SLVSGJ6 April 2022 TLVM13660
PRODUCTION DATA
VCC is the output of the internal LDO subregulator used to supply the control circuits of the TLVM13660. The nominal VCC voltage is 3.3 V. The VLDOIN pin is the input to the internal LDO. Connect this input to VOUT to provide the lowest possible input supply current. If the VLDOIN voltage is less than 3.1 V, VIN1 and VIN2 directly power the internal LDO.
To prevent unsafe operation, VCC has UVLO protection that prevents switching if the internal voltage is too low. See VCC_UVLO and VCC_UVLO_HYS in the Electrical Characteristics.
VCC must not be used to power external circuitry. Do not load VCC or short it to ground. VLDOIN is an optional input to the internal LDO. Connect an optional high quality 0.1-µF to 1-µF capacitor from VLDOIN to AGND for improved noise immunity.
The LDO provides the VCC voltage from one of two inputs: VIN or VLDOIN. When VLDOIN is tied to ground or below 3.1 V, the LDO derives power from VIN. The LDO input becomes VLDOIN when VLDOIN is tied to a voltage above 3.1 V. The VLDOIN voltage must not exceed both VIN and 12 V.
Equation 8 specifies the LDO power loss reduction as:
The VLDOIN input provides an option to supply the LDO with a lower voltage than VIN, thus minimizing the LDO input voltage relative to VCC and reducing power loss. For example, if the LDO current is 10 mA at 1 MHz with VIN = 24 V and VOUT = 5 V, the LDO power loss with VLDOIN tied to ground is 10 mA × (24 V – 3.3 V) = 207 mW, while the loss with VLDOIN tied to VOUT is equal to 10 mA × (5 V – 3.3 V) = 17 mW – a reduction of 190 mW.
Figure 8-4 and Figure 8-5 show typical efficiency plots with and without VLDOIN connected to VOUT.
VIN = 24 V | VOUT = 5 V | FSW = 1 MHz |
VIN = 36 V | VOUT = 5 V | FSW = 1 MHz |