Linear LTC2937 User Manual

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Description

DEMO MANUAL DC2313A

Programmable

Six Channel Sequencer and

Voltage Supervisor with EEPROM

Demonstration circuit 2313A showcases the LTC2937, a programmable six channel power supply sequencer and voltage supervisor.

The LTC2937 provides flexible sequence control for up to six power supplies. It enables and disables the sup plies with monitors

configurable sequence order and time delays,

the supplies for power-up and power-down time,

and for overvoltage and undervoltage. It cooperates with other LTC2937 parts in the system to coordinate power sequencing activities. It provides flexible fault response to autonomously supervise the power supplies, and powerful debug tools to diagnose any problem that causes a powersupply fault. It holds configuration in non-volatile EEPROM for completely automatic power system supervision.

The DC2313A board demonstrates the powerful features of the LTC2937 using six onboard LDO voltage regula tors, or

by controlling an optional, externally-powered

performance summary

DC1361 board (an 8-channel power supply board). Multiple DC2313A boards can also share timing and sequencing signals to supervise more than six regulated supplies in a coordinated manner.

The DC2313A connects to a PC through the DC1613 USB-

C/SMBus/PMBus Controller. This connection enables

to-I the LTpowerPlay™ software, to have complete control over the LTC2937 through the convenient LTpowerPlay GUI. The GUI allows control over all of the LTC2937 registers, and visibility into the status of the part in real time, and it works with Linear Technology demo boards as well as

custom boards with an I

C interface.

Design files for this circuit board are available at

http://www.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and LTpowerPlay is a trademark of Linear Technology Corporation. All other trademarks are the property of their respective owners.

linear.com/demo/DC2313A

PARAMETER CONDITIONS MIN TYP MAX UNITS

Voltage Range All 6 12 14 V

Current to the Board Sequenced-Down 3.8 mA

Current Sequenced-Up, No Loads 17.5 mA

V1-V6 Voltage Range Volts at the Turret 0 6 V

EN1-EN6 Voltage Range Volts at the Turret

Regulated LDO Voltage Tolerance Load Current < 20mA –1 1 %

Rated Output Current *V_OUT pins Load Current Per Channel 20 mA

Board Operating Temperature Powered 0 60 °C

Serial Clock Frequency I

†

NOTE: Analog switches U7, U8, and U9 (LTC222) are powered by 5V, and limit the maximum voltage range allowed at their S and D pins. The LTC2937

can tolerate up to 16.5V on its ENn pins.

†

C Bus Operating 10 400 kHz

0 6 V

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DEMO MANUAL DC2313A

Ltc2937 features

• Time and Event-Based Supply Sequencing

• 12Programmable Undervoltage and Overvoltage Com-

parators (0.75% Accuracy)

• Stalled

• Single

sion to 50 Devices (300 Power Supplies)

• Configuration and Fault Logging in EEPROM

• EEPROM Rated to 85°C, 10k Writes, 20 Year Retention

Power-Supply Detection

Wire Synchronization Allows Controller Expan

how to use this Document

This demonstration manual introduces the LTC2937 through a series of simple exercises using the DC2313A demo board and the LTpowerPlay software. Each exercise introduces one or two key features of the part, as well as

• Supported by LTpowerPlay GUI

• Fault and System Status Registers

• Reset Output with Programmable Delay

C/SMBus Interface

• I

• Wide Input Supply Voltage Range: 2.9V to 16.5V

• 28-Pin QFN (5mm × 6mm) Package

recommended methods for interfacing to it. The LTC2937 has more useful features than can be covered here. The user is referred to the LTC2937 data sheet, and to additional exercises in the DC2313A Advanced User Guide document.

the Dc2313a BoarD

Figure 1. DC2313A Board

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Dc2313 operating principLes

VDD_5V

PWR

EN1

EN6

SDA/SCL

. . .

LTC2937

PBB

LTC2954

IN1

OUT1

IN2

OUT2

LTC4415

LED4

LED11

OUT

LT1761-5

OUT

LT3008

OUT

LT3008

LTC222

LED12

LED5

LED10J3SEQUENCE

UP/DN

VIN POWER

12V

LDO_DISCONNECTB

LDO_VIN

3.3V_OUT

VDD_5V

LDO_VIN

I2C BUS

5V FROM USB

DC2313A F02

VDD_5V

EN1

FAULT

EN6

EN4

5V LDO

DIODE OR

...

PUSHBUTTON

CONTROL

LDO_VIN

LED13

1.2V_OUT

LED18

DEMO MANUAL DC2313A

The DC2313A board is fully functional as a stand-alone evaluation platform for the LTC2937, and does not require any external connections, other than power. It provides convenient access to all of the LTC2937 pins through turrets on the board, and basic control over the part by jumpers and pushbuttons. Connectors can attach to ex

ternal devices for system prototyping. The board has six LDO regulators that respond to control from the LTC2937, and demonstrate its capabilities.

Additional functionality is accessible using the DC1613

USB-to-I

C “dongle” and LTpowerPlay software running on a PC. The software provides a detailed view of the functions of the LTC2937, including powerful fault management and debug capabilities.

POWERING

The DC2313 can draw power from one of two sources. Either 5V from the DC1613 ribbon cable connected to J3, or from the V

connector to 12V. The DC1613 can only supply

100mA, so when the board draws power from 5V do not load any of the LDO outputs, as this may overload the 5V supply. 12V must be used when loading the LDO outputs. Multiple DC2313A boards connected together

J2 share power through the connectors, so attach 12V

and

through J1

and the ribbon cable to one of multiple DC2313A boards.

Only connect power to one of the boards. When the external DC1361 board is attached to connector J4, use 12V power.

CONFIGURATION

A key feature of the LTC2937 is its non-volatile memory (EE PROM), and its

ability to power-up in the correct configuration

to autonomously sequence and supervise the power system. The DC2313A comes pre-programmed with default settings to demonstrate the sequencing and supervision capabilities of the LTC2937. The board functions with no intervention from LTpowerPlay or other software. The pre-programmed settings on the board are not the factory default settings for the LTC2937, but are intended to provide a useful dem

onstration platform

The LTC2937 communicates through the I

with observable timing relationships.

