Linear Technology DC2442A Manuale utente

dc2442af

DEMO MANUAL DC2442A

DESCRIPTION

LTC4282

Low Stress Staged Start

200A Hot Swap Controller

Demonstration circuit 2442A features the LT C

4282 high

current Hot Swap controller. The LTC4282 is well suited

to high power applications because the precise monitor-

ing capability and accurate current limiting reduces the

extremes in which both loads and power supplies must

safely operate. Nonvolatile configuration allows for flex-

ibility in the autonomous generation of alerts and response

to faults. The LTC4282 provides a rich set of features to

support Hot Swap applications including:

n 12- to 16-Bit ADC Monitors Current, Voltage, Power

and Energy

n Controls Two Sets of Parallel MOSFETs for High

Current Applications

L, LT, LTC, LTM, Linear Technology, the Linear logo and LTpowerPlay are registered

trademarks of Linear Technology Corporation. All other trademarks are the property of their

respective owners.

n I2C/SMBus Interface

n Nonvolatile Configuration and Logging Functions

n Generates Alerts on ADC Measurements Outside

Limits

n Software Adjustable Current Limit with Foldback

n Three General Purpose Input/Outputs

Available in a 32-pin 5mm × 5mm QFN package, the

LTC4282 is showcased on DC2442A configured in a

“Low Stress Staged Start”configuration for a 12V/200A

application.

Design files for this circuit board are available at

http://www.linear.com/demo/DC2442A

Figure 1. Basic Test Setup

VARIABLE

POWER

SUPPLY

TEST

LOAD

dc2442a F01

dc2442af

DEMO MANUAL DC2442A

QUICK START PROCEDURE

Table 1. Power Input and Output Connections

NOMENCLATURE CONNECTOR DESCRIPTION

+12VIN E1 +12V Power In

+12VOUT 200A E2 +12V Power Out

GND E21 (Banana) Power Supply Common

Table 2. Test Points, Turrets

NOMENCLATURE TURRET DESCRIPTION

GPI01 E3 GPIO1 Pin I/O

INTVCC E4 Internal VCC

+12VOUT E5 +12VOUT Monitor

+12VIN E6 +12VIN Monitor

ON (SHORT PIN) E7 ON Pin Monitor/Input

SCL E8 I2C Serial Clock Input

GND E9, E10, E15, E17 Ground

SDA E11 I2C Serial Data Input/Output

ALERT E12 ALERT Pin

GPIO2 E13 GPIO2 Pin I/O

GPIO3 E14 GPIO3 I/O

EXT 5V E16

TIMER E18 TIMER Pin

UV E19 UV Pin

OV E20 OV Pin

GATE2 E23 GATE 2 Pin

GATE1 E22 GATE 1 Pin

PERFORMANCE SUMMARY

Specifications are at TA= 25°C

PARAMETER CONDITIONS VALUE

Input Supply Voltage Range 2.9V to 33V

Nominal Operating Voltage 12.0V

Overvoltage Lockout Nominal 15.0V

Undervoltage Lockout Nominal 11.1V

Output Current Limit Nominal 207A

Maximum Load Capacitance Nominal 20,000μF

Timer Expiration Period Nominal 1.4ms

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DEMO MANUAL DC2442A

Table 3. LED Indicators

NOMENCLATURE LED DESCRIPTION

IN D1 (Green) Input Power Indicator

OUT D2 (Green) Output Power Indicator

ALERT D5 (Red) ALERT Pin Logic Low

SCL D6 (Green) Serial Clock Active

SDA D7 (Green) Serial Data Active

GPIO3 D8 (Green) GPIO3 Logic Low

GPIO2 D9 (Green) GPIO2 Logic Low

Table 4. Jumpers

NOMENCLATURE JUMPER DESCRIPTION

CLK, INT, EXT JP1 Internal/External Clock Select

ON, INTVCC, FLOAT, GND JP2 ON Input Select, VCC, Float (External), GND

ADR0, H, NC, L JP3 Address Pin ADRO Select

ADR1, H, NC, L JP4 Address Pin ADR1 Select

ADR2, H, NC, L JP5 Address Pin ADR2 Select

WRITE PROTECT, LOCK, WRITE JP6 Write Protect for EEPROM

Table 5. Connectors

NOMENCLATURE CONNECTOR DESCRIPTION

DC590 J1 Connection for DC590

DC1613 J2 Connection for DC1613

QUICK START PROCEDURE

dc2442af

DEMO MANUAL DC2442A

Operating Principles

The LTC4282 is a low voltage, high current Hot Swap

controller that has a 2.9V to 33V operating range and

a 45V absolute maximum operating voltage for the VDD

pin. The DC2442A is populated for +12V operation and is

configured for a “Low Stress Staged Start”configuration.

