT (A)

5V O _ V O L T A G E (V )1

4.824.844.864.884.904.924.80

5

23

4

4.944.964.98

5.005.02-12VO_ CURRENT FOLDBACK vs. DIFFERENTIAL SWITCH VOLTAGE

M A X 5915 t o c 04

V -12VIN - V -12VO_ (V)

-12V O _ C U R R E N T F O L D B A C K (m A )

2

50100

150

20025000

4

6

8

10

12

-12VO_ VOLTAGE vs. OUTPUT CURRENT

M A X 5915 t o c 03

OUTPUT CURRENT (mA)

-12V O _ V O L T A G E (V )50

-12.0-11.9-11.8-11.7-11.6-11.5-12.1

0250

100150

200+12VO_ CURRENT FOLDBACK vs. DIFFERENTIAL SWITCH VOLTAGE

M A X 5915 t o c 02

V +12VIN - V +12VO_ (V)

+12V O _ C U R R E N T F O L D B A C K (A )

2

0.10.30.50.70.91.1-0.1

046

81012+12VO_ VOLTAGE vs. OUTPUT CURRENT

M A X 5915 t o c 01

OUTPUT CURRENT (A)

+12V O _ V O L T A G E (V )

1.0

0.5

11.511.611.711.811.912.012.111.4

1.5

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Dual PCI 2.2 Hot-Swap Controllers 6_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V +12VIN = +12V, V 3.3VAUXIN = +3.3V, V -12VIN = -12V, V 5V = +5V, V 3.3V = +3.3V, R 5VSEN_= 0.005?, R 3.3VSEN_ = 0.005?, C 3.3VO_ =

2ms/div

TIME-TO-CHARGE GATE

(C GATE = 10nF)

ON_5V/div

3.3VGATE_

5V/div MAX5915 toc18

5VGATE_ 5V/div

200μs/div

TIME-TO-CHARGE GATE

(C GATE = 1nF)

ON_5V/div 3.3VGATE_

5V/div MAX5915 toc17

5VGATE_5V/div

100μs/div

TIME-TO-CHARGE GATE

(C GATE = 0.1nF)

ON_5V/div 3.3VGATE_

5V/div MAX5915 toc16

5VGATE_5V/div

M A X 5915 t o c 15

TEMPERATURE (°C)

-12V I N T E R N A L S W I T C H R O N (?)

6035-15100.10.20.30.40.50.60.70.80

-4085

-12V INTERNAL SWITCH R ON

vs. TEMPERATURE

M A X 5915 t o c 14

TEMPERATURE (°C)3.3V A U X I L I A R Y I N T E R N A L S W I T C H R O N (?)

603510-150.050.100.150.200.250.300.350

-40853.3V AUXILIARY INTERNAL SWITCH R ON

vs. TEMPERATURE

M A X 515 t o c 13

TEMPERATURE (°C)+12V I N T E R N A L S W I T C H R O N (?)

60

35

10

-15

0.050.100.150.200.250.300.350.400.450-40

85+12V INTERNAL SWITCH R ON

vs. TEMPERATURE

5VGATE_ AND 3.3VGATE_

DISCHARGE CURRENT vs. TEMPERATURE

TEMPERATURE (°C)

G A T E D I S C H A R G E C U R R E N T (μA )

60

35

10

-15

135140145150155160165170175180

130

-40

85

5VGATE_ AND 3.3VGATE_

CHARGE CURRENT vs. TEMPERATURE

TEMPERATURE (°C)G A T E C H A R G E C U R R E N T (μA )

60

35

10-159.511.513.515.517.519.521.523.525.527.57.5

-4085

3.3VAUX_ CURRENT FOLDBACK vs. DIFFERENTIAL SWITCH VOLTAGE

M A X 5915 t o c 10

V 3.3VAUXIN - V 3.3VAUXO_ (V)

3.3V A U X _ C U R R E N T F O L D B A C K (m A )

0.5

550600650700750800500

1.0

2.0

2.5

3.0

1.5

3.5

MAX5915/MAX5915A/MAX5916/MAX5916A

Dual PCI 2.2 Hot-Swap Controllers

_______________________________________________________________________________________7

Typical Operating Characteristics (continued)

(V +12VIN = +12V, V 3.3VAUXIN = +3.3V, V -12VIN = -12V, V 5V = +5V, V 3.3V = +3.3V, R 5VSEN_= 0.005?, R 3.3VSEN_ = 0.005?, C 3.3VO_ =

