TS19721A
Taiwan Semiconductor
Document Number: DS_P0000195 5 Version: A15
APPLICATION INFORMATION
Start-up Current
The typical start-up current is around 45μA. The very low start-up current allows the PWM controller to operate with
a high value start-up resistor and reduce overall power dissipation.
UVLO(Under Voltage Lockout)
A hysteretic UVLO comparator is implemented in TS19721A. The turn-on and turn-off thresholds level are fixed at
17.5V and 8V respectively. This hysteresis shown in Fig.1 ensures that the start-up capacitor will be adequate to
supply the chip during start-up. For quick start-up of the LED driver, the start-up resistor & capacitor needs to
optimize for application.
LEB(Leading-Edge Blanking)
Each time the power MOSFET is switched on, a turn-on spike will inevitably occur at the sense resistor. A 400ns
leading-edge blanking time is built in to avoid a false trigger.. Conventional RC filtering can therefore be omitted.
During this blanking period, the current-limit comparator is disabled and cannot switch off the gate driver.
OCP(Over Current Protection)
The TS19721A has built-in cycle-by-cycle over-current protection functions available at the CS pin. When the CS
pin voltage is larger than V
OCP
(1.4V), the gate output will be turned off immediately to avoid over temperature
damage.
OVP (Over Voltage Protection) on V
CC
To prevent the LED driver from being damaged, the TS19721A has an integrated OVP on V
CC
. When the V
CC
voltage is higher than the V
OVP
(31V), the output MOSFET will be shut down immediately. The OVP on the V
CC
pin
will automatically recover.. If the OVP triggers, the output PWM pulses will be stopped until the V
CC
pin voltage
returns to the UVLO off level when the TS19721A will automatically recover as shown in Fig. 2.
Fig. 1
Fig. 2
