Rainbow Electronics MAX16064 - Manual (Page 22)

MAX16064
±0.3% Accurate, Quad, Power-Supply Controller with
Active-Voltage Output Control and PMBus Interface
22 ______________________________________________________________________________________
SMBALERT Output Operation
SMBALERT is an optional interrupt signal defined in
Appendix A of the SMBus specification. The MAX16064
provides an output SMBALERT as this interrupt signal.
SMBALERT is an active-low, open-drain output and it
asserts to signal the PMBus master if any of the voltage
or temperature fault has occurred. Typically,
SMBALERT is connected to all other SMBALERT open-
drain signals in the system, creating a wired-OR func-
tion with all SMBALERT outputs. When the master is
interrupted by its SMBALERT input, it stops or finishes
the current bus transfer and places an alert response
address (ARA) on the bus. The slave that pulled the
SMBALERT signal low acknowledges the ARA and
places its own address on the bus, identifying itself to
the master as the slave that caused the interrupt.
SMBALERT deasserts when the MAX16064 responds to
the ARA. SMBALERT deasserts when all the fault condi-
tions are removed. SMBALERT is also cleared by the
CLEAR_FAULTS command.
ENOUT_ Operation
When power is applied, all ENOUT_ are held low. Upon
receiving a command to turn on the power supply,
ENOUT_ goes high. The polarity can be changed by
the ENOUT_POL bit of the MFR_MODE_OUTPUT com-
mand. Setting the bit to a 1 makes the ENOUT_ active
low. If the bit in the external EEPROM is set to 1, upon
power-up, the ENOUT_ is held low until the bit is copied
from the EEPROM to the on-chip register at which time
the ENOUT_ goes high. Upon receiving a command to
turn on the power supply, ENOUT_ goes low. It takes
1.60ms (typ) to copy the configuration bits from the
EEPROM to the on-chip registers.
EN Operation
The MAX16064 includes an enable input (EN) that con-
trols all ENOUT_ signals in conjunction with the
MFR_MODE command. Unless MFR_MODE.IGNORE_EN
is set, a below-threshold level on EN prevents any
ENOUT_ from turning on. Additionally, if the voltage at
EN falls below the 1.2V (typ) threshold during
OPERATION ON, the MAX16064 follows the fault action
in MFR_FAULT_RESPONSE.EN. Figure 9 shows a typi-
cal sequencing with MFR_MODE.IGNORE_EN = 0.
RESET
INITIALIZE
INTERNAL
REGISTERS
SET PMBus
ADDRESS
ACCORDING TO
A3:A1
VALID
EEPROM?
RESTORE
CONFIGURATION
FROM EEPROM
INTERNAL
REFERENCE
STABLE?
ENABLE PMBus
COMMUNICATION
PMBus
COMMAND?
Y
N
Y
Y
N
N
EXECUTE PMBus
COMMAND
ASSERT
SMBALERT
Figure 8. MAX16064 Initialization
Table 2. ENOUT_ Active State
ENOUT_
DEFAULT
STARTUP
STATE
MFR_MODE_OUTPUT.
ENOUT_POL
ENOUT_ ACTIVE
STATE
Low 0 Active high
Low 1 Active low