LTC3577-3 AND LTC3577-4
5
REG0
through
REG3
text box windows display the hexa-
decimal value that has been written to the corresponding
registers of the LTC3577-3/LTC3577-4.
STATUS REG
text box window displays the hexadecimal
value that has been last read from the LTC3577-
3/LTC3577-4 status register.
BUCK1
through
BUCK3 MODE
select buttons are used to
individually set each buck regulator into Pulse Skip Mode
or Burst Mode for light loads.
BUCK SW SLEW RATE
option buttons are used to
choose one of four slew rates for optimal EMI reduction
or efficiency.
PWR_ON HI/LOW
select button is used to set the
PWR_ON pin high or low to turn on or off LDO2, VOUT1,
and VOUT2.
EN3 HI/LOW
select button is used to set the EN3 pin high
or low to turn on or off VOUT3.
AUTO READ BACK ENABLED/DISABLED
select button is
used to automatically update the status register every
250ms when enabled. When disabled the read register
may be updated by selecting the “Read Back Status” but-
ton.
Read Back Status
button is used to update the status
register when selected.
AUTO UPDATE ENABLED/DISABLED
select button is
used to automatically update the LTC3577-3/LTC3577-4
I
2
C registers when any of the Buck or LED buttons or
sliders have been changed. When disabled the LTC3577-
3/LTC3577-4 I
2
C registers may be updated by selecting
the “Update All Registers” button.
Update All Registers
button is used to update all of the
LTC3577-3/LTC3577-4 I
2
C write registers when selected.
LED EN/DIS
select button is used to enable or disable the
LED boost controller.
BOOST SW SLEW RATE FAST/SLOW
button is used to
turn on and off the LED switch faster or slower for opti-
mal efficiency or EMI reduction.
LED MODE
option buttons are used to choose one of
three Boost controller modes. CC Boost mode is a con-
stant current mode that allows the LED current to be
controlled by the LED DAC REG vertical slider. HV Boost
mode regulates the ILED pin to 0.8V to operate the Boost
at a fixed voltage.
HV Boost mode should not be enabled
unless the demo circuit has been modified to support
this mode of operation.
PWM mode allows the LED in-
tensity to be controlled by pulse width modulating the
LEDs based on the LED DAC REG, PWM Numerator,
PWM Denominator, and PWM Clock Speed settings.
NOTE:
When in CC Boost or HV Boost LED modes, the PWM controls
are disabled.
GRADATION TIME
option buttons set the desired time to
gradate up to or down from the selected LED intensity
whenever the LED controller is enabled or disabled.
LED DAC REG
vertical slider controls the LED current
from 20uA to 20mA in 64 logarithmic steps. The LED
intensity slider may be adjusted by clicking on the up or
down arrows to increment or decrement by one LSB or
by clicking and dragging the slide pointer. The hex code
and LED current is displayed in the two text boxes below
the slider.
PWM Clock Speed
option buttons are used to select the
PWM clock speed. The PWM clock speed is divided by
the PWM denominator to determine the PWM frequency.
PWM Numerator
vertical slider is used to select a PWM
numerator value. The PWM numerator is divided by the
PWM denominator to determine the PWM duty cycle.
PWM Denominator
vertical slider is used select a PWM
denominator value. The PWM denominator is used in
conjunction with the PWM numerator to determine the
PWM duty cycle and with the PWM clock speed to de-
termine the PWM frequency.
STATUS
indicators display the charge, NTC, and power
status determined by the LTC3577-3/LTC3577-4 status
register.