C bus on the J3

connector. Select a bus address by changing the jumpers ASEL1, ASEL2, and ASEL3. Each jumper can select either HI, Hi-Z, or LOW, and the three jumpers together select one of 27 addresses for the device. Select a unique address

for each device on the I

C bus. If multiple DC2313 boards are connected together, each must have its own unique ASEL jumper setting. Each LTC2937 will always respond to its global 7-bit address 0x36. See the addressing section in the LTC2937 data sheet for a complete address table.

Figure 2. DC2313A Simplified Diagram

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DEMO MANUAL DC2313A

Quick start proceDure (without software)

Begin exploring the basic features of the LTC2937 with several exercises that do not require software. The following procedures DC1613 connected, and no LTpowerPlay running. The board will function autonomously without external software, which is one of the important capabilities of the LTC2937.

SEQUENCING UP

Sequence up the supplies in an orderly fashion.

1) Apply power to the DC2313A by connecting 12V to the J5 power connector.

The V

LEDs will be off.

2) Ensure that the SW3 switch is OFF, not in the MARGIN position.

3) Press the “SEQUENCE UP/DOWN” pushbutton on the DC2313.

assume a single DC2313A board with no

and RSTB LEDs will illuminate; all other

The pushbutton is de-bounced by an LTC2954, which

requires sufficient time to register the button press and activate the LTC2937 through the PB_ENB signal.

The PB_EN and GLOBAL_ON LEDs will illuminate.

The ENn LEDs will illuminate in sequence: 1-6.

The CHn LEDs will illuminate in sequence with the

ENn LEDs.

The RST LED will turn off when all supplies are within

their OV/UV limits (after the last CHn LED illuminates).

The FAULT

The ALERT LED will remain off.

The default voltage (UV and OV) limits and timing

parameters should not detect faults.

The DC2313A is programmed to provide human eye observable sequence-up timing so that the time between supplies powering-up is easily observable via LEDs. The actual LTC2937 in-system sequence of events, and the delays between events are all configurable.

LED will remain off.

Figure 3. DC2313A Standalone

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DEMO MANUAL DC2313A

Quick start proceDure (without software)

SEQUENCING DOWN

Bring down the supplies in an orderly fashion.

1) Begin with the system sequenced-up. The LDOs are on.

2) Press the “SEQUENCE UP/DOWN” pushbutton on the DC2313.

The PB_EN and GLOBAL_ON LEDs will turn off.

The ENn LEDs will turn off in sequence: 6-1.

The CHn LEDs will turn off in sequence with the ENn

LEDs.

The RST LED will illuminate as soon as the CH6 LED

goes off.

The FAULT LED will remain off.

The ALERT LED will remain off.

The default voltage (UV and OV) limits and timing

parameters should not detect faults.

Notice that the sequence-down order of events is the reverse of the sequence-up order. Channels can be reconfigured easily via register programming to sequence-up and sequence-down in any order, and sequence-down order is independent of sequence-up order. As with sequencingup, the human-friendly, eye-observable sequence timing is easily changed through register configuration.

AUTONOMOUS FAULT HANDLING

A fault is any condition that should not exist in the system. The flexible LTC2937 is capable of autonomously recognizing and handling faults without software intervention. The LTC2937 SUPERVISOR fault, SEQUENCE fault, CONTROL fault, EXTERNAL fault, and SHARE_CLK fault. We address SUPERVISOR and SEQUENCE faults here. For more in formation refer examples, do not use software, or user/external interven-

recover from the fault condition. The LTC2937 is

tion to programmed to recover on its own.

Note

that the LTC2937 ALERT pin requires a bus response to de-assert once it asserts low. When using the LTC2937 in fully autonomous mode, we ignore the ALERT pin, and

to the LTC2937 data sheet. The following

recognizes 5 types

of faults:

the ALERT LED on the board. Once it is asserted, ALERTB

will remain asserted, and the ALERT LED illuminated. This

is harmless.

Supervisor Fault

A SUPERVISOR fault is caused by overvoltage (OV) detec

tion during sequence-up, or by OV or undervoltage (UV) detection during normal operation (after a successful sequence-up). In this demo configuration the LTC2937 automatically detects the fault and re-starts all of the regulators.

Create this type of fault on the DC2313A board by pressing the FAULT pushbutton, which momentarily pulls down the EN4 line to GND, while in the sequenced-up state. This will briefly disable and bring down the create a UV condition. The LTC2937 will recognize the low

voltage and signal a SUPERVISOR fault.

1) Start with the system sequenced-up. The LDOs are on.

2) Press and release the FAULT pushbutton. This shorts EN4 to GND, disabling the 1.8V LDO.

3) Observe the fault response:

All ENn pins pull low immediately. All ENn LEDs turn

off.

All of the LDO regulated supplies turn off immediately.

All CHn LEDs turn off.

The LTC2937 is configured to automatically re-try

after the fault, so it will attempt to sequence-up the supplies. Since the fault was momentary, the resequence will succeed.

Pin FAULTB will assert low until the fault retry interval

is complete and the re-sequencing begins. The FAULT LED will illuminate during this interval.

Pin RSTB will assert low until the LDOs come-up

after re-sequencing. The RST LED will illuminate during this interval.

Pin ALERTB will assert low. The ALERT LED will

illuminate. The alert state will remain until an alert response or a read from the CLEAR_ALERTB (0x28) comes from the I release the ALERTB pin.

C bus. Only a bus operation can

associated LDO

and

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DEMO MANUAL DC2313A

Quick start proceDure (without software)

The LTC2937 monitors each channel for individuallyprogrammed overvoltage and undervoltage thresholds. The voltage monitoring is active while the supplies are up or sequencing-up.

