8
dc2518af
DEMO MANUAL DC2518A
Overview
A simplified block diagram of the DC2518A is shown
in Figure 5. The LTC2975 measures input current with
a 10mΩ sense resistor. It also controls, monitors, and
supervises all four outputs.
Powering the Board
The DC2518A board is powered from a wall-powered 12V
supply. The supply must be capable of delivering > 1A. If
the four channels are loaded with the maximum allowable
current, the input current will be greater than 1A. The
LTC2975 device is powered either from the DC1613’s
3.3V power or jack power if V
IN
is applied.
DC2518A LEDs
There are three blue LEDs near the power jack. These
indicate that the DC jack has voltage and ±15V switching
regulator outputs are up and running. The LED labeled
VDD33 illuminates when the LTC2975 is powered from
either the USB controller or the external V
IN
power. Each
channel has its own green LED which indicates that the
channel is enabled. The red LEDs on ALERTB and FAULTB
indicate a warning or fault has occurred.
COMMON BOARD OPERATIONS
Reset the LTC2975
To reset the LTC2975 and reload the EEPROM contents into
operating memory (RAM), press the pushbutton switch
SW2 labeled RESET.
Preload the Outputs
Each of the outputs has preload resistors that provide
10mA of load. This ensures that the output voltage decays
to GND quickly when the channel is disabled. This is useful
when sequencing off then on quickly.
Controlling/Sequencing Channels
By default all four channels on the DC2518A board are
controlled by a single RUN switch.
The LTC2975 is pre-configured with different TON_DELAY
values for each channel. The TON_DELAY parameter is
applied to each of the channels relative to the CONTROL
pin or Group operation command to turn all channels “on”.
Figure 6 shows an oscilloscope screen capture of the four
output rails sequencing up.
The same applies to TOFF_DELAY values. When the Run
switch is set to the OFF position, all rails will power down
sequentially based on the TOFF_DELAY values.
PMBus
LDO
+12V
LDO
–12V
DC/DC
+48V
DC/DC
–48V
+3.3V
CH0
CH1
CH2
CH3
DC/DC
±15V
+V
IN
V
IN
dc2518a F05
V
PWR
CONTROL
I
IN_SNSM
V
IN_SNS
I
IN_SNSP
LTC2975
4-CH POWER
SYSTEM MANAGER
DC1613
USB DONGLE HEADER
RUN
SWITCH
INPUT
CURRENT SENSE
Figure 5. Simplified Block Diagram of the DC2518A
