Linear LTC2937 User Manual

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,

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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-

2

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

2

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

V

IN

Current to the Board Sequenced-Down 3.8 mA

I

IN

Current Sequenced-Up, No Loads 17.5 mA

I

IN

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.

†

2

C Bus Operating 10 400 kHz

0 6 V

dc2313af

1

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

2

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

2

Figure 1. DC2313A Board

dc2313af

Dc2313 operating principLes

VDD_5V

V

PWR

ON

EN1

EN6

V1

V6

SDA/SCL

. . .

LTC2937

PBB

EN

LTC2954

IN1

OUT1

IN2

OUT2

LTC4415

LED4

LED11

D1

V

OUT

V

IN

LT1761-5

V

OUT

EN

LT3008

V

OUT

EN

LT3008

LTC222

x3

LED12

LED5

LED10J3SEQUENCE

UP/DN

VIN POWER

12V

J4

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

2

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

IN

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.

2

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

2

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

dc2313af

3

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

DD

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.

4

Figure 3. DC2313A Standalone

dc2313af

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.

2

C bus. Only a bus operation can

associated LDO

and

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-

5

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)

2

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.

2

C bus. Only a bus operation can

the

fault response clears automatically.

to automatically re-sequence-up

until

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-

-

6

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).

2)

Observe the RST LED goes

LTC2937 is ignoring the UV conditions.

2

C bus operation.

-

off, indicating that the

3)

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

2

C bus in the demo

2

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

dc2313af

7

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

2

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

2

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

2

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

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

2

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.

8

dc2313af