The LTC2937 is configured to re-try after the fault; it will attempt to sequence-up again. There is a rich suite of fault response capabilities in the part, including turning off and staying off, turning-off then re-sequencing, continuing operation without turning off, or entering a debug mode. More details are available later in this manual, and in the LTC2937 data sheet.

The FAULT indicators are self-clearing upon a re-sequence initiation. The only fault indications after a successful re-sequence-up are the asserted ALERTB pin, and the EEPROM record of the first fault condition after the most recent power-up that produced the fault. The ALERTB pin will remain asserted low until the ALERT condition is cleared with an I

Sequence Fault

A SEQUENCE fault is caused by supplies failing to meet programmed voltage thresholds within programmed time allowances during sequencing (for example, not ramping fast enough).

Create this type of fault on the DC2313A board by pulling and holding down one of the ENn sequencing-up sociated LDO LTC2937 will recognize the unresponsive LDO and signal a fault.

1) Start with the system sequenced-down. The LDOs are off.

2) Short turret EN4 to GND and hold it there (press and hold the FAULT pushbutton).

3) Press the “SEQUENCE UP/DOWN” button to initiate a sequence-up operation.

EN1 - EN3 go high in sequence

CH1 - CH3 start in response to EN1-EN3

CH4 fails to start. LEDs EN4-6, CH4-6 remain off.

4) Observe the repeated fault retry response (see the table)

C bus operation.

turrets to GND while

the supplies. This will hold down the as-

and create a permanent UV condition. The

Pins EN1 - EN3 pull low immediately. All illuminated

ENn LEDs turn off.

All of the LDO regulated supplies turn off. Illuminated

CHn LEDs turn off.

The LTC2937 is conﬁgured to automatically re-try

after a delay, so it will attempt to sequence-up the supplies after detecting the fault. Since the LDO is shorted, the fault persists, and re-sequencing will repeatedly fail. The cycle will repeat until the fault is removed (by releasing the FAULT pushbutton).

Pin FAULTB will assert low for the retry interval,

re-sequence begins. LED FAULT will illuminate

the during the interval.

The FAULTB pin clears as soon as a re-sequence

begins. The FAULT LED illuminates brieﬂy, then goes off.

Pin RSTB will remain low. The RST LED will remain

illuminated because not all of the supplies ever come up.

Pin ALERTB will assert low. The ALERT LED will

illuminate. The alert state will persist until an alert response or a read from the CLEAR_ALERTB (0x28) comes from the I release the ALERTB pin.

5) Remove the EN4 fault by releasing the FAULT pushbut ton.

6) Observe that the part completes the re-sequence autonomously, and The RST LED goes off after all supplies are up.

Each channel has an independently-configurable time limit for starting-up and rising above its UV threshold voltage. Each channel also has independently-programmable sequence-down time parameters.

The LTC2937 is configured by default in the FAULT_RE SPONSE (0x23) register after all of the supplies are disabled and the voltages fall below their discharge thresholds. While the EN4 pin is held

the fault persists, and the LTC2937 is programmed

low, to automatically try to re-sequence the supplies forever, so the behavior will repeat indefinitely.

C bus. Only a bus operation can

the

fault response clears automatically.

to automatically re-sequence-up

until

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DEMO MANUAL DC2313A

Quick start proceDure (without software)

After the fault goes away the next automatic re-sequence will succeed. The FAULTB pin will de-assert. The FAULT LED will go off. Initiation of the next sequence-up operation will clear the fault information in registers. The ALERTB pin will remain asserted low until the ALERT condition is cleared with an I

Margining The Supplies

Margin testing stresses the system by moving voltages beyond their normal OV and UV limits without generating a fault. The MARGIN switch on the DC2313A board pulls down the MARGB pin on the LTC2937, causing it to ignore OV and UV faults while in the sequenced-up state. Note that the LTC2937 does not control the voltages. Margining the supplies involves pulling the regulators to out-of-spec voltages, which is done outside of the LTC2937. The LDO regulators on the DC2313A board do not change voltage, but we can demonstrate MARGIN capability while disabling one of the LDOs.

1) Begin with the system sequenced-down (all supplies OFF)

While the supplies are down, the RST LED is illumi

nated.

Switch SW3 to the MARGIN position (MARGIN active).

Observe the RST LED goes

LTC2937 is ignoring the UV conditions.

C bus operation.

off, indicating that the

Press the “SEQUENCE UP/DOWN” pushbutton to

sequence-up normally.

The PB_EN and GLOBAL_ON LEDs will illuminate.

The ENn LEDs will illuminate in sequence: 1-6.

The CHn LEDs will illuminate in sequence with the

ENn LEDs.

The RST LED will remain off because the MARGIN

function is active.

The FAULT LED will remain off.

The ALERT LED will remain off.

No voltage (UV and OV) limits are measured. The

default timing parameters should not detect faults.

4) While the MARGIN switch is active, short the EN4 turret to GND by pressing the FAULT pushbutton.

The corresponding CH4 will go down and the LED

will go off.

No faults are detected due to the MARGIN function.

Note that the MARGIN function is only useful while the supplies are sequenced-up, not while they are in the process of sequencing. Holding the MARGB pin asserted low does not mask SEQUENCE (timing) faults during sequencingup operations. If a supply fails to meet its programmed sequence-up voltage/timing requirements then the normal fault response prevails, regardless of MARGB state.

software controL with LtpowerpLay

LTpowerPlay is a convenient PC complete 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 LTpowerPlay communicates using the I system (covered in this manual), or in your real-world product environment. It provides unprecedented control over the Linear Technology chips on the I

access to the registers of the LTC2937, and many

to configure and debug your application.

software GUI that gives

C bus in the demo

C 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. On-line help includes quick-start videos and tutorials, and detailed technical documentation from the Linear Technology web site. Getting started with LTpowerPlay is easy. Simply download and install the PC software from here:

http://www.linear.com/ltpowerplay

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DEMO MANUAL DC2313A

software controL with LtpowerpLay

To the right of the system tree is the Configuration Register pane, displaying all of the configuration registers available on writable offers clickable buttons and fields to edit the information in these registers.

the selected device. This view shows all of the

LTpowerPlay System Tree

user-configurable RAM registers, and the GUI

Figure 4. DC2313A Demo Board Connected to DC1613A I2C-to-USB Converter

The DC1613 USB-to-I2C adapter interfaces the PC running LTpowerPlay to the DC2313A board (or any board with an

C bus). Connect the DC1613 adapter to the PC through a

I USB cable, and connect it to the DC2313A board through the ribbon cable to connector J3.