M A X 5915 t o c 27

TEMPERATURE (°C)

+12V I N P U T U V L O T H R E S H O L D (V )

603510-159.69.79.89.910.010.110.210.310.410.5

9.5

-4085

+12V INPUT UVLO

THRESHOLD vs. TEMPERATURE

3.3V AUXILIARY INPUT UVLO THRESHOLD vs. TEMPERATURE

M A X 5915 t o c 26

TEMPERATURE (°C)3.3V A U X I L I A R Y I N P U T U V L O T H R E S H O L D (V )

60

35

-15

10

2.62.72.82.9

3.03.13.23.32.5-40

853.3V AUXILIARY OUTPUT UNDERVOLTAGE

THRESHOLD vs. TEMPERATURE

M A X 5915 t o c 25

TEMPERATURE (°C)3.3V A U X I L I A R Y O U T P U T U N D E R V O L T A G E T H R E S H O L D (V )

60

35

10

-15

2.82.9

3.03.13.23.32.7-40

85 3.3V OUTPUT UNDERVOLTAGE THRESHOLD vs. TEMPERATURE

M A X 5915 t o c 24

TEMPERATURE (°C)

3.3V O U T P U T U N D E R V O L T A G E T H R E S H O L D (V )

60

35

-15

10

2.62.72.82.9

3.03.13.23.3

2.5-40

85

5V OUTPUT UNDERVOLTAGE THRESHOLD vs. TEMPERATURE

M A X 5915 t o c 23

TEMPERATURE (°C)5V O U T P U T U N D E R V O L T A G E T H R E S H O L D (V )

603510-154.434.484.534.584.634.684.38

-4085

+12V OUTPUT UNDERVOLTAGE THRESHOLD vs. TEMPERATURE

M A X 5915 t o c 22

TEMPERATURE (°C)+12V O U T P U T U N D E R V O L T A G E T H R E S H O L D (V )

60

35

10

-15

10.310.410.510.610.710.810.2

-40

85ON_ AND AUXON_ THRESHOLD

vs. TEMPERATURE

M A X 5915 t o c 21

TEMPERATURE (°C)

O N _ A N D A U X O N _ T H R E S H O L D (V )

603510-151.851.901.952.00RISING

FALLING

2.052.101.80

-4085

3.3VAUXIN SUPPLY CURRENT

vs. TEMPERATURE

M A X 5915 t o c 20

TEMPERATURE (°C)3.3V A U X I N S U P P L Y C U R R E N T (m A )

603510-150.250.500.751.001.251.501.752.002.252.500

-4085+12VIN SUPPLY CURRENT vs. TEMPERATURE

M A X 5915 t o c 19

TEMPERATURE (°C)+12V I N S U P P L Y C U R R E N T (m A )

60

35

10

-15

2.12.22.32.42.52.62.72.82.9

3.02.0-40

85

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Dual PCI 2.2 Hot-Swap Controllers 8_______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V +12VIN = +12V, V 3.3VAUXIN = +3.3V, V -12VIN = -12V, V 5V = +5V, V 3.3V = +3.3V, R 5VSEN_= 0.005?, R 3.3VSEN_ = 0.005?, C 3.3VO_ =

40ms/div

MAIN SUPPLY TURN-OFF WAVEFORMS

ON_ 5V/div +12VO_10V/div

MAX5915 toc36

PGOOD_5V/div

5VO_ 5V/div 200μs/div

TURN-ON DELAY

+12VIN 10V/div 3.3VAUXIN_

2V/div

3.3VAUXO_

2V/div

+12VO_10V/div ON_ = 5V AUXON_ = 5V

10ms/div

AUXILIARY SUPPLY TURN-ON WAVEFORMS

AUXON_5V/div

3.3VAUXO_

2V/div

PGOOD_ 5V/div

ON_ = 5.0V

10ms/div

MAIN SUPPLY TURN-ON WAVEFORMS

ON_ 5V/div

12VO_ 10V/div PGOOD_ 5V/div

5VO_ 5V/div AUXON_ = 5V

5VO_ SENSE RESISTOR VOLTAGE

vs. TEMPERATURE

TEMPERATURE (°C)

5V 0_ S E N S E R E S I S T O R V O L T A G E (m V )

60

35

-15

10

242220262834363840

-40

85

32303.3V AUXILIARY CURRENT FOLDBACK vs. TEMPERATURE

M A X 5915 t o c 31

TEMPERATURE (°C)3.3V A X I L I A R Y C U R R E N T F O L D B A C K (m A )

