Linear LTC2937 User manual

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dc2313af
DEMO MANUAL DC2313A
Description
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 configurable sequence order and time delays,
monitorsthe suppliesfor power-up and power-downtime,
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
autonomouslysupervisethepower supplies, and powerful
debug tools to diagnose any problem that causes a power-
supplyfault.Itholdsconfigurationinnon-volatileEEPROM
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
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.
performance summary
DC1361board(an8-channelpower 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-
to-I2C/SMBus/PMBus Controller. This connection enables
the LTpowerPlay™ software, to have completecontrol 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 I2C interface.
Design files for this circuit board are available at
http://www.linear.com/demo/DC2313A
PARAMETER CONDITIONS MIN TYP MAX UNITS
VIN Voltage Range All 6 12 14 V
IIN Current to the Board Sequenced-Down 3.8 mA
IIN 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†0 6 V
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 I2C Bus Operating 10 400 kHz
†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.

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DEMO MANUAL DC2313A
Ltc2937 features
how to use this Document
the Dc2313a BoarD
Figure 1. DC2313A Board
• Time and Event-Based Supply Sequencing
• 12Programmable Undervoltage and Overvoltage Com-
parators (0.75% Accuracy)
• Stalled Power-Supply Detection
• Single Wire Synchronization Allows Controller Expan-
sion to 50 Devices (300 Power Supplies)
• Configuration and Fault Logging in EEPROM
• EEPROM Rated to 85°C, 10k Writes, 20 Year Retention
• Supported by LTpowerPlay GUI
• Fault and System Status Registers
• Reset Output with Programmable Delay
• I2C/SMBus Interface
• Wide Input Supply Voltage Range: 2.9V to 16.5V
• 28-Pin QFN (5mm ×6mm) Package
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
recommended methods for interfacing to it. The LTC2937
has more useful features than can be covered here. The
userisreferred tothe LTC2937 data sheet, and to additional
exercisesin the DC2313AAdvancedUserGuidedocument.

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DEMO MANUAL DC2313A
Dc2313 operating principLes
Figure 2. DC2313A Simplified Diagram
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-I2C“dongle” and LTpowerPlay software running on
aPC. The software provides adetailed 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 VIN 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 through J1
and J2 share power through the connectors, so attach 12V
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),anditsabilitytopower-upinthecorrectconfiguration
toautonomouslysequenceandsupervisethepowersystem.
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, with observable timing relationships.
The LTC2937 communicates through the I2C 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 I2C 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.
VDD_5V
VPWR
ON
EN1
EN6
V1
V6
SDA/SCL
. . .
LTC2937
PBB
EN
LTC2954
IN1
OUT1
IN2
OUT2
LTC4415
LED4
LED11
D1
VOUT
VIN
LT1761-5
VOUT
EN
LT3008
VOUT
EN
LT3008
LTC222
. . .
x3
LED12
LED5
LED10
J3
SEQUENCE
UP/DN
VIN POWER
12V
J4
LDO_DISCONNECTB
LDO_VIN
3.3V_OUT
VDD_5V
LDO_VIN
PB_EN
GLOBAL_ON
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

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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 follow-
ing procedures assume a single DC2313A board with no
DC1613connected, andnoLTpowerPlay running. Theboard
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 VDD and RSTB LEDs will illuminate; all other
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.
Thepushbutton is de-bounced byanLTC2954, which
requires sufficient time to register the button press
andactivatetheLTC2937throughthePB_ENBsignal.
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
theirOV/UV limits(afterthe lastCHnLED illuminates).
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.
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.
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.
Noticethat thesequence-downorderof eventsis thereverse
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 sequencing-
up, 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 recognizes 5 types of faults:
SUPERVISOR fault, SEQUENCE fault, CONTROL fault,
EXTERNAL fault, and SHARE_CLK fault. We address
SUPERVISOR and SEQUENCE faults here. For more in-
formation refer to the LTC2937 data sheet. The following
examples, do not use software, or user/external interven-
tion to recover from the fault condition. The LTC2937 is
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
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 associated LDO and
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.
AlloftheLDO regulated supplies turnoffimmediately.
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 re-
sequence will succeed.
Pin FAULTB will assert low until the fault retry interval
iscomplete andthe 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 I2C bus. Only a bus operation can
release the ALERTB pin.