Linear Technology LTC4245CUHF Manuale utente

LTC4245CUHF

DESCRIPTION

Demonstration circuit 985 showcases

the LTC

4245 Hot Swap™ controller

with I

C™ compatible monitoring in a

CompactPCI™ (CPCI) application. The

LTC4245 resides on the plug-in board,

DC985A-A, which carries a female CPCI

connector. This board plugs into the

male connector on the backplane

board, DC985A-B. The plug-in board

also carries the four n-FET switches

and sense resistors required for hot

swap. LEDs provide visual indication

of the important signals and volt-

ages.

The board can be configured to work

in a PCI Express™ application by ad-

justing a few jumpers. To access the

powerful monitoring features of the

LTC4245, the I

C port on the back-

plane board must be connected to a

DC590 board (available separately).

The LTC4245 can then be controlled

with evaluation software running on a

host PC.

Design files for this circuit board

are available. Call the LTC factory.

and LTC are registered trademarks of Linear Technology

Corporation. Hot Swap and QuickEval are trademarks of Linear

Technology Corporation. All other trademarks are the property

of their respective owners.

PERFORMANCE SUMMARY

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

Input Supply Range

+12V IN

+5V IN

+3.3V IN

-12V IN

MOSFET Q1-Q4 On, TVS Z1-Z4 Off

CFG Jumper, JP4, at LOW or FLOAT

CFG Jumper, JP4, at HIGH

CFG Jumper, JP4, at LOW

CFG Jumper, JP4, at FLOAT or HIGH

10.8

4.5

2.9

-10.8

3.3

-12

-15

OUT,CB

Circuit Breaker Trip Current

+12V OUT

+5V OUT

+3.3V OUT

-12V OUT

After Start-Up

R1 = 8mΩ, 1%

R2 = 3.5mΩ, 1%

R3 = 2.5mΩ, 1%

R4 = 40mΩ, 1%

5.5

6.4

8.9

0.99

6.25

7.1

1.25

6.9

7.9

11.1

1.52

QUICK START PROCEDURE

Verify that the jumpers are set as

follows:

Backplane board: JP1 BD_SEL#: LOW;

JP2 PCI_RST#: HIGH

Plug-in board: JP3 ON CONFIG: AUTO;

JP5 PGI: HIGH; JP4 CFG: LOW if us-

ing all four supplies, FLOAT if us-

ing 12V, 5V and 3.3V, HIGH if using

12V, and two 3.3V.

DEMO CIRCUIT

985

QUICK START GUIDE

LTC4245CUHF

Multiple Supply Hot Swap Controller

with I

C Compatible Monitoring

LTC4245CUHF

Mate the plug-in board with the

backplane board.

With the power off, connect the in-

put supplies and output loads as

shown in Figure 1. If -12V supply

is not being used, ground -12V IN

and -12V OUT turrets.

Turn on power at the inputs. Check

that the LTC4245 automatically

turns on. LEDs D1 to D4 indicate

when input power is applied, and D5

to D8 show when it is available at

the output. If the output voltages

are within tolerance, HEALTHY#

green LED, D9, turns on, and

LOCAL_PCI_RST# red LED, D10, stays

off. If the outputs remain off,

check the fault registers (Step 8).

To access the ADC data or to con-

trol the LTC4245 through I

C, in-

stall the QuickEval™ System soft-

ware on a computer with an avail-

able USB port. The download website

is http://www.linear.com/software.

Open the QuickEval software. If al-

ready installed, update the soft-

ware to obtain the LTC4245 driver.

Connect DC590 to the PC with a USB

cable as shown in Figure 2. Connect

the backplane board I

C port, P2,

to the DC590 USB controller board

using the supplied 14-conductor

ribbon cable. Upon connection,

QuickEval will identify the DC985,

and open the LTC4245 interface

software window as shown in Figure

In the software, choose the CFG Pin

option that matches the CFG jumper,

JP4, setting on the board. Click

the Auto Find button in the I2C Ad-

dress section, so the software can

figure out the I

C slave address of

the LTC4245. After that, click the

START button to get a continuous

update of the LTC4245 internal reg-

isters. The software window dis-

plays the MOSFET and overall

status.