For details on this configuration refer to the “Low Stress

Staged Start Configuration” section.

The DC2442A is populated with a total of eight 0.9mΩ

MOSFETs and one 11mΩ MOSFET in a LFPAK package.

A total of sixteen 1mΩ sense resistors are used, provid-

ing typically 207A of load current. The current limit and

circuit breaker thresholds can be adjusted by changing

the sense resistors R25, R30, R35, R41, R47, R53, R58,

R63, R80, R85, R90, R95, R100, R105, R110 and R115

and/or the value of ∆VSENSE via registers in the LTC4282.

On the DC2442A, the LTC4282 is preprogrammed for a

∆VSENSE of 12.5mV to reduce power dissipation in the

sense resistors at such high currents;it has not been

tested for ∆VSENSE greater than 12.5mV. It is strongly

advised not to adjust this threshold on the DC2442A

without careful consideration of the power dissipation in

the sense resistors.

Low Stress Staged Start Configuration

In the Low Stress Staged Start configuration, the dual

gates are taken advantage of where one channel works as

a trickle charging channel, responsible for trickle charg-

ing the output during turn on and the other channel is the

bypass channel which turns on only when the power to

the output is good (within 0.7V of the input). The power

good signal is used to hold the bypass channel gate off, by

keeping it in artificial current limit, until the trickle channel

has powered up the load. The start-up trickle MOSFET Q1

is a compact, inexpensive device with small SOA and is

configured for a low current limit with a GATE capacitor

to limit inrush current. When the load is fully charged and

the start-up MOSFET is fully enhanced, the power good

signal is asserted, releasing the bypass channel’s sense

pin and enabling it. The bypass side has a high current

limit to deliver the full load current, and uses low RDS(ON),

low SOA switching regulator class MOSFETs. The TIMER

capacitor is selected for a short time within the SOA of

the bypass MOSFETs.

This architecture minimizes the cost of MOSFETs toachieve

a given load current and RDS(ON). However, with the short

current limit time, it has limited ability to ride through a

load surge in current limit or input voltage steps, and due

to the low start-up current cannot start up a resistive load

such as a heating element or incandescent lamp.

QUICK START PROCEDURE

dc2442af

DEMO MANUAL DC2442A

QUICK START PROCEDURE (WITHOUT SOFTWARE)

DC2442A is easy to set up to evaluate the performance of

the LTC4282. Refer to Figure 1 for proper measurement

equipment setup and follow the procedure below.

WARNING: The DC2442A is capable of operation in excess

of 200A. At this current and power level, there is a danger

of serious personal injury and equipment damage if proper

techniques are not used. All cabling between the power

supply and the load should be capable of handling the

current levels used.

Additionally, the high currents and fast transientscan cause

unexpected voltage drops in cables connecting the test

equipment to the DC2442A due to parasitic resistance and

inductance. The cable drops may cause sneak paths for

the current via various cables and scope probes causing

unexplained ringing, distorted oscilloscope waveforms,

voltage and current spikes, and signals appearing to be

below ground.

A common sneak path for current is the third wire ground

used on power cords of test equipment in use. Using

ground lifting connectors at the wall outlet won’t neces-

sarily alleviate these effects since most equipment has

line-bypassing capacitors between the mains voltage and

local chassis ground. Isolating test equipment using line

isolation transformers with low primary to secondary

capacitance is recommended.

Another method to remove these artifacts is to use dif-

ferential scope probes to probe connections between the

signal to be observed and a local ground referenced to

the point being measured.

Also be careful to not allow an open ground from the

power supply or load to cause return current through the

grounds of the various devices connected to the demo

board. This can cause damage to the equipment as well

as cause a fire hazard.

