Technical Terms

QuestionWhat is the synchronous rectification?
Answer

For the step down DC/DC, MOSFET is used as a low side switch, instead of the schottky diode. In the synchronous rectification, the controller IC turns on MOSFET at the right time. Because MOSFET has the smaller on-resistance than the schottky, it can realize higher efficiency than the diode under the condition of low voltage and large current. It can also reduce the mounting area than using an external schottky.

QuestionWhat are the load-transient response characteristics?
Answer

It indicates how much the output voltage varies and how long the fluctuation takes to converge when the output current changes steeply. The load-transient response characteristics are affected by the IC characteristics, output current conditions, and CL capacitor. The high speed regulator has a better load-transient response but a larger supply current. A large CL capacitor has a large charge capability. It can prevent the drop of the output voltage but takes long time to recover the set output voltage after an IC response. If a low speed regulator with bad load transient response is selected, the output voltage may fluctuate beyond the range of the LSI operating voltage, witch resulting in malfunction. Care should be taken for selecting a regulator IC and CL capacitor.

QuestionWhat is the line-transient response?
Answer

When the input voltage is changed steeply, the output voltage varies. This is the index to indicate. How the output voltage quickly recover.

QuestionHow does the CL discharge function work?
Answer

The function rapidly releases the charge remained in the CL capacitor to make the VOUT pin voltage zero. The VOUT pin voltage does not reach zero immediately after being turned off by the CE function due to the charge remained in the connected CL capacitor. While the charge in the CL capacitor is gradually reaching zero, the LSI continues operating and does not work with the CE pin signal, which may cause a malfunction. This is why the discharge is required when turning off the CE pin. A larger capacitance of the capacitor needs longer time to be discharged.

QuestionWhat is the impedance?
Answer

This is the ratio of voltage to current of the AC circuit and indicates the difficulty of the current flow. The unit is Ω. It extends the concept of the electric resistance in the Ohm's law for DC to AC.

QuestionWhat does the watchdog timer work?
Answer

This timer function is continuously monitoring to check whether the microcomputer is normally operating or not and give notice of any abnormal operation.

QuestionWhat is the error amplifier?
Answer

The circuit that is continuously comparing the output voltage with the reference voltage to amplify the difference to control the signal to the controller transistor.

QuestionWhat is the open drain?
Answer

The output type of the CMOS logic IC that has the open drain output, which means that the drain of the output transistor is directly introduced to a pin without any internal connection.

QuestionWhat is the open loop gain?
Answer

The gain of the circuit without feedback, represented by the ratio of output voltage to input voltage in dB.

QuestionWhat does Active High mean?
Answer

This means a function operating at HIGH. The opposite is Active Low, which means a function operating at LOW.

QuestionWhat is the meaning of the VDD?
Answer

The voltage applied to the power-supply pin of the IC to drive it.

QuestionWhat is the VIN?
Answer

The voltage that is input to the circuit.

QuestionWhat is the threshold?
Answer

The value that is specified for a specific function to operate. The function is turned on and off by inputting voltage which is higher and lower than this value respectively. For CMOS circuits, an input value near the threshold may cause a misjudgment between H and L. To avoid such a case, many circuits employ a certain range of threshold, and consider the value which is equal to the upper limit or more as H and the value which is equal to the lower limit or less as L.

QuestionWhat is the HIGH voltage?
Answer

A voltage that is higher than the threshold.

QuestionWhat is the LOW voltage?
Answer

A voltage that is lower than the threshold.

QuestionWhat does USP stand for?
Answer

Ultra Small Package. It is a Torex's special micro package without projecting pins.

QuestionWhat is the Ohm's law?
Answer

V=I*R

QuestionWhat does CL mean?
Answer

Load capacitor. Other companies often refer to it as COUT.

QuestionWhat is the quiescent current?
Answer

The current, required for the IC operation, that flows through the IC with no load. For a mobile phone, remote control, and other applications of which the waiting time is long, an IC with a small quiescent current should be used to reduce the draining of the battery. An IC with a high speed transient response tends to have a large quiescent current.

QuestionWhat is the standby current?
Answer

The current that flows through the IC in the standby mode. The standby mode means the state where the IC has been turned off by the CE function.

QuestionWhat is the EXT pin?
Answer

The pin to which the switching pulse is output in DC/DC. It is connected to the gate of the MOS. The on time of this pulse defines duty cycle.

QuestionWhat does the FB product mean?
Answer

An IC for which any output voltage can be set by the reference voltage of the FB pins and the external dividing resistor. The output voltage is determined by the RFB1 and RFB2 values, using the following formula: VOUT = Vref × (RFB1 + RFB2)/RFB2

QuestionWhat type of product does the VOUT product mean?
Answer

The VOUT product means the one whose output voltage is preset and fixed by internal diverting resistors.

QuestionWhat is the load regulation?
Answer

It indicates how much the output voltage or output current varies when the load changes. This index represents how much the output voltage drops as the output current is increased.

QuestionWhat is the pulse skip (blocking oscillation)?
Answer

A phenomenon of the switching pulse skipping with a small input-output voltage difference, or at a step down/heavy load or step up/light load. Skipping pulses helps to keep the output voltage constant. It may be solved by adjusting the L inductance or the CL capacitance.

QuestionWhat is the switching frequency?
Answer

The switching cycle of an IC. It depends on the parasitic capacitance or inductance of the board layout or peripheral parts. It synchronizes with the ripple voltage.

QuestionHow does UVLO (under voltage lockout) work?
Answer

This circuit forcibly turns off the driver transistor when VIN drops below the UVLO voltage. If the input voltage recovers to the value which is equal to the specified value or more, UVLO will be released to resume the switching operation. It is resumed by the soft-start function. The paused state by UVLO is not the shutdown. The pulse output is stopped, but the internal circuit is operating.

QuestionWhat is PFM control and PWM control?
Answer

PFM control is a method to control the output current by maintaining a constant pulse width, and increasing and decreasing the OFF time according to the output current. Since the PWM control adjusts the pulse width of the ON time to control the output current, the cycle of the ON and OFF time becomes constant, which increases the efficiency during a heavy load. The current consumption during a heavy loading and light load is controlled by switching to PWM control when the output current is high, and to PFM control when the output current is low.

QuestionWhat is current limit PFM?
Answer

The current limit PFM control is a control method to turn OFF the switching when the current flowing into the coil reaches a certain value. In the case of a duty fixed type PFM, when the input/output voltage difference is large, the coil current by the switching also becomes high, which tends to increase the ripple. However, in the current limit PFM, when the input/output voltage difference is large, the ON time becomes shorter and the coil current also becomes lower, which reduces the ripple.

QuestionWhat is AEC?
Answer

AEC is an acronym for Automotive Electronics Council, which is a standards organization for automotive electronic component reliability established by major auto manufacturers and U.S. electronic component manufacturers.

QuestionWhat is AEC-Q100?
Answer

AEC-Q100 is a standard of the AEC which prescribes a variety of reliability tests for integrated circuits (ICs).

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