60

35

-15

10

475

550625700775850925-40

85

3.3VO_ SENSE RESISTOR VOLTAGE

vs. TEMPERATURE

TEMPERATURE (°C)

3.3V S E N S E R E S I S T O R V O L T A G E (m V )

60

35

10

-15

373941434535

-40

85

4749-12V OUTPUT CURRENT FOLDBACK vs. TEMPERATURE

M A X 5915 t o c 29

TEMPERATURE (°C)-12V O U T P U T C U R R E N T F O L D B A C K (m A )

6035-1510130

150170************-4085

M A X 5915 t o c 28

TEMPERATURE (°C)+12V O U T P U T C U R R E N T F O L D B A C K (A )

60

35

10

-15

0.70.80.91.01.11.20.6-40

85+12V OUTPUT CURRENT FOLDBACK vs. TEMPERATURE

MAX5915/MAX5915A/MAX5916/MAX5916A

Dual PCI 2.2 Hot-Swap Controllers

_______________________________________________________________________________________9

Typical Operating Characteristics (continued)

(V +12VIN = +12V, V 3.3VAUXIN = +3.3V, V -12VIN = -12V, V 5V = +5V, V 3.3V = +3.3V, R 5VSEN_= 0.005?, R 3.3VSEN_ = 0.005?, C 3.3VO_

=

-12VO_ CURRENT FOLDBACK

MAX5915 toc45

2ms/div

I -12VO_500mA/div

PGOOD_5V/div

-12VO_5V/div

-12VO_ IMMEDIATE SHORT-CIRCUIT RESPONSE

MAX5915 toc44

200ns/div

I -12VO_2A/div

PGOOD_5V/div

-12VO_5V/div

+12VO_ CURRENT FOLDBACK

MAX5915 toc43

2ms/div

I +12VO_5A/div

PGOOD_5V/div

+12VO_5V/div

+12VO_ IMMEDIATE SHORT-CIRCUIT RESPONSE

MAX5915 toc42

1μs/div

I +12VO_10A/div PGOOD_5V/div

+12VO_5V/div

AUXILIARY SUPPLY FAULT MANAGEMENT

MAX5915 toc41

400ms/div

5VO_+12VO_5V/div

3.3VAUXO_

5V/div PGOOD_5V/div

400ms/div

MAIN SUPPLY

AUTORESTART FAULT MANAGEMENT

+12VO_ 5V/div

5VO_ 2V/div MAX5915 toc40

3.3VAUXO_

5V/div PGOOD_5V/div

2ms/div

MAIN SUPPLY

LATCHED FAULT MANAGEMENT

+12VO_ 5V/div

5VO_ 2V/div MAX5915 toc39

3.3VAUXO_

5V/div PGOOD_5V/div

2μs/div

t DEG DELAY TIME

ON_ 5V/div 3.3VAUXO_

2V/div

MAX5915 toc38

PGOOD_5V/div

20ms/div

AUXILIARY SUPPLY TURN-OFF WAVEFORMS

ON_5V/div

3.3VAUXO_

2V/div

MAX5915 toc37

PGOOD_5V/div

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Dual PCI 2.2 Hot-Swap Controllers 10______________________________________________________________________________________

Typical Operating Characteristics (continued)

(V +12VIN = +12V, V 3.3VAUXIN = +3.3V, V -12VIN = -12V, V 5V = +5V, V 3.3V = +3.3V, R 5VSEN_= 0.005?, R 3.3VSEN_ = 0.005?, C 3.3VO_ =

