LTC2978A View Datasheet(PDF) - Linear Technology

Part Name

Description

MFG CO.

LTC2978A

8-Channel PMBus Power System Manager Featuring Accurate Output Voltage Measurement

Linear Technology 

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PMBus Command Description

Temperature Related Commands

OT_FAULT_LIMIT, OT_WARN_LIMIT, UT_WARN_LIMIT and UT_FAULT_LIMIT

These commands provide supervising limits for temperature.

Data Contents

BIT(S) SYMBOL

b[15:0] Ot_fault_limit[15:0],

Ot_warn_limit[15:0],

Ut_warn_limit[15:0],

Ut_fault_limit[15:0]

OPERATION

The data uses the L11 format.

Units: °C.

LTC2978A

Timer Limits

TON_DELAY, TON_RISE, TON_MAX_FAULT_LIMIT and TOFF_DELAY

These commands share the same format and provide sequencing and timer fault and warning delays in ms.

TON_DELAY sets the amount of time in milliseconds that a channel waits following the start of an ON sequence before

its VOUT_EN pin enables a DC/DC converter. This delay is counted using SHARE_CLK only.

TON_RISE sets the amount of time in ms that elapses after the power supply has been enabled until the LTC2978A’s

DAC soft-connects and servos the output voltage to the desired level if Mfr_dac_mode = 00b. This delay is counted

using SHARE_CLK only.

TON_MAX_FAULT_LIMIT is the maximum amount of time that the power supply being controlled by the LTC2978A

can attempt to power up the output without reaching the VOUT_UV_FAULT_LIMIT. If the output reaches VOUT_UV_

FAULT_LIMIT prior to TON_MAX_FAULT_LIMIT, the LTC2978A unmasks the VOUT_UV_FAULT_LIMIT threshold. If

it does not, then a TON_MAX_FAULT is declared. (Note that a value of zero means there is no limit to how long the

power supply can attempt to bring up its output voltage.) This delay is counted using SHARE_CLK only.

TOFF_DELAY is the amount of time that elapses after the CONTROLn pin and/or OPERATION command is deasserted

until the channel is disabled (soft-off). This delay is counted using SHARE_CLK if available, otherwise the internal

oscillator is used.

Data Contents

BIT(S) SYMBOL

OPERATION

b[15:0] Ton_delay[15:0],

The data uses the L11 format.

Ton_rise[15:0],

Ton_max_fault_limit[15:0],

Toff_delay[15:0],

The internal timers operate on a 10µs internal clock. The SHARE_CLK pin may be used to synchronize the

10µs timer.

Delays are rounded to the nearest 10µs

Units: ms. Max value: 655ms

For more information www.linear.com/LTC2978A

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