Click Show Registers button for an

expanded view of all the registers

(Figure 4). The check-boxes can be

used to selectively set or reset

the corresponding register bit.

Figure 1.

Proper Measurement Equipment Setup

LTC4245CUHF

USB

DC985A-B

DC590A

14-WIRE

RIBBON

CABLE

Figure 2.

QuickEval Setup

Figure 3.

Default LTC4245 QuickEval Interface

Figure 4.

LTC4245 QuickEval Interface with Register Display

LTC4245CUHF

HARDWARE SETUP

BOARD LAYOUT

The top of the plug-in board contains

the core Hot Swap controller and as-

sociated components, along with LEDs.

Also on top are various configuration

jumpers and all connection turrets.

The large turrets may be removed to

permit installation of up to 12 gauge

wire for direct, low resistance con-

nections to the board. None of the

turrets are swaged.

The bottom of the boards contains

components for software identifica-

tion of the board, LED current limit-

ing resistors, the CPCI connector

(J1), and a spare sense resistor.

Also on the bottom is the LTC4245

INTV

bypass capacitor, C11, and the

supply input and output capacitors.

Except for C11, the other components

are largely unrelated to the core ap-

plication and are included for the

purposes of the demo board itself.

The spare 50msense resistor, R1OPT,

can be used to replace the 8mresis-

tor (R1) on the 12V supply to lower

its current limit to CPCI levels.

The boards are designed with two

ground planes, on layers 2 and 3.

Layer 2 is a small signal ground

plane which picks up ground for

LTC4245, the small SGND turrets, C11,

CSS, CT, as well as I

C and configu-

ration jumper related grounding.

Layer 3 is reserved for large signal

grounding, including capacitors on

supply inputs and outputs, large PGND

turrets, input and output LEDs, and

input clamps and snubbers. These two

ground planes join at the CPCI con-

nector ground pins.

HIGHER CURRENT ON ±12V

The CPCI connector pin DC current

should be limited to 1A per pin. The

12V supply has 1 pin; 5V has 2 long

and 6 medium pins; 3.3V has 2 long

and 8 medium pins; -12V has 1 medium

pin. The Si7880DP n-FET used on all

four supplies is rated to 18A at room

temperature.

The circuit breakers for the four

supplies are set as shown in the Per-

formance Summary table. It is dic-

tated by the tolerance on the circuit

breaker trip sense voltage and the

sense resistor.

If the load current on the 12V supply

is more than 1A, the +12V IN turret

on the plug-in card should be used to

supply the input current. Otherwise

the 12V connector pin may be damaged.

To use higher load currents on -12V

OUT use the -12V IN turret on the

plug-in card for the input power sup-

ply. The sense resistor R4 will also

need to be replaced with a value

lower than the installed 40m.

PCI EXPRESS APPLICATION

For PCI Express current levels, use

the +12V IN turret on the plug-in

card to supply input power. Set the

CFG pin jumper (JP4) HIGH so a 3.3V

supply can be used at the +5V IN tur-

ret. Ground the -12V IN and -12V OUT

turrets. If needed, modify the sense

resistors (R1 to R3) to adjust the

circuit breaker levels.

GPIO1 (A/D INPUT)

The GPIO1 turret is pulled up to 3.3V

with a 100kresistor. It can be used

to measure voltages in a 0V to 2.56V

LTC4245CUHF

range. The result is displayed in the

ADC Data section of the LTC4245 soft-

ware window on the computer.

PRECHARGE

As soon as the LTC4245 3V

pin is

powered up, the PRECHARGE turret can

source up to 70mA at 1V. This is used

in CPCI to pre-bias the bus I/O lines

during insertion. The turret facili-

tates hooking up the PRECHARGE pin to

external circuitry.