3.3VAUXO_ CURRENT FOLDBACK

MAX5915 toc51

2ms/div

I 3.3VAUXO_

1A/div PGOOD_5V/div

3.3VAUXO_

2V/div

3.3VAUXO_ IMMEDIATE SHORT-CIRCUIT RESPONSE

MAX5915 toc50

2μs/div

I 3.3VAUXO_10A/div

PGOOD_5V/div

3.3VAUXO_

2V/div

3.3VO_ CURRENT LIMIT

MAX5915 toc49

2ms/div

I 3.3VO_10A/div

PGOOD_5V/div

3.3VO_2V/div 3.3VO_ IMMEDIATE SHORT-CIRCUIT RESPONSE

MAX5915 toc48

20μs/div

I 3.3VO_10A/div

PGOOD_5V/div

3.3VO_2V/div

FAIRCHILD FDS6670A

5VO_ CURRENT LIMIT

MAX5915 toc47

2ms/div

I 5VO_10A/div

PGOOD_5V/div

5VO_5V/div 5VO_ IMMEDIATE SHORT-CIRCUIT RESPONSE

MAX5915 toc46

40μs/div

I 5VO_10A/div

PGOOD_5V/div

5VO_5V/div FAIRCHILD FDS6670A

MAX5915A/MAX5916A 3.3VAUXO_ SHORT CIRCUIT

100ns/div

PGOOD_5V/div

3.3VAUXO_

1V/div

t RESP2

MAX5915A/MAX5916A 3.3VO_ SHORT CIRCUIT

100ns/div PGOOD_5V/div

3.3VO_1V/div t RESP2

MAX5915A/MAX5916A 12VO_ SHORT CIRCUIT

100ns/div

PGOOD_5V/div

12VO_5V/div

t RESP2

MAX5915/MAX5915A/MAX5916/MAX5916A Dual PCI 2.2 Hot-Swap Controllers

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Detailed Description

The MAX5915/MAX5915A/MAX5916/MAX5916A are cir-cuit-breaker ICs for hot-swap applications where a PCI card is inserted into a slot that is connected to a live backplane. Normally, when a card is plugged into a live backplane, the card’s discharged capacitors provide a low-impedance path that can momentarily cause the main power supply to collapse. Both devices provide startup current limiting and undervoltage/overcurrent monitoring of two separate PCI card slots. Current limit-ing and short-circuit protection are achieved using external n-channel MOSFETs on the +3.3V and +5V supply lines and internal MOSFETs on the ±12V and +3.3V auxiliary supply lines.

External sense resistors monitor the output currents of the +3.3V and +5V supplies. These external sense resistors adjust the overcurrent trip threshold. PCI stan-dards dictate maximum values for the supply power and total power drawn from the backplane. The maxi-mum power that any one PCI board can draw is 25W.Table 1 lists PCI standard maximum voltage, current,and power for each supply.

Table 1 illustrates that both the +5V and +3.3V supplies can draw up to 25W. Total combination of output power should be limited to 25W based on PCI standard.

Startup Mode

The +12V input powers the internal circuitry of these devices. The main supply outputs (3.3VO_, 5VO_,+12VO_, and -12VO_) can become active only after both of the following events have occurred:

?V +12VIN is above its undervoltage lockout (UVLO)

threshold.?

ON_ is driven high.

Figure 1 displays typical startup waveforms. The main supplies can be enabled without using the auxiliary supply; however, PGOOD_ remains in a low state if the

auxiliary supply is not used.

The auxiliary supply (3.3VAUXO_) is available after both of these events have occurred:?V 3.3VAUXIN is above its UVLO threshold.?

AUXON_ is driven high.

Normal Operation +3.3V, +5V,

±12V Outputs

The internal circuitry for these devices monitors the out-put voltage on all channels except the -12V supply. All outputs are monitored for overcurrent. An undervoltage condition occurs when any supply’s output voltage falls below the set undervoltage level. An overcurrent fault occurs when a monitored output current reaches the set overcurrent threshold. Each supply has its own overcurrent and undervoltage thresholds. If any of the monitored voltages fall below their respective under-voltage level, or if any of the monitored output currents reach their overcurrent threshold, for a time period,t DELAY , the controller disables the channel with the fault condition (see the Fault Management section).

External sense resistors monitor current through the external MOSFETs of the +3.3V and +5V outputs, while the current for the ±12V supplies are internally monitored.A fault condition on one of the main outputs causes all the channel’s main outputs to shut down after t DELAY and then either latch off (MAX5915/MAX5915A) or auto-matically restart after t RESTART (MAX5916/MAX5916A). A fault on any of the channel’s main outputs does not affect the channel’s auxiliary outputs.

Normal Operation +3.3V Auxiliary Output

Auxiliary output voltage and current are monitored inter-nally. The +3.3V auxiliary output is independent of the main outputs but the main outputs are dependent on the auxiliary outputs. Fault conditions on the main out-puts do not affect the auxiliary. A fault on the auxiliary supply causes the controller to disable all of the affected

Dual PCI 2.2 Hot-Swap Controllers 12

______________________________________________________________________________________

channel outputs, auxiliary and main. A fault condition occurs when the output voltage falls below the set undervoltage threshold or the output current reaches the overcurrent threshold. When a fault occurs, all supplies of the affected channel are disabled after a time period t DELAY . All outputs are automatically restarted after a time equal to t RESTART . This reset is built into all devices.

