LTC3882_15 Datasheet, PDF (29/104 Pages) Linear Technology – Dual Output PolyPhase Step-Down DC/DC Voltage Mode Controller with Digital Power System Management

LTC3882
OPERATION
Factory Default Operation
The LTC3882 ships from the factory with a default con-
figuration stored in its non-volatile memory, unless custom
programming has been requested. These command values
are loaded into volatile RAM when the chip is initialized.
Prior to receiving any PMBus commands, a stock LTC3882
will operate in the factory default mode. If a STORE_USER_
ALL command is executed, the contents of the non-volatile
memory are replaced with active command values from
internal RAM, and that will permanently overwrite the factory
defaults. Table 5 summarizes the default factory operation
settings of the LTC3882 if all resistor configuration pins are
left open. These defaults allow parameters listed in bold
text in the table to be overridden with configuration resistor
programming. Warning limits are given in Table 5 because
exceeding them will cause the ALERT pin to be asserted even
if the PMBus interface is not being utilized.
Table 5. Factory Default Operation Summary
PARAMETER*
DEFAULT SETTING
PMBus Address
All writes enabled to Channel 0 at address 0x4F (no PEC).
Operation
OPERATION enabled with RUN pin control and soft-off.
Input Voltage OFF Threshold
6.0
Input Voltage UV Warning Limit
6.3
Input Voltage ON Threshold
6.5
Input Voltage OV Fault Limit
15.5
Input Voltage OV Fault Response
Latch off.
Soft-Start Time
8 (with no delay).
Maximum Start-Up Time (TMAX)
10
TMAX Fault Response
Retry every 350ms.
Output Voltage UV Fault/Warning Limits
0.900/0.925
Output Voltage UV Fault Response
Retry every 350ms.
Output Voltage
1.000
Active Voltage Positioning
Disabled.
Output Voltage OV Warning/Fault Limits
1.075/1.100
Output Voltage OV Fault Response
Retry every 350ms.
Shut Down
8ms soft-off.
Output Current Sense Element
0.63mΩ with 3930ppm/°C TC.
Output Current OC Warning/Fault Limits
20/29.75
Output Current OC Fault Response
Ignore
PWM Switching Mode
Continuous inductor current only.
PWM Control Protocol
Three-State PWM.
PWM Switching Frequency
500
Channel 0/1 Phase
0/180
Internal Overtemperature Warning/Fault Limits
130/160
Internal Overtemperature Responses
Warning: EEPROM disabled; Fault: PWM disabled.
External Undertemperature Fault Limit
–40
External Undertemperature Fault Response
Retry every 350ms.
External Overtemperature Warning/Fault Limits 85/100
External Overtemperature Fault Response
Retry every 350ms.
GPIO
Asserts low for the following faults: V_OUT UV or OV, V_IN OV, external or internal OT,
external UT, TON_MAX, or output short cycle.
ALERT Masking
ALERTs are masked for loss of PLL lock and external GPIO inputs.
*bold entries can be changed with external configuration resistors
UNITS
–
–
V
V
V
V
–
ms
ms
–
V
–
V
–
V
–
–
–
A
–
–
–
kHz
Degrees
°C
–
°C
–
°C
–
–
–
3882f
For more information www.linear.com/LTC3882
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