Launch the LTpowerPlay GUI on the PC. The software identifies the DC1613 controller, then the DC2313A board, and begins communicating through the I LTC2937. Once this communication has been established, the GUI displays its main window (Figure 5).

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 I small, but if other supported devices are present on the

I this list to selectively access it. Information in other panes pertains to the selected device.

C bus. For a single LTC2937 device, the tree is

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

C bus with the

LTpowerPlay Configuration Registers

Update register contents by clicking or typing to change the desired registers, then selecting the “Write All” but-

the top toolbar. LTpowerPlay writes changes to the

ton in updated registers.

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DEMO MANUAL DC2313A

software controL with LtpowerpLay

Figure 5. LTpowerPlay GUI Window

Note that programming the registers in the LTC2937 should generally be done while the part is in the sequenced-down state. Most of the registers have immediate control over their respective chip functions, and changing them while the part is sequenced-up will have unpredictable and ad

. It is

verse effects 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

C bus and updates the Telemetry contents in real

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

recommended to sequence-down before

LTpowerPlay Telemetry

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DEMO MANUAL DC2313A

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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 live channel voltage comparator OV and UV states are shown in the “Comparator Status”. The sequencing state is represented in the “Sequencing” block. Fault status is summarized in the “Fault Summary” block. Other status bits are represented by light-up red-yellow-green indica tors on the part status at-a-glance.

the right-hand side. These intuitive indicators give

LTpowerPlay Chip Dashboard

The LTC2937 features an EEPROM non-volatile memory

that holds device configuration information and a snapshot of past fault information. When the part receives power it executes a power-on reset, and restores the contents of the EEPROM to its operating RAM memory. Following this power-on restore, operating RAM memory can be modified with I

behavior. This modified state can be stored to the EEPROM

with a STORE (0x2C) command, making it available as the

future default power-up state. The STORE command will

copy the entire contents of the configuration RAM into

EEPROM. The data sheet recommends storing EEPROM

contents only while the part is sequenced-down.

In addition to power-on reset, the EEPROM contents can

also be retrieved to RAM operating memory with a RE

STORE (0x2D) command. RESTORE wipes-out the content

of the RAM and replaces it with the EEPROM contents.

Only perform a RESTORE when the LTC2937 is in the

sequenced-down state, as the RAM operating memory

immediately affects the chip, and changing its contents

while sequenced-up can result in unpredictable behavior.

C bus commands that modify the part

LTC2937 REGISTERS

LTC2937 RAM and Non-Volatile Memory

The LTC2937 is highly configurable through its register set. Refer to the LTC2937 data sheet for a complete discussion of the registers and functions available. Get immediate access to detailed help for the selected register in LTpowerPlay by pressing the F1 key on your keyboard.

Both RAM and EEPROM respect write-protection on the

LTC2937. Both the

(0x00) register provide write protection. Configure both the

pin and the register to allow writing to memory. To enable

writing, pull the hardware WP pin to ground by setting

jumper JP4 to DIS. Write the command 0x00 with bit 0 = 0,

and the same key that is in WRITE_PROTECTION[15:2]. The

demo board default for the WRITE_PROTECTION register

and the WP pin allow writing to memory.

The following exercises approach the registers in a task-

oriented manner, demonstrating register functions through

examples.

Default Configuration

If the LTC2937 EEPROM contains non-default contents,

then returning it to the demo-board default settings can

be accomplished with the LTpowerPlay “Demo” menu

selection.

WP pin and the WRITE_PROTECTION

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Clicking the “Demoboard Defaults” menu item stores default register settings in RAM, issues a CLEAR command, then contents into its default setting for the demo board. Note that this procedure only works if the ASEL jumpers are configured in their default settings:

ASEL1 = HI

ASEL2 = HI

ASEL3 = HI

ON/OFF CONTROL

The LTC2937 provides control over all of its functions through the register interface. This includes ON/OFF con trol. The to

a register ON/OFF bit, or to both. In this exercise, we will sequence the system up and down using the I command, ignoring the hardware ON/OFF pin. To program the part to turn on and off through the I

executes a STORE command to store the RAM

into EEPROM. This places the LTC2937 back

part can respond to the hardware ON/OFF pin, or

C bus

C bus:

The supplies sequence-up normally

The ENn LEDs will illuminate in sequence: 1-6.

The CHn LEDs will illuminate in sequence with the

ENn LEDs.

The RST LED will turn off after the last CHn LED

illuminates.

The LTC2937 Chip Dashboard in LTpowerPlay

tracks the internal register status in real time as it sequences-up.

1) Start with the part sequenced-down (PB_EN LED is off,

LDOs are off).

2) Program register ON_OFF_CONTROL (0x02) by clicking

the checkboxes for each bit to sequence-up via the I bus:

b[2] = 0 (ignore the ON input pin)

b[3] = 1 (honor the software ON/OFF bit)

b[4] = 1 (software ON

3) Send the register updates from LTpowerPlay to the

LTC2937 by pressing the Write All Button:

/OFF state is ON)

In the LTC2937 internal registers:

The ON_OFF_CONTROL[7] bit becomes set, indicat

ing that the part is commanded to sequence-up.

The STATUS_INFORMATION[11:10] bits cycle

through the sequence-up states:

00b : sequence-down complete

01b : sequence-up in-progress

11b : sequence-up complete

The SEQ_POSITION_COUNT[9:0] bits count through

the sequence-up states (1 – 7).

The FAULT LED will remain off.

The ALERT LED will remain off.

The PB_EN and GLOBAL_ON LEDs will remain off.

