Linear Technology LTC2977 Demo Board: Octal Power Supply Manager [Requires DC1613] DC2028A DC2028A Data Sheet
Product codes
DC2028A
LTC2977
17
2977fa
operaTion
EEPROM
The LTC2977 contains internal EEPROM (nonvolatile
The LTC2977 contains internal EEPROM (nonvolatile
memory) to store configuration settings and fault log
information. EEPROM endurance, retention, and mass
write operation time are specified over the operating junc-
tion temperature range. See Electrical Characteristics and
Absolute Maximum Ratings sections.
Nondestructive operation above T
Nondestructive operation above T
J
= 105°C is possible
although the Electrical Characteristics are not guaranteed
and the EEPROM will be degraded.
Operating the EEPROM above 105°C may result in a
Operating the EEPROM above 105°C may result in a
degradation of retention characteristics. The fault logging
function, which is useful in debugging system problems
that may occur at high temperatures, only writes to fault
log EEPROM locations. If occasional writes to these
registers occur above 105°C, a slight degradation in the
data retention characteristics of the fault log may occur.
It is recommended that the EEPROM not be written using
It is recommended that the EEPROM not be written using
STORE_USER_ALL or bulk programming when T
J
> 85°C.
The degradation in EEPROM retention for temperatures
>105°C can be approximated by calculating the dimen-
sionless acceleration factor using the following equation.
AF = e
Ea
k
•
1
T
USE
+
273
−
1
T
STRESS
+
273
Where:
AF = acceleration factor
Ea = activation energy = 1.4 eV
k = 8.625×10
AF = acceleration factor
Ea = activation energy = 1.4 eV
k = 8.625×10
−5
eV/°K
T
USE
= 105°C specified junction temperature
T
STRESS
= actual junction temperature °C
Example: Calculate the effect on retention when operating
at a junction temperature of 125°C for 10 hours.
T
T
STRESS
= 125°C
T
USE
= 105°C
AF = 8.65
Equivalent operating time at 105°C = 86.5 hours.
So the overall retention of the EEPROM was degraded by
So the overall retention of the EEPROM was degraded by
86.5 hours as a result of operation at a junction tempera-
ture of 125°C for 10 hours. Note that the effect of this
overstress is negligible when compared to the overall
EEPROM retention rating of 175,200 hours at a maximum
junction temperature of 105°C.
RESET
Holding the WDI/RESETB pin low for more than t
Holding the WDI/RESETB pin low for more than t
RESETB
will cause the LTC2977 to enter the power-on reset state.
While in the power-on reset state, the device will not
communicate on the I
2
C bus. Following the subsequent
rising-edge of the WDI/RESETB pin, the LTC2977 will
execute its power-on sequence per the user configuration
stored in EEPROM. Connect WDI/RESETB to VDD33 with
a 10k resistor. WDI/RESETB includes an internal 256µs
deglitch filter so additional filter capacitance on this pin
is not recommended.
WRITE-PROTECT PIN
The WP pin allows the user to write-protect the LTC2977’s
The WP pin allows the user to write-protect the LTC2977’s
configuration registers. The WP pin is active high, and
when asserted it provides Level 2 protection: all writes
are disabled except to the WRITE_PROTECT, PAGE,
MFR_EE_UNLOCK, STORE_USER_ALL, OPERATION,
MFR_PAGE_FF_MASK and CLEAR_FAULTS commands.
The most restrictive setting between the WP pin and
WRITE_PROTECT command will override. For example
if WP = 1 and WRITE_PROTECT = 0x80, then the
WRITE_PROTECT command overrides, since it is the
most restrictive.
OTHER OPERATIONS
Clock Sharing
Multiple LTC PMBus devices can synchronize their clocks
Multiple LTC PMBus devices can synchronize their clocks
in an application by connecting together the open-drain