NQB-420DWA-AN Datasheet, PDF (23/36 Pages) CUI INC – FULLY REGULATED ADVANCED BUS CONVERTERS

CUI Inc │ SERIES: NQB-D │ DESCRIPTION: FULLY REGULATED ADVANCED BUS CONVERTERS
date 02/20/2013 │ page 23 of 36
Over Current Protection (OCP)
The product includes current limiting circuitry for
protection at continuous overload. The default setting for
the product is hic-up mode if the maximum output current
is exceeded and the output voltage is below 0.3×V_out, set
in command IOUT_OC_LV_FAULT_LIMIT (0x48). Above
the trip voltage value in command 0x48 the product will
continue operate while maintaining the output current at
the value set by IOUT_OC_FAULT_LIMIT (0x46). The load
distribution should be designed for the maximum output
short circuit current specified.
Droop Load Share variants (DLS) will enter hic-up mode,
with a trip voltage, 0.04×V_out, set in command IOUT_
OC_LV_FAULT_LIMIT (0x48). Above the trip voltage in
command (0x48) the product will continue operate while
maintaining the output current at the value set by IOUT_
OC_FAULT_LIMIT (0x46).
The over current protection of the product can be
reconfigured using the PMBus interface.
Input Over/Under voltage protection
The input of the product can be protected from high input
voltage and low input voltage. The over/under-voltage
fault level and fault response can be configured via the
PMBus interface.
Pre-bias Start-up Capability
The product has a Pre-bias start up functionality and will
not sink current during start up if a Pre-bias source is
present at the output terminals. If the Pre-bias voltage
is lower than the target value set in VOUT_COMMAND
(0x21), the product will ramp up to the target value. If
the Pre-bias voltage is higher than the target value set in
VOUT_COMMAND (0x21), the product will ramp down to
the target value and in this case sink current for a limited
of time set in the command TOFF_MAX_WARN_LIMIT
(0x66).
Switching frequency adjust using PMBus
The switching frequency is set to 140 kHz as default but
this can be reconfigured via the PMBus interface. The
product is optimized at this frequency but can run at
lower and higher frequency, (125-150 kHz). The electrical
performance can be affected if the switching frequency is
changed.
MFR_MULTI_PIN_CONFIG
The MFR_MULTI_PIN_CONFIG (0xF9) command enables
or disables different functions inside the product. This
command can be configured according to the table for
different functions.
Bit 7:6
00 = Stand alone
01 = Slave (N/A)
10 = DLS
11 = Master (N/A)
111111000000
000000000000
Bit 5
Power Good High Z 0 0 0 0 1 1 0 0 0 0 1 1
when active
Bit 4
Tracking enable
000000000000
(N/A)
Bit 3
External reference 0 0 0 0 0 0 0 0 0 0 0 0
(N/A)
Bit 2
Power Good
001111001111
Enable
Bit 1
Reserved
111111000000
Bit 0
Secondary Remote
Control Pull
010101010101
up/down resistor
enable 1)
1) When not used
with PMBus, the
CTRL input can be
internally pulled up
or down depending
on if it is active high
or low. When active
low it will be pulled
up and vice versa
Power Good
The product provides Power Good (PG) flag in the Status
Word register that indicates the output voltage is within a
specified tolerance of its target level and no fault condition
exists. If specified in section Connections, the product
also provides a PG signal output. The Power Good signal
is by default configured as active low, Push-pull and can
be re-configured via the PMBus interface. The Power Good
output can be configured as Push-pull or “High Z when
active” to permit AND’ing of parallel devices. It is not
recommended to use Push-pull when paralleling PG-pins,
see MFR_MULTI_PIN_CONFIG.
Synchronization, Tracking and External reference
This product does not support synchronization, tracking or
external reference.
The MFR_MULTI_PIN_CONFIG can be reconfigured using
the PMBus interface. Default configuration is set to Power
Good Push-Pull (0x04) for stand alone variants and DLS
Power Good Push-Pull (0x86) for Droop Load Share
variants.
User customized settings
This product has two data storage set: Default data (CUI
factory) and User data. The User data set’s priority is
higher than the Default data. The User data area is empty
while shipped to customer. After boot-up, if the controller
found no data stored in User data area, it will load Default
data instead.
Customer can change the RAM data and store the changes
into flash memory by PMBUS Store_User_All, next power
cycle will load the User data into RAM for execute.
Store_Default_All is write protected to ensure the factory
settings is always available for recovery.
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