The ON pin is low.

The default voltage (UV and OV) limits and timing

parameters should not detect faults.

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5) Setting register bit ON_OFF_CONTROL[4] = 0

commands the part to sequence-down. All sequence timing and voltage limits apply. Click the i2c_on_off (b[4]) checkbox and hit ‘F12’ on the keyboard to update the register in the LTC2937.

The ENn LEDs will turn off in sequence: 6-1.

The CHn LEDs will turn off in sequence with the ENn

LEDs.

The RST LED will illuminate after the ﬁrst CH6 LED

turns off.

The ON_OFF_CONTROL[7] bit becomes low, indicating

that the part is commanded to sequence-down.

Restore the EEPROM default register settings by execut ing a RESTORE (0x2D) command. In LTpowerPlay this

command

followed by the read RAM registers button:

SUPPLY SEQUENCE ORDER

The LTC2937 provides complete sequence order and timing control over enabling and disabling supplies to go down in any (different) order. The LTC2937 provides up to 1023 ordered sequence positions in which events can be scheduled during sequence-up and sequence-down. Each supply has its own SEQ_UP_POSITION_n register (0x16 – 0x1B) and SEQ_DOWN_POSITION_n register (0x1C – 0x21). In the demo-board default settings, the supplies sequence-up in the order 1-6, and sequencedown in the order 6-1. We can change this ordering by writing to the registers:

is issued by pressing the RESTORE button,

the supplies. Sequenced

can be commanded to come-up in any order, and

The STATUS_INFORMATION[11:10] bits cycle through

the sequence-down states:

11b : sequence-up complete

10b : sequence-down in-progress

00b : sequence-down complete

The SEQ_POSITION_COUNT[9:0] bits count through

the sequence-down states (1 – 7).

The FAULT LED will remain off.

The ALERT LED will remain off.

The PB_EN and GLOBAL_ON LEDs will remain off. The

ON pin is low.

The default voltage (UV and OV) limits and timing

parameters should not detect faults.

This procedure is equivalent to pressing the “SEQUENCE UP/DOWN” pushbutton on the board to command a sequence-up and sequence-down.

1) Begin with the LTC2937 in the sequenced-down state (all supplies off).

2) Write each of the 6 SEQ_UP_POSITION_n registers to change their sequence positions:

SEQ_UP_POSITION_1 = 0x0005 : place channel 1 in

sequence position 5

Do this by clicking on the “SEQ_UP_POSITION_1_

LT C2937” text, and typing 0x0805 then ENTER. This updates the register value in the GUI.

You may also click on “seq_up_position (b[9:0])” and

typing “5” ENTER. Notice that the hex value updates as a result.

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4) If you have not already written the GUI conﬁguration to RAM (using F12), then update all registers with the Write All button

5) Initiate a sequence-up by writing ON_OFF_CONTROL[4:2] = 110.

After modifying a register hit F12 on the keyboard to

update that register in the LTC2937 RAM.

Continue with the other channels:

SEQ_UP_POSITION_2 = 0x0007 : place channel 2 in

sequence position 7

SEQ_UP_POSITION_3 = 0x0003 : place channel 3 in

sequence position 3

SEQ_UP_POSITION_4 = 0x0001 : place channel 4 in

sequence position 1

SEQ_UP_POSITION_5 = 0x0002 : place channel 5 in

sequence position 2

SEQ_UP_POSITION_6 = 0x0004 : place channel 6 in

sequence position 4

3) Write each of the 6 SEQUENCE_DOWN_POSITION_n registers to change their sequence positions:

SEQ_DOWN_POSITION_1 = 0x0001 : place channel 1

in sequence position 1

SEQ_DOWN_POSITION_2 = 0x0001 : place channel 2

in sequence position 1

SEQ_DOWN_POSITION_3 = 0x0007 : place channel 3

in sequence position 7

SEQ_DOWN_POSITION_4 = 0x0003 : place channel 4

in sequence position 3

Remember that we are programmed to ignore the

SEQUENCE UP/DOWN pushbutton.

6) Observe the modiﬁed sequence-up order as the sup plies come up.

The ON_OFF_CONTROL[7] bit becomes set

The STATUS_INFORMATION[11:10] bits cycle

through the sequence-up states

The SEQ_POSITION_COUNT[9:0] bits count through

the sequence-up states (1-8).

7) Initiate a sequence-down by writing ON_OFF_CON TROL[4:2] = 010.

The SEQ_POSITION_COUNT[9:0] bits count through

the sequence-down states (1-1023-0).

Notice that channel 5 is in the last sequence-down

position (1023). During sequence-down operation the SEQUENCE POSITION COUNT will count up to 1023 before de-activating EN5, then roll-over to count 0 before stopping.

Restore the EEPROM default register settings by

executing a RESTORE (0x2D) command. In LT powerPlay this RESTORE button, followed by the read RAM registers button:

command is issued by pressing the

SEQ_DOWN_POSITION_5 = 0x03FF : place channel 5

in sequence position 1023

SEQ_DOWN_POSITION_6 = 0x0004 : place channel 6

in sequence position 4

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Each supply can occupy any one of the 1023 available sequence positions. Multiple supplies can occupy the same sequence position – for example, they could all occupy sequence position 3. Unused sequence positions take a minimal amount of time (80µs) to complete, but do not trigger any enable or disable events. The part continues counting until the last used sequence position, plus one.

Within each sequence position, additional flexibility is available for enable and disable timing of each supply using the ton_delay and toff_delay settings. Each supply can delay up to 655ms from the start of its sequence position before enabling (TON_TIMERS[12:0]) or disabling (TOFF_TIMERS[12:0]). This provides deterministic timing relationships between supplies within a sequence position. The sequence position clock waits for all scheduled sup plies in that position. These behaviors are best observed with a scope, since the time resolution is microseconds – much faster than the eye can observe the LEDs on the board sequencing.

