With a general voltage regulator and a step-down DC/DC, the output voltage when IC is in standby status (when the operation is stopped) decreases to 0V.
With a step-up DC/DC converter, the output voltage when IC is in standby status (when the operation is stopped) varies depending on the IC. Step-up DC/DC converters, types, and functions can be roughly classified into four types.
1. Non-synchronous type
This is a general step-up DC/DC converter that uses diode.
As a diode is used, input side and output side cannot be disconnected in standby status and electrical connection is executed via diode.
A step-up DC/DC converter on which a driver is mounted operates in the same way as non-synchronous type step-up DC/DC converter when parasitic diode of a driver on High Side is not controlled.
2. Load disconnection function (product equipped with built-in Low Side/High Side driver FET)
The driver FET on High Side is controlled so that the output voltage becomes 0V in standby status.
(Driver FET: OFF, parasitic diode: anode Vout, cathode Lx)
The load disconnection function disconnects input side and output side in standby status.
With this function, the output voltage decreases to 0V to prevent malfunction of system and reduce the power consumption.
3. Bypass function (product equipped with built-in Low Side/High Side driver FET)
The driver FET on High Side is turned ON so that output side can be electrically connected with input in standby status.
With the bypass function, the input voltage can be passed through to the output side in standby status.
Utilizing this function can supply the battery voltage to the system side by setting it to standby status when MCU is in sleep status, for example. For RF that requires high supply voltage or at high-speed operation, voltage such as 3.3 V can be supplied to the system side by implementing the step-up operation.
The power consumption of whole system can be reduced by this voltage switching.
4. Vout "OR" type (product equipped with built-in Low Side/High Side driver FET)
This is Vout "OR" type enabling OR connection that applies external power supply to the output side.
With Vout "OR" type, input voltage and output voltage are monitored for both of step-up operation and standby status.
It determines which is higher, input voltage or output voltage, and controls the polarity of parasitic diode of High Side driver FET to prevent backward flow via parasitic diode.