INTVCC

INTVCC was included on the LTC4245 to

allow bypassing of the internal 5.5V

supply rail for superior noise immu-

nity. It is also permissible to steal

a small current of up to 3mA off the

INTVCC pin to bias address pins or

ancillary circuits. A turret is pro-

vided for connections to INTVCC.

CONNECTORS

J1: Plug-in card female CompactPCI

connector. This connector mates with

the P1 connector on the backplane

board to allow power and control sig-

nals to flow to the LTC4245 and the

supply outputs. The connector util-

izes guiding features to ensure cor-

rect polarized mating.

P1: Backplane card male CompactPCI

connector. There are three lengths of

pins on this connector. Long 5V, 3.3V

and GND pins provide early power to

the LTC4245. Majority of the pins are

medium length. The short BD_SEL# pin

mates last, and provides the turn-on

signal to the LTC4245.

P2 I

C PORT: Connector for DC590 I

adapter card. This card converts a

computer’s USB port to I

C. If P2 is

not connected, the turret terminals

SDA and SCL can be connected directly

to an I

C bus.

JUMPERS

JP1 BD_SEL#: Connects BD_SEL# back-

plane signal either to ground or

leaves it floating, whereby it will

be pulled up by the 1.2kon the

plug-in card to 5V. In the latter

case, the BD_SEL# turret can be con-

nected to external insertion-detect

logic to initiate turn-on of LTC4245.

Removing and reinstalling the shunt

at LOW will cycle power to the board

and also reset the LTC4245 fault reg-

isters.

JP2 PCI_RST#: Sets the backplane re-

set signal PCI_RST# high, low or

floating. When floating, the PCI_RST#

turret should be driven with an ex-

ternal signal. This jumper will af-

fect the LOCAL_PCI_RST# output of the

LTC4245 (LED D10).

JP3 ON CONFIG: At start-up the

LTC4245 operates in one of two modes:

in AUTO mode it turns on when BD_SEL#

goes low; in I2C mode it waits for an

C turn-on command, even after

BD_SEL# goes low, to turn-on the

switches.

JP4 CFG: Sets the CFG pin high, low

or floating. This affects the input

supply range requirement for FET

turn-on. For a CPCI application re-

quiring all four supplies, set it

low. Refer the Performance Summary

table and the datasheet for more de-

tails.

JP5 PGI: Sets the PGI pin of the

LTC4245 high, low or floating. When

floating, the PGI turret should be

driven with an external signal, such

as the RESET# output of an external

supply monitor. Setting the PGI pin

LTC4245CUHF

low can lead to a PGI fault causing

all FETs to be turned off.

JP6 to JP9 ADR0 to ADR3: Selects 1 of

32 possible addresses for the LTC4245

C interface by strapping the ad-

dress pins high, low or allowing them

to float. An address table is shown

in the datasheet and the Help menu of

the evaluation software. The software

can automatically scan and identify

the I

C address, regardless of the

pin setting.

LEDs

D1 to D8: D1 to D4 indicate if the

input supplies are high. D5 to D8

light up when the supply outputs

power up, after the FET switches turn

on.

D9 HEALTHY#: This should light up at

the end of the start-up timing cycle

after all the supply outputs power

up. It will turn off as soon as any

FET switch is turned off or if any

output falls out of tolerance.

D10 LOCAL_PCI_RST#: This LED normally

flashes briefly during start-up and

power-down. This is because it is

powered off +3.3V OUT and the pin is

released at the end of the start-up

timing cycle. It will be lit continu-

ously if +3.3V OUT is high and

PCI_RST# is set low with JP2.

D11 ALERT#: The ALERT# pin pulls low

and turns on this LED if a fault oc-

curs and that fault’s alert is en-

abled in the ALERT register. The

alert can be cleared either by reset-

ting bit B3 in the ALERT register or

writing to the LTC4245 alert response

address (ARA).