Current Limits

All supplies are protected against output overcurrent or short-circuit conditions. The MAX5915/MAX5915A and MAX5916/MAX5916A employ a “brickwall” current limit on the +3.3V and +5V supplies and a current-foldback scheme on the ±12V and +3.3V auxiliary supplies.Brickwall

A brickwall current limit protects the +3.3V and +5V main supplies by limiting the load current. The external

sense resistors and the current-limit threshold set the brickwall current limits. A fault occurs when the load current reaches the brickwall limit. The main outputs shut down after t DELAY if the fault remains. The brick-wall feature limits inrush current caused by positive supply voltage steps.

Foldback

The ±12V and +3.3V auxiliary supplies employ an internal current-foldback scheme. The MAX5915/MAX5915A/MAX5916/MAX5916A gradually limit the load current once the current-foldback threshold is reached. If the overcurrent condition lasts longer than a fast tran-sient, the output current is reduced to the foldback cur-rent limit and remains at that level for t DELAY unless the overcurrent condition is cleared. See the Typical Operating Characteristics .

MAX5915/MAX5915A/MAX5916/MAX5916A

Dual PCI 2.2 Hot-Swap Controllers

______________________________________________________________________________________13

Figure 1. Startup Waveforms

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Input Undervoltage Lockout

UVLO prevents these devices from turning on internal/external MOSFETs until the input voltage exceeds the lockout threshold. The UVLO protects the MOSFETs from insufficient gate-drive voltage. Figure 2 shows that if an input undervoltage condition exists for more than t DEG,UVLO , the outputs are disabled and PGOOD_ goes low immediately. The time delay t DEG,UVLO is negative edge delayed and acts as a deglitch.

Fault Management

When a fault is detected on one of the main outputs, the MAX5915/MAX5915A/MAX5916/MAX5916A disable the channel outputs after t DELAY . A fault occurs when any of the output voltages fall below their output undervoltage threshold or any of the output currents exceed their out-put overcurrent threshold. PG OOD_ pulls low if a fault persists for more than t RESP . The channel with the fault is disabled after t DELAY . The MAX5915/MAX5916 are avail-able with a response time of 1.5ms (t RESP ). The MAX5915A/MAX5916A offer a response time of 100ns (t RESP2).If the fault is removed before t DELAY , the chan-nel remains on and PGOOD_ pulls high immediately.

Latched Fault Protection

The MAX5915/MAX5915A latch off the appropriate channel’s main outputs. Toggling +12VIN or ON_restarts the main outputs. Figure 3 outlines the logic for the main and auxiliary shutdown control of the MAX5915, while fault handling is shown in Figures 5and 6.

Autoretry Fault Protection

The MAX5916/MAX5916A automatically restart the out-puts after t RESTART . The MAX5915/MAX5915A/MAX5916/MAX5916A handle faults on the auxiliary out-puts by automatically restarting the appropriate chan-nel. Figure 4 outlines the logic for the main and auxiliary shutdown control of the MAX5916, while fault handling is shown in Figures 6 and 7.

Output Overcurrent

External sense resistors monitor the current on the +5V and +3.3V outputs, while the +3.3V auxiliary and ±12V output currents are monitored internally. Figures 5, 6,and 7 show overcurrent fault management for the MAX5915/MAX5915A/MAX5916/MAX5916A.

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Figure 2. Input UVLO Fault Management in the MAX5915/MAX5915A/MAX5916/MAX5916A

Output Undervoltage

The output voltages on all supplies, except the -12V supply, are monitored for undervoltage. Output under-voltage fault management is identical to the output overcurrent fault management. Figures 5, 6, and 7 can be used to illustrate undervoltage faults on the MAX5915/MAX5915A/MAX5916/MAX5916A.

Thermal Shutdown Control

The MAX5915/MAX5915A/MAX5916/MAX5916A feature internal thermal protection. Two thresholds detect when the device is overheated. If the first threshold is reached,the channel that is in overcurrent shuts down. If the sec-ond thermal threshold is reached, the entire device shuts down. The device cannot be restarted until the thermal condition is cleared. For the MAX5915, the main chan-nels turn back on after +12VIN or ON_ is toggled. For the MAX5916, the main channels turn back on after t RESTART . The auxiliary channels for the MAX5915/MAX5915A/MAX5916/MAX5916A restart after t RESTART .

