STBB1PUR Datasheet, PDF (10/21 Pages) STMicroelectronics – 1 A, high efficiency single inductor

Detailed description
STBB1XX
6.3
External synchronization
The STBB1 implements external synchronization pin. If and external clock signal is applied
to the MODE (SYN) pin with a frequency between 1.35 MHz and 2.0 MHz and with proper
low/high levels, the device automatically goes in PWM mode and the external clock is used
as switching oscillator.
6.4
Enable pin
The device operates when EN pin is set high. If EN pin is set low the device stops switching,
all the internal blocks are turned off. In this condition the current drawn from VIN/VINA is
below 1 µA in the whole temperature range. In addition the internal switches are in off state
so the load is electrically disconnected from the input, this avoids unwanted current leakage
from the input to the load.
6.5
6.5.1
6.5.2
6.5.3
Protection features
The STBB1 implements different types of protection features.
Soft-start and short-circuit
After the EN pin is pulled high, or after a suitable voltage is applied to VIN, VINA and EN the
device initiates the startup phase. The average current limit is set to 400 mA at the
beginning and is gradually increased while tracking the output voltage increase. As soon the
output voltage reaches 1.0 V the average current limit is set to its nominal value.
This method allows for a current limit proportional to the output voltage. If there is a short in
the V_OUT pin, the output current will not exceed 400 mA.
This process is not handled by a timer so the device is also able to start up even with large
capacitive loads.
Under-voltage lockout
The under voltage lockout function prevents improper operation of STBB1 when the input
voltage is not high enough. When the input voltage is below the VUVLO threshold the device
is in shutdown mode. The hysteresis of 100 mV prevents unstable operation when the input
voltage is close to the UVLO threshold.
Over-temperature protection
An internal temperature sensor continuously monitors the IC junction temperature. If the IC
temperature exceeds 140 °C typically the device stops operating. As soon as the
temperature falls below 120 °C typically normal operation is restored.
10/21
Doc ID 15474 Rev 5