11
dc2313af
DEMO MANUAL DC2313A
software controL with LtpowerpLay
Clicking the “Demoboard Defaults” menu item stores
default register settings in RAM, issues a CLEAR com-
mand, then executes a STORE command to store the RAM
contents into EEPROM. This places the LTC2937 back
into its default setting for the demo board. Note that this
procedure only works if the ASEL jumpers are configured
in their default settings:
ASEL1 = HI
ASEL2 = HI
ASEL3 = HI
ON/OFF CONTROl
The LTC2937 provides control over all of its functions
through the register interface. This includes ON/OFF con-
trol. The part can respond to the hardware ON/OFF pin, or
to a register ON/OFF bit, or to both. In this exercise, we
will sequence the system up and down using the I
2
C bus
command, ignoring the hardware ON/OFF pin. To program
the part to turn on and off through the I
2
C bus:
1) Start with the part sequenced-down (PB_EN LED is off,
LDOs are off).
2) Program register ON_OFF_CONTROL (0x02) by clicking
the checkboxes for each bit to sequence-up via the I
2
C
bus:
b[2] = 0 (ignore the ON input pin)
b[3] = 1 (honor the software ON/OFF bit)
b[4] = 1 (software ON/OFF state is ON)
4) The supplies sequence-up normally
The ENn LEDs will illuminate in sequence: 1-6.
The CHn LEDs will illuminate in sequence with the
ENn LEDs.
The RST LED will turn off after the last CHn LED
illuminates.
The LTC2937 Chip Dashboard in LTpowerPlay
tracks the internal register status in real time as it
sequences-up.
3) Send the register updates from LTpowerPlay to the
LTC2937 by pressing the Write All Button:
In the LTC2937 internal registers:
The ON_OFF_CONTROL[7] bit becomes set, indicat-
ing that the part is commanded to sequence-up.
The STATUS_INFORMATION[11:10] bits cycle
through the sequence-up states:
00b : sequence-down complete
01b : sequence-up in-progress
11b : sequence-up complete
The SEQ_POSITION_COUNT[9:0] bits count through
the sequence-up states (1 – 7).
The FAULT LED will remain off.
The ALERT LED will remain off.
The PB_EN and GLOBAL_ON LEDs will remain off.
The ON pin is low.
The default voltage (UV and OV) limits and timing
parameters should not detect faults.