PGOOD_ Operation

The MAX5915/MAX5915A/MAX5916/MAX5916A incor-porate a PGOOD_ output to report when power is good to a microprocessor or controller. PGOOD_ remains low if the auxiliary outputs are not powered, for PCI and compact PCI systems where the 3.3VAUX is not avail-able. Connect 3.3VAUXIN to 3.3VIN and connect AUXON_ to ON_ to allow PG OOD_ to transition high when the main supplies are available. The open-drain structure of PGOOD_ requires an external pullup resis-tor (see the Functional Diagram ). Figure 8 shows the internal logic of the PGOOD_ output.

MAX5915/MAX5915A/MAX5916/MAX5916A

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Figure 3. Main and Auxiliary Supply Shutdown Control Logic for MAX5915/MAX5915A

M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

Applications Information

Component Selection

External MOSFETs

Select the external n-channel MOSFETs according to the application’s current requirement. Limit switch power dissipation by choosing a MOSFET with an R DS(ON)low enough to have a minimum voltage drop at full load.High R DS(ON)causes output ripple if the board has pulsing loads. High R DS(ON)can trigger an external undervoltage fault at full load. Determine the MOSFET’s power rating requirement to accommodate a short-cir-cuit condition on the board during startup (see the External MOS FET Thermal Considerations section).Table 3 lists MOSFET and sense resistor manufacturers.

Sense Resistors

The overcurrent sense voltage threshold on the +3.3V output is 46mV and 31mV on the +5V output. Choose a sense resistor using the following equation:

R SENSE = (V-ILIM / I LOAD )where I LOAD is the brickwall current limit for the output.Choose the sense resistors’ power rating to accommo-date the overload current:

P SENSE = (I LOAD )2 x R SENSE

Additional External Gate Capacitance

Connecting an external capacitance from the gates of the external MOSFETs to GND slows the turn on of the +5V and +3.3V supplies.

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Figure 4. Main and Auxiliary Supply Shutdown Control Logic for MAX5916/MAX5916A

Large capacitive loads can cause a problem when inserting discharged PCI cards into the live backplane. If the time needed to charge the capacitance of the board is greater than the typical startup time, 50ms, a fault can occur after startup.

The MAX5915/MAX5915A/MAX5916/MAX5916A are able to withstand large capacitive loads due to their long start-up time. Each supply has its own current-limit threshold. Calculate the maximum load capacitance as follows:

C BOARD< 50ms x I_, LIM/ V SUPPLY

Input Transients The +12V and +3.3VAUX supplies must be above their respective UVLO thresholds before startup can occur. Input transients can cause the input voltage to sag below the UVLO threshold. The MAX5915/MAX5915A/ MAX5916/MAX5916A reject input transients that are shorter than t DEG, UVLO.

External MOSFET Thermal

Considerations The power dissipation of the external MOSFET is low when it is on, P D= I LOAD2x R DS(ON). A considerable amount of power is dissipated during startup and con-tinuous short-circuit conditions. The design must take into consideration the worst-case scenario.To take full advantage of the switch response time to an output fault condition, keep all traces as short as possi-ble and maximize the high-current trace dimensions to reduce the effect of undesirable parasitic inductance. Place the MAX5915/MAX5915A/MAX5916/MAX5916A close to the PCI card’s connector. Use a ground plane to minimize impedance and inductance. Minimize the current-sense resistor trace length and ensure accurate current sensing with Kelvin connections (Figure 9). When an output is short circuited, the voltage drop across the external MOSFET becomes large. Hence the power dissipation across the switch and die tempera-ture both increase. An efficient way to achieve good power dissipation on a surface-mount package is to lay out two copper pads directly under the package on both sides of the board. Connect the two pads to the ground plane through vias, and use enlarged copper mounting pads on the topside of the board.

Chip Information TRANSISTOR COUNT: 1021

PROCESS: BiCMOS MAX5915/MAX5915A/MAX5916/MAX5916A Dual PCI 2.2 Hot-Swap Controllers

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M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

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Figure 5. Main Outputs Overcurrent Fault Management in the MAX5915/MAX5915A

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M A X 5915/M A X 5915A /M A X 5916/M A X 5916A

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Figure 7. Main Outputs Overcurrent Fault Handling in the MAX5916/MAX5916A