SOFTWARE SETUP

Communicating with the LTC4245 I

interface requires the QuickEval Sys-

tem software and a DC590 board. The

QuickEval software is available from

the website www.linear.com/software.

The QuickEval software talks to the

DC590 board through the USB port of

the PC. The DC590 is connected to the

C port (P2) on the DC985A-B with

the supplied 14-wire ribbon cable

(Figure 2). When connected, the

QuickEval software identifies the

DC985 and brings up the LTC4245 in-

terface as shown in Figure 3. When

experiencing problems with the soft-

ware, try unplugging and plugging the

DC590 board from the PC. Also refer

the DC590 Quick Start guide.

C ADDRESS SELECTION

Select in the drop down list box the

Write address byte of the LTC4245

that is to be communicated with. The

address pins to I

C address map can

be found in the Help menu. Easier

still, the Auto Find button will scan

through the 32 individual LTC4245 ad-

dresses and list which addresses re-

sponded with an acknowledge. If mul-

tiple LTC4245s are on the bus lines,

the Mass Write address 2Eh can be se-

lected to write to all LTC4245s at

the same time. The ARA button sends

the Alert Response protocol address

and displays the address of the de-

vice holding its ALERT# pin low.

5V ADC LSB AND -12V ON CONTROL

Select the radio button that corre-

sponds with the CFG pin jumper, JP4,

LTC4245CUHF

setting on the plug-in board. Refer

to Table 1 for the effect of this

setting on software parameters.

CFG PIN 5VIN LSB 5VOUT LSB

-12V ON/OFF

CONTROL BIT

LOW 22mV 22mV D3

FLOAT 22mV

22mV D0

HIGH 15mV 15mV D0

Table 1: CFG Pin Setting

START AND REFRESH BUTTONS

Click on the START button to enable a

timer that continuously updates the

interface with the latest data from

the LTC4245. This button will display

STOP when the timer is enabled. Click

on STOP to stop the timer. Click on

REFRESH for a single update.

ADC DATA DISPLAY

The data read from the LTC4245 ADC

registers I to U is displayed in an

easy to read format by multiplying

the data with the LSB size and dis-

playing it as a voltage. The current

sense values can be displayed as ei-

ther a voltage drop (default) or a

current. The sense resistance values

cannot be edited while the software

is in polling mode. There is also an

option for displaying output power

instead of output voltage.

The bits of registers A to H are

shown in detail by clicking on the

Show Registers button (Figure 4).

Checking a box to the left of each

bit of the Read/Write registers sets

the respective bit, while unchecking

a box clears the bit. The bit status

is shown to the right of each bit af-

ter every refresh of the interface.

In the Register List box a bit map of

all the registers is shown and is up-

dated with each refresh of the inter-

face.

The Register Read/Write section al-

lows for the user to enter and write

data to a particular register. Select

the register to be written to in the

drop down menu. Enter the data in hex

and click on Write to send the data,

and then click Read to verify the

write. Read data is displayed both in

hex and decimal.

MOSFET STATUS AND CONTROL

The MOSFET status is shown with a

display, which is colored:

■

Green, when the FET On Status bit

(D4 to D7) is high; the FET control

button will read “Turn Off”

■

Clear, if FET On Status bit is low

and the corresponding FET On con-

trol bit (D0 to D3) is also low;

the FET button will read “Turn On”

■

Red, if FET On Status bit is low

and the corresponding FET On con-

trol bit is also high; the FET con-

trol button will read “Clear Fault”

The “Turn On” control button sets the

corresponding supply’s FET On control

bit high, while “Turn Off” clears it

to logic low. As mentioned before, if

CFG pin radio button is set to FLOAT

or HIGH, the -12V MOSFET is con-

trolled with the 12V FET On control

bit, D0, instead of D3. “Clear Fault”

button writes zeros to the FAULT1 and

FAULT2 registers, in an attempt to

turn-on the MOSFETs by clearing fault

bits. If a fault is still present,

then that fault bit will be set again

by the LTC4245, thus preventing turn-

on.

LTC4245CUHF

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