XCL101 datasheet(9/19 Pages) TOREX

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XCL101

Series

VDD MAX

RFB2

RFB1

Error

Amp.

Load

Disconnection

Controller

CE and Bypass

Controller

Logic

PFM

Comparator

Synch

Buffer

Drive

VBAT

VOUT

Current

Sense

Logic

VREF

CFB

Inductor

VSS

PFM

Controller

Logic

VDD

■

OPERATION EXPLANATION

The XCL101 Series consists of a standard voltage source, a PFM comparator, a Nch driver Tr, a Pch synchronous rectifier switch Tr, a current

sense circuit, a PFM control circuit and a CE control circuit, etc. (refer to the block diagram below.)

Current limit PFM control is used for the control method to make it difficult for the output voltage ripple to increase even when the switching

current is superimposed, so the product can be used within a wide voltage and current range. Further, because PFM control is used, it has

excellent transient response to support low capacity ceramic capacitors to realize a compact, high-performance boost DC/DC converter.

The synchronous driver and rectifier switch Tr efficiently sends the coil energy to the capacitor connected to the VOUT pin to achieve highly

efficient operation from low to high loads.

The electrical characteristics actual output voltage VOUT(E) is the PFM comparator threshold voltage shown in the block diagram. Therefore, the

booster circuit output voltage average value, including the peripheral components, depends on the ripple voltage, so this must be carefully

evaluated before being used in the actual product.

< Reference Voltage Source (VREF)>

The reference voltage source (VREF voltage) provides the reference voltage to ensure stable output voltage of the DC/DC converter.

< PFM Control >

①

The voltage from the output voltage divided by the division resistors RFB1 and RFB2 in the IC is used as feedback voltage (FB voltage), and the

PFM comparator is compared with the FB voltage and VREF. If the FB voltage is lower than VREF, the signal is sent to the buffer driver via the PFM

control circuit and the Nch driver Tr is turned ON. If the FB voltage is higher than VREF, the PFM comparator sends a signal that does not turn ON

the Nch driver Tr.

②

The current sense circuit monitors the current flowing in the Nch driver Tr connected to the Lx pin when the Nch driver Tr is