The DC2442A is setup to operate in a 12V system at current

levels up to 200A. At 200A, the bypass channels MOSFETs

are dissipating only 500mW each. No additional airflow is

needed for continuous operation, the totaltemperature rise

of the board averaging around 70°Cwith no airflow. If the

MOSFET count is reduced, ensure that there is sufficient

airflow to manage thermal dissipation.

Figure 2. Demo Board Temperature at 73°C After 10

Minutes of Continuous Operation at 200A with No Airflow

Jumper Positions

JUMPER NAME POSITION

JP1 CLK EXT

JP2 ON INTVCC

JP3 ADR0 NC

JP4 ADR1 NC

JP5 ADR2 NC

JP6 WRITE PROTECT LOCK

dc2442af

DEMO MANUAL DC2442A

Powering Up

Connect power supply capable of 220A at 0V to 20V to the

12V input as shown in Figure 1. Verify that the cabling,

shown in extra bold lines, is capable of carrying 200A

safely. The GND connection does not handle high current

so no high current cabling is required.

Generally, an electronic load will be used. If this is true, use

it in the constant resistance mode. Use in constant current

will prevent start-up because of current foldback in the

LTC4282. To minimize power dissipation in the MOSFETs,

current is initially limited to approximately 30% of the full

current limit that is available when the output voltage is

above 10V. If a constant current load is used and set to

200A, the LTC4282 will not start-up and a current fault

will be reported.

UV/OV Thresholds

With no load on the output, slowly increase the voltage

on the input to the board. Observe the input voltage when

LED D2 (OUT) illuminates. This voltage should be between

10.7V and 11.4V. Continue increasing voltage until D2 is

extinguished.This shouldoccur between14.4V and15.3V.

Output Voltage Slew Rate

With no load connected, observe the output voltage be-

tween turret +12VOUT (E5), and GND. Apply 12V to the

+12VIN connector. The output voltage should slew from

0V to 12V in 10ms to 25ms.

Output Current Limit

Turn off power supply and connect electronic load to the

DC2442 as shown in Figure 1. Disable electronic load.

Adjust power supply to 12V and verify its current level is

set to > 200A.

Slowly increase conductance of the electronic load while

monitoring current. As the load increases to around 200A,

the output voltage and current will fall to zero. Note the

current where this occurs. This should be between 200A

to 210A.

Ability to Charge Output Capacitor

Turn off power supply and disconnect electronic load.

Replace load with a 20,000μF capacitor rated at 15V or

greater. Turn on power supply and observe that the output

voltage rises to 12V indicating the DC2442 has connected

to theload andsuccessfully chargedthe outputcapacitance.

This should happen within 400ms to 500ms.

QUICK START PROCEDURE (WITHOUT SOFTWARE)

LTpowerPlay

is a convenient PC software GUI that gives

complete access to the registers of the LTC4282 and many

other Linear Technology Power System Management parts.

Use it in off-line mode to build a system configuration file

even with no hardware plugged-in, and use it with hard-

ware connected to configure and debug your application.

TpowerPlay communicates using the I2C bus in the demo

system (covered in this manual), or in your real-world

product environment. It provides unprecedented control

over the Linear Technology chips on the I2C bus. Use it

during board bring-up to tune and optimize the power

system parameters. Use it during system debug to view

critical system information and troubleshoot board design

or manufacturing issues. LTpowerPlay includes extensive

help and documentation under the Help menu. Online help

includes quick-start videos and tutorials, and detailed

technical documentation from the Linear Technology

website. Getting started with LTpowerPlay is easy. Simply

download and install the PC software from here:

http://www.linear.com/LTpowerPlay

WARNING:TheLTC4282 comespreprogrammedin theLow

Stress Staged Start configuration with specific settings,

which support a 200A application. Changing the LTC4282’s

programming on the DC2442 is strongly discouraged to

ensure safety and proper operation of the board. Exercise

caution if changing register settings and refer to Table 7

for key register settings, which should remain untouched.

SOFTWARE CONTROL WITH LTpowerPlay

dc2442af

DEMO MANUAL DC2442A

Figure 3. DC2442A Demo Board Connected to DC1613 I2C-to-USB Converter

Table 7. Critical Register Values for Default Demo Board Design

0x06 FET_BAD_FAULT_TIMEOUT 0 Disable FET bad timeout to ensure startup into 20,000μF. Turn on takes around 400ms

to 500ms while max FET_BAD_TIMEOUT is 255ms.

