Shutdown Mode: When the UVLO
pin is < 1.25V, the LM5171-Q1 is in the shutdown mode
with all gate drivers in the low state, and all internal logic reset. When UVLO <
1.25V, the device draws < 10μA through each of the HV1, HV2 and VCC pins.
Initialization Mode: When the
UVLO pin is > 1.5V but < 2.5V, and DT/SD > 0.5V, the LM5171-Q1 establishes proper internal logic states, and the LDODRV is turned on
to control the external MOSFET to produce the VCC, and LM5171-Q1 prepares for circuit operation. Once VCC voltage is >8.5V, VDD and
VREF are also established at approximately 5.0V and 3.5V, respectively.
Standby Mode: When the UVLO pin
is > 2.5V, and VCC > 8.5V, VDD> 4.5V, and DT/SD > 0.5V, the LM5171-Q1 is ready to operate. The oscillator is activated
and the SYNCO is firing phase-shifted clock signals, but the four gate drive outputs
remain off until the EN1 or EN2 initiate the power delivery mode.
Power Delivery Mode: When the
UVLO pin > 2.5V, VCC > 8.5V, VDD > 4.5V, DT/SD > 0.5V, EN1 or EN2 > 2V,
DIR1 and/or DIR2 is valid (> 2V or < 1V), the SS capacitor is released. Once the
SS voltage rises above 1V, the LM5171-Q1 gate drivers start
to switch and start the power delivery.
Latch-ed Shutdown mode serves as
an emergency shutdown function, and it is achieved by pulling DT/SD pin below 1V for at
least 2.5μs by an external circuit during operation. In latched shutdown mode, all gate
drivers remain in the low state, and both SS/DEM1 and SS/DEM2 pins are held low. The
latch can be reset by pulling the UVLO to below 1.25V for at least 10μs.