Use LTpowerPlay to configure and debug an LTC2937, plan distinct I²C addresses before adding devices, and provide an explicit control signal if you need rails to shut down in sequence. A supervisor fault alone turns the enable outputs off together; it does not create a timed down-sequence. This guide covers the software workflow, mixed-voltage bus connections, controlled shutdown, and linking sequencers for more than six supply rails.
Configure and debug the LTC2937 with LTpowerPlay
LTpowerPlay is the primary interface for setting up and inspecting the LTC2937. It can program device registers and nonvolatile EEPROM, save and restore configuration projects, display status and telemetry in real time, visualize sequencing, help diagnose faults, and let you step through power-up or power-down sequences one step at a time. These capabilities make it useful both when building a configuration and when checking why a rail did not behave as expected.
- Configure: Set the sequencing and supervision behavior in LTpowerPlay, then program the operating registers or store the settings in EEPROM for autonomous startup.
- Validate: Use the sequencing view and single-step controls to inspect the order of transitions without relying only on a full system startup.
- Debug: Review live status and telemetry alongside fault information to identify which monitored condition or transition needs attention.
- Preserve: Save a project so the configuration can be restored or reviewed later.
Programming EEPROM supports operation without a continuously connected computer, but stored configuration does not itself supply a shutdown command when input power starts to disappear. Choose an ON-pin or bus-master control path if an orderly shutdown is required.
Plan I²C addresses before adding sequencers
The LTC2937 ASEL pins select one of 27 seven-bit addresses. In a design with multiple devices, assign each LTC2937 a different selected address so the bus master can address them individually. Each device also responds to the global seven-bit address 0x36 and the SMBus Alert Response Address 0x0C; do not treat those shared response addresses as unique device addresses.
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For multiple sequencers, verify the chosen ASEL settings across the whole system before connecting the bus. The individual slave addresses must remain unique even when the devices share sequencing and fault signals.
Bridge incompatible or independently powered I²C segments
Use a bus buffer when the bus master and LTC2937 operate in different voltage domains, or when one segment can be unpowered while another remains active. The design guide identifies the LTC4313 for connecting a 2.5 V or 1.8 V bus master to the LTC2937’s 3.3 V domain, and for isolating an unpowered segment that could otherwise pull SCL or SDA low.
A buffer addresses bus-segment voltage or power-state incompatibility; it does not replace address planning. Keep the correct pull-ups and segment topology for the particular system, and use the buffer where the master and sequencer cannot safely share a direct bus connection.
Choose how the system will shut down
A power sequencer needs a control event to perform a deliberate down-sequence. If the system only monitors the falling 12 V input as a supervisor fault, the LTC2937 can turn all EN outputs off together. That is a simultaneous fault response, not a timed sequence that turns rails off in a defined order.
| Control approach | What it provides | Shutdown behavior |
|---|---|---|
| EEPROM configuration alone | Autonomous operation using stored settings; no separate ON-pin or bus command is required for startup behavior. | Does not by itself initiate an orderly down-sequence when the 12 V input falls. |
| Supervisor-channel fault response | Uses a monitored voltage fault as the trigger. | Turns EN outputs off together; not a timed, ordered shutdown. |
| ON pin | Provides an explicit local control input for the sequencer. | Can initiate the configured down-sequence. |
| I²C/SMBus command | Lets a bus master command the sequencer. | Can initiate controlled shutdown when the system and bus master are available to issue the command. |
| LTC2955 driving ON | Provides defined voltage-level control of the LTC2937 ON pin and a manual pushbutton interface. | Supports deliberate on/off control; a 10 µF VPWR hold-up capacitor is shown to keep the sequencer powered while it completes shutdown. |
If the 12 V input is expected to collapse, a long retry interval can reduce the chance of an immediate restart while the input is still falling. The part 1 design example recommends a 13.1-second FAULT_RESPONSE retry delay for that specific situation; it is an example setting, not a universal value for every supply or recovery requirement.
Add the LTC2955 for defined on/off control
The LTC2955 can drive the LTC2937 ON pin from defined voltage levels and adds a manual pushbutton. In the described circuit, a 10 µF capacitor on VPWR provides hold-up so the sequencer remains powered while it carries out shutdown. This approach is useful when the system needs a deliberate user or logic-controlled off event rather than relying on a falling-input fault.
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Size and validate hold-up for the actual system’s load and shutdown timing; the cited 10 µF value is the circuit value shown in the design guide, not a guarantee for every implementation.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Link LTC2937 devices to sequence more than six rails
One LTC2937 handles six channels. To coordinate more supplies, connect sequencers as a group using the shared signals below, while keeping their I²C slave addresses distinct.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minute- SHARE_CLK: Connect across the LTC2937 devices and use one 3.3 kΩ pull-up to one VDD. Do not connect SHARE_CLK to unrelated points elsewhere in the system.
- SPCLK: Connect the devices’ SPCLK pins across the group as described in the design guide; do not route it to unrelated system points.
- FAULTB: Connect FAULTB across the group so fault signaling is shared between sequencers.
- ON: Tie the ON pins together when the devices need a consistent on/off state.
- I²C/SMBus: Assign a unique selected slave address to each device, even though sequencing signals are shared.
Shared sequencing signals coordinate devices; they do not increase the six channels available on an individual LTC2937. Plan how the rails are divided among devices and confirm the signal connections and address assignments before relying on the combined sequence.
Choose the implementation that matches the required behavior
- For a single six-rail group with autonomous startup: Configure and store the settings in EEPROM, then use LTpowerPlay to inspect the sequence and status during setup.
- For an orderly power-down: Add an explicit ON-pin control or have a bus master issue a command. Use the LTC2955 when a manual pushbutton and defined voltage-level control are needed.
- For a mixed-voltage or partially powered I²C system: Use a suitable bus buffer such as the LTC4313 between incompatible or independently powered segments.
- For more than six rails: Link multiple LTC2937 devices through SHARE_CLK, SPCLK, FAULTB, and, where consistent control is required, ON; give every device a unique I²C slave address.
- For a collapsing input supply: Do not mistake simultaneous fault-off for a controlled sequence. Provide a shutdown command path and ensure the sequencer has power for the required transition.
Timing values from the design guide
These values are context-specific reference points rather than universal settings. The source article’s 2 ms figure describes the approximate time for EEPROM settings to load into operating memory after VDD clears undervoltage lockout. Its stated fault-detection time is less than 35 µs for voltage excursions, ignoring short glitches. The 13.1-second FAULT_RESPONSE value is the example retry delay for a falling 12 V input, and 3.3 kΩ is the pull-up shown for SHARE_CLK in the minimalist and linked-device circuits. The controlled-shutdown circuit shows 10 µF on VPWR.
For configuration and debugging, LTpowerPlay is the software interface described for the LTC2937. The device and companion components are documented by Analog Devices’ LTC2937 product page, LTC4313 product page, and LTC2955 product page.
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