0x07 GPIO_CONFIG[5-4] 00 Power good must be enabled to ensure BYPASS channel only turns on when power is

good. This setting is essential for Low Stress Staged Start configuration

0x11 ILIM_ADJUST[7-5] 00 Current limit has been adjusted to the lowest value to minimize power dissipation in

the sense resistors. Increasing this will change the current limit as well as increase the

power dissipation in the MOSFETs.

SOFTWARE CONTROL WITH LTpowerPlay

dc2442af

DEMO MANUAL DC2442A

The DC1613 USB-to-I2C adapter interfaces the PC run-

ning LTpowerPlay to the DC2442A board. Connect the

DC1613 adapter to the PC through a USB cable, and

connect the DC2442A board through the ribbon cable

to connectorJ2 (Figure 3).

Launch the LTpowerPlay GUI on the PC. The software

identifies the DC1613 controller, then the DC2442A board,

and begins communicating through the I2C bus with the

LTC4282. Once this communication has been established,

the GUI displays its main window (Figure 4).

Figure 4. LTpowerPlay GUI Window

SOFTWARE CONTROL WITH LTpowerPlay

dc2442af

DEMO MANUAL DC2442A

The LTpowerPlay GUI divides information into separate

panes in the window. On the left is the System Tree pane,

displaying a list of all Linear Technology devices identified

on the I2C bus. For a single LTC4282 device, the tree is

small, but if other supported devices are present on the

I2C bus, LTpowerPlay will add them. Click on a device in

this list to selectively access it. Information in other panes

pertains to the selected device.

To the right of the system tree is the Configuration Reg-

ister pane displaying all of the configuration registers

available on the selected device. This view shows all of

the writable user-configurable RAM registers, and the GUI

offers clickable buttons and fields to edit the information

in these registers.

Note: Ensure that you set the resistor value of 62.5µΩ in

the Setup tab before viewing register data to get correct

current readout.

Figure 5. LTpowerPlay System Tree

Figure 6. LTpowerPlay Configuration Registers

SOFTWARE CONTROL WITH LTpowerPlay

dc2442af

DEMO MANUAL DC2442A

Figure 7. PC to RAM Button Transfers Data Programmed

from the GUI to the LTC4282 Volatile Registers

Update registers contents by clicking or typing to change

the desired registers, then selecting the “PC to RAM”but-

ton in the top toolbar. LTpowerPlay writes changes to the

updated registers.

Notethat programmingtheregisters inthe LTC4282should

generally be done while the part is in the sequenced-

down state—with the pass transistor turned off. Most of

the registers have immediate control over their respec-

tive chip functions, and changing them while the part is

sequenced-up will have unpredictable and adverse effects.

It is recommended to sequence-down before updating

configuration register settings, LTpowerPlay implements

limits to writing some registers, based upon the device

state, and will pop-up warnings when necessary.

Right of center in LTpowerPlay is the Telemetry pane,

displaying read-only information contained in the status

registers of the selected part. The GUI periodically polls

the I2C bus and updates the Telemetry contents in real

time, along with a user-friendly interpretation of the bits.

In the upper right corner of LTpowerPlay is the Chip

Dashboard pane, displaying a graphical representation of

the part status in a friendly, easy-to-understand format.

The meter in the upper left of the panel displays the static

input energy to the card in watts. The small dials in the

center of the Input Energy Meter display the energy used

in kJoules. The VSOURCE meter displays the voltage at the

SOURCE pin of the LTC4282, which is the same as VOUT.

The INPUT meter displays the voltage input at the VDD pin

of the LTC4282. VSENSE indicates the input current derived

by dividing the voltage measured across the sense resistor

divided by the value of the sense resistor. The Power Meter

displays the SOURCE voltage multiplied by the current

sense voltage and scaled to indicate the power in watts.

VGPIO3 displays the voltage at GPI03 when it is configured

as an analog input. The FET status annunciators show the

status of the pass MOSFETs as described in the FET-BAD

Fault section of the data sheets. GPI01, GPI02, and GPI03

show the status of the general purpose input/output pins.

Figure 8. LTpowerPlay Telemetry

Figure 9. LTpowerPlay Dashboard

SOFTWARE CONTROL WITH LTpowerPlay

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