Further flexibility is available if multiple LTC2937s sequence many supplies. The LTC2937 parts communicate through the SPCLK and SHARE_CLK signals so that they maintain a common sequence count and timebase, and a large number of supplies autonomously SEQ_UP_POSITION, SEQ_DOWN_POSTION, ton_delay, and toff_delay registers to freely interleave supplies across multiple LTC2937s.

coordinated, deterministic manner. Use the

can be sequenced in an

Try Count

Re-

In the DC2313 demo board the LTC2937 is configured

to re-try an unlimited number of times when it detects a SUPERVISOR or SEQUENCE fault. It can instead be configured to respond in a limited way to a fault, and give-up if the problem persists. The number of re-try attempts can be set with the FAULT_RESPONSE[2:0] register bits (retry_number). Any number of attempts can be specified, from 0 to 6, or unlimited. The to a SUPERVISOR or SEQUENCE fault by turning-off the

supplies, then trying to sequence-up. It will register the

number of attempts in the FAULT_RESPONSE[13:11] bits, and stay off after failing the specified number of times.

Fault Debug

In this exercise set the fault response to zero automatic re-tries, which will enable debugging. Create a fault on the DC2313A board with the FAULT pushbutton.

1) Start with the system sequenced-down. The LDOs are off.

2) Set FAULT_RESPONSE[2:0] = 0x0. This sets zero re-try attempts after a fault.

part will

respond

FAULT RESPONSE

To this point, the demonstrations have shown the LTC2937 responding to faults by autonomously re-starting the supplies without software. This important behavior is only one of the possible choices, however. The LTC2937 provides a rich and configurable set of fault response capabilities allowing either an autonomous recovery, an

C bus mediated response, or a completely interactive

I software debugging experience.

The LTC2937 data sheet details all of the fault-response registers, and the various programming options for han dling faults, and debugging behaviors. Below are several examples.

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3) Press the “SEQUENCE UP/DOWN” pushbutton and wait for sequence-up to complete.

4) Press and release the FAULT pushbutton, momentarily shorting EN4 to GND and bringing down the 1.8V LDO. The LTC2937 immediately recognizes the low V4 voltage.

5) Observe the fault response

All ENn pins pull low immediately. All ENn LEDs turn off.

All of the LDO regulated supplies turn off immediately. All Chn LEDs turn off.

The fault response setting allows no re-try attempts, so the supplies remain off.

Pin FAULTB will assert and remain low. LED FAULT will illuminate.

Pin RSTB will assert low. LED RST will illuminate.

Pin ALERTB will assert low. LED ALERT will illuminate. The alert state will remain until an alert response or a read from the CLEAR_ALERTB (0x28) comes from

C bus.

the I

Register MONITOR_STATUS (0x30) will briefly report the real time UV comparator assertion until the fault goes away when the FAULT button is released.

Register MONITOR_STATUS_HISTORY (0x26) will report the latched SUPERVISOR UV fault condition. This information remains because the LTC2937 does not re-sequence.

The LTpowerPlay Chip Dashboard shows the summary of fault information. This conveniently indicates that the part has detected a SUPERVISOR UV fault, and that fault information is stored in the EEPROM MONITOR_BACKUP register.

Note that the V4 dial has a double red arc, indicating that the V4 channel caused the UV fault that brought-down the system.

Notice that ALL status information is retained in the state it was in when the fault occurred. This includes the sequencer state (SP=7, Syst=UP, Chip=UP). The STATUS_ INFORMATION[11:10] and STATUS_INFORMATION[9:8] were in the “sequence-up complete” state when the fault occurred, so these states are retained. The state machine still thinks it is in the same state.

Register MONITOR MONITOR_STATUS_HISTORY register contents, but only if this is the first fault since power applied. If this is not the first fault, MONITOR_BACKUP will contain older fault information. Execute a RESTORE command to view the MONITOR_BACKUP register contents.

The LTC2937 does not attempt to recover from the fault. Instead, it turns-off all of the supplies and retains all of its status register contents. This enables a thorough postfault examination of status registers in the state they were when the fault occurred.

_BACKUP in

EEPROM will mirror

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DEMO MANUAL DC2313A

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Status register contents are cleared when the LTC2937 begins a new sequence-up operation, so allowing auto-

-try

matic re that might exist in the registers.

The only fault information that will persist beyond a successful re-sequence initiation is in the EEPROM MONITOR_BACKUP register, which stores the contents of the MONITOR_STATUS_HISTORY register when the first fault after power-up is detected.

The ALERTB pin will remain asserted low until the ALERT condition is cleared with an I

Recovering from and Clearing Faults

The FAULTB pin and status registers respond to a fault condition, but can be cleared when the LTC2937 resequences the power supplies. Along with the status information registers, the FAULTB pin is cleared when the sequence starts. In the case where fault information and the FAULTB pin need to be cleared manually, the CLEAR (0x2E) command is available.

after a fault eliminates the debug information

C bus (ARA) operation.

Clearing the ALERTB Pin

The ALERTB pin conforms to the SMBus protocol for the SMBALERT fault response. It is designed to act as an interrupt for a controller on the I ALERTB pin asserts when a fault event occurs, and it can

only be cleared by an appropriate bus response from the

controller.

When the ALERTB pin asserts, a controller may either execute an alert response through the Alert Response Address (0x0C), which is a defined as the ARA in the SMBus protocol, or the controller may read from register CLEAR_ALERTB (0x28) to immediately de-activate the ALERTB pin.

LTpowerPlay will include the CLEAR_ALERTB command when sending a CLEAR_FAULTS command if the behavior is selected in the Preferences menu. Pull-down View→ Preferences…, then select “Issue CLEAR_ALERTB on CLEAR” = TRUE. When you click the CLEAR_FAULTS button in the GUI it will also clear ALERTB.

C bus. The LTC2937

LTpowerPlay allows the user to issue the CLEAR command (0x2E) that clears the fault and status registers. Issue the CLEAR command by pressing the “CLEAR” button in the toolbar:

Warning: avoid issuing a CLEAR command while the LTC2937 is in the sequenced-up state. The registers and state-machines that get cleared have an immediate ef fect on the part, and will cause the supplies to fault and re-sequence, which is usually an undesired behavior. Sequence-down before issuing a CLEAR command.

If the LTC2937 is waiting, not re-trying, after a fault, turn it off (press the “SEQUENCE UP/DOWN” button to turnoff the PB_EN and GLOBAL_ON LEDs). The LTC2937 will retain state, but will be ready to sequence-up. Press the “SEQUENCE UP/DOWN” button again to sequence-up normally and clear the latched fault status and the FAULTB pin. The ALERT pin will remain asserted until cleared.

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DEMO MANUAL DC2313A

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EEPROM Fault Backup

The LTC2937 stores information about the “first” fault that it detects into the EEPROM MONITOR_BACKUP register. The information is a copy of the MONITOR_STATUS_HISTORY register at the time of the fault. Subsequent power-cycling has no effect on this stored information, which can be read with the MONITOR_BACKUP command (0x2F) after a RESTORE, or a after a power-cycle. This debug information survives subsequent sequencing operations, and power cycling. Only the first fault information is stored in EEPROM. The indicator bit, STATUS_INFORMATION[12] holds a persistent 1 if the MONITOR_BACKUP register contains a fault record.

Re-arm the MONITOR_BACKUP register to accept a new “first” fault by clearing it according to this recipe:

1) Begin in the sequenced-down state. The supplies are off. The register STATUS_INFORMATION[11:8] = 0x0.

2) Issue a CLEAR command (0x2E) by pressing the “CF” button in LTpowerPlay. This clears any fault information, including MONITOR_STATUS_HISTORY.

4) Issue a RESTORE command (0x2D). This restores the clean MONITOR_BACKUP register contents from EEPROM. It clears the STATUS_INFORMATION[12] indicator bit. It also restores all conﬁguration registers from EEPROM.

Note that it is important to perform the CLEAR and RE

(

STORE operations sequencing-down. The internal sequencing state machine receives a reset when the CLEAR command is issued. If the LTC2937 is sequenced-up, or in the process of sequenc ing, this reset will generate a fault, possibly turn off the supplies, and re-sequence-up.

be aware that the STORE command affects the entire

Also EEPROM, not only the MONITOR_STATUS_HISTORY word. This means that any changes that have been made to the RAM configuration registers will be stored in EEPROM. Also, if there is newer fault information in RAM than in the first fault MONITOR_BACKUP register, it will be stored into EEPROM with a STORE command.

in that order) while the part is finished

3) Issue a STORE command (0x2C). This stores the clean MONITOR_STATUS_HISTORY register contents to EEPROM. It also stores all conﬁguration registers to EEPROM.

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DEMO MANUAL DC2313A

Dc2313a BoarD Description

Figure 6. DC2313A Demo Board Layout

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DEMO MANUAL DC2313A

parts List

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

Required Circuit Components

1 4 C1, C7, C10, C17 CAP., 0.1µF, X5R, 16V, 10%, 0603 MURATA, GRM188R61C104KA01D

2 7 C2, C11-C16 CAP., 2.2µF, X5R, 10V, 10%, 0603 MURATA, GRM188R61A225KE34D

3 2 C3, C4 CAP., 0.01µF, X7R, 10V, 10%, 0603 AVX, 0603ZC103K AT2A

4 2 C5, C9 CAP., 10µF, X5R, 16V, 10%, 0805 MURATA, GRM21BR61C106KE15L

5 1 C6 CAP., 22µF, X5R, 25V, 20%, 0805 MURATA, GRM21BR61E226ME44K

6 1 C8 CAP., 1µF, X5R, 16V, 10%, 0603 MURATA, GRM188R61C105KA93D

7 1 D1 DIODE, Schottky, SOT23 VISHAY, BAS70-05-E3-08

8 34 E1-E34 TEST POINT, TURRET, .094" MTG. HOLE MILL-MAX, 2501-2-00-80-00-00-07-0

9 3 JP1, JP2, JP3

10 2 JP4, JP5

11 1 J1

12 1 J2

13 1 J3

14 1 J4

15 1 J5 CONN., POWER JACK, 2.1mm CUI INC., PJ-002AH

16 0 J6

17 2 LED1, LED3 LED, RED, 0603 PANASONIC, LNJ237W82RA

18 1 LED2 LED, AMBER, 0603 PANASONIC, LNJ426W83RA

19 15 LED4-LED18 LED

21 6 Q8-Q13 XSTR., NPN, SOT23 FAIRCHILD, MMBT3904

22 19 R1-R4, R6, R8, R10,

23 20 R5, R7, R9, R11, R13,

24 1 R20 RES., 374k, 1/16W, 1%, 0402 VISHAY, CRCW0402374KFKED

25 11 R27, R28, R32, R37,

26 1 R31 RES., 46.4k, 1/16W, 1%, 0402 VISHAY, CRCW040246K4FKED

27 1 R33 RES., 9.31k, 1/16W, 1%, 0402 VISHAY, CRCW04029K31FKED

28 1 R34 RES., 249, 1/16W, 1%, 0402 VISHAY, CRCW0402249RFKED

29 1 R35 RES., 1k, 1/16W, 1%, 0402 VISHAY, CRCW04021K00FKED

30 6 R43, R44, R50,

31 1 R49 RES., 1.37M, 1/16W, 1%, 0402 VISHAY, CRCW04021M37FKED

32 1 R51 RES., 590k, 1/16W, 1%, 0402 VISHAY, CRCW0402590KFKED

33 1 SW1 SWITCH, Push Button, SW-PTS635-25 C&K Components, PTS635SK25SMTR LFS

7 Q1-Q7 XSTR., MOSFET, N-CH, SOT523 DIODES INC., DMG1012T-7

R12, R14, R16, R18, R23, R29, R39, R40, R45, R46, R53, R54

R15, R17, R19, R21, R22, R24-R26, R30, R59-R64

R38, R41, R42, R47, R48, R55, R56

R52, R57, R58

CONN., HEADER, 1×4, 2mm

CONN., HEADER, 1×3, 2mm

CONN., HEADER, 2×10, .100", R/A

CONN., SOCKET, 2×10, .100", R/A

CONN., HEADER, 2×6, 2mm, STR DL PCB

CONN., SOCKET, 2×27, .100", R/A

, GREEN, 0603 PANASONIC, LNJ326W83RA

RES., 3.01k, 1/10W, 1%, 0402 VISHAY, CRCW04023K01FKED

RES., 100k, 1/16W, 1%, 0402 VISHAY, CRCW0402100KFKED

RES., 10k, 1/16W, 1%, 0402 VISHAY, CRCW040210K0FKED

RES., 200k, 1/16W, 1%, 0402 VISHAY, CRCW0402200KFKED

SULLINS, NRPN041PAEN-RC

SULLINS, NRPN031PAEN-RC

MILL-MAX, 802-40-020-20-001000

MILL-MAX, 803-93-020-20-001000

FCI, 98414-G06-12ULF

SULLINS, PPTC272LJBN-RC

OPT

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DEMO MANUAL DC2313A

parts List

ITEM QTY REFERENCE PART DESCRIPTION MANUFACTURER/PART NUMBER

34 1 SW2 SWITCH, Push Button, SW-PTS635-25 C&K Components, PTS635SL25SMTR LFS

35 1 SW3 CONN, SUB MINIATURE SLIDE SWITCHES C&K.,JS202011CQN

36 1 U1

37 2 U2, U3 I.C., DUAL BUFFERS, TSOP-6 NXP, 74LVC 2G07GV,125

38 1 U4

39 1 U5 I.C., LINEAR REG - 5V, TSOT23-5 LINEAR TECH., LT1761ES5-5

40 1 U6 I.C., DIODE OR, MSE16 LINEAR TECH., LTC4415IMSE

41 3 U7, U8, U9 I.C ANALOG SWITCH, SO16 LINEAR TECH, LTC222CS

42 1 U10 I.C SERIAL EEPROM, TSSOP8 MICROCHIP, 24AA02-I /ST

43 1 U11

44 1 U12

45 1 U13

46 1 U14

47 1 U15

48 1 U16

49 5 SHUNTS ON JP1-JP5

PINS 1&2

50 4 MH1-MH4 ST

I.C, LTC2937IUHE, QFN28UHE-5×6

I.C., PUSH BUTTON, DFN8DDB-3×2

I.C, LINEAR REG., DFN6DC-2×2

SHUNT, .079" CENTER SAMTEC, 2SN-BK-

ANDOFF, SNAP ON, 1/4" KEYSTONE, 8831

LINEAR TECH., LTC2937IUHE

LINEAR TECH., LTC2954IDDB-2

LINEAR TECH., LT3008IDC-3.3

LINEAR TECH., LT3008IDC-2.5

LINEAR TECH., LT3008IDC

LINEAR TECH., LT3008IDC-1.8

LINEAR TECH., LT3008IDC-1.5

LINEAR TECH., LT3008IDC-1.2

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schematic Diagram

DEMO MANUAL DC2313A

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DEMO MANUAL DC2313A

schematic Diagram

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schematic Diagram

DEMO MANUAL DC2313A

Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.

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DEMO MANUAL DC2313A

DEMONSTRATION BOARD IMPORTANT NOTICE

Linear Technology Corporation (LT C) provides the enclosed product(s) under the following AS IS conditions:

This demonstration board (DEMO BOARD) kit being sold or provided by Linear Technology is intended for use for ENGINEERING DEVELOPMENT OR EVALUATION PURPOSES ONLY and is not provided by LT C for commercial use. As such, the DEMO BOARD herein may not be complete in terms of required design-, marketing-, and/or manufacturing-related protective considerations, including but not limited to product safety measures typically found in finished commercial goods. As a prototype, this product does not fall within the scope of the European Union directive on electromagnetic compatibility and therefore may or may not meet the technical requirements of the directive, or other regulations.

If this evaluation kit does not meet the specifications recited in the DEMO BOARD manual the kit may be returned within 30 days from the date of delivery for a full refund. THE FOREGOING WARRANTY IS THE EXCLUSIVE WARRANTY MADE BY THE SELLER TO BUYER AND IS IN LIEU OF ALL OTHER WARRANTIES, EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING ANY WARRANTY OF MERCHANTABILITY OR FITNESS FOR ANY PARTICULAR PURPOSE. EXCEPT TO THE EXTENT OF THIS INDEMNITY, NEITHER PARTY SHALL BE LIABLE TO THE OTHER FOR ANY INDIRECT, SPECIAL, INCIDENTAL, OR CONSEQUENTIAL DAMAGES.

The user assumes all responsibility and liability for proper and safe handling of the goods. Further, the user releases LT C from all claims arising from the handling or use of the goods. Due to the open construction of the product, it is the user’s responsibility to take any and all appropriate precautions with regard to electrostatic discharge. Also be aware that the products herein may not be regulatory compliant or agency certified (FCC, UL, CE, etc.).

No License is granted under any patent right or other intellectual property whatsoever. LTC assumes no liability for applications assistance,

customer product design, software performance, or infringement of patents or any other intellectual property rights of any kind.

LT C currently services a variety of customers for products around the world, and therefore this transaction is not exclusive.

Please read the DEMO BOARD manual prior to handling the product. Persons handling this product must have electronics training and

observe good laboratory practice standards. Common sense is encouraged.

This notice contains important safety information about temperatures and voltages. For further safety concerns, please contact a LTC application engineer.

Mailing Address:

Linear Technology

1630 McCarthy Blvd.

Milpitas, CA 95035

Linear Technology Corporation

1630 McCarthy Blvd., Milpitas, CA 95035-7417

(408) 432-1900 ● FAX: (408) 434-0507 ● www.linear.com

dc2313af

LT 0615 • PRINTED IN USA

 LINEAR TECHNOLOGY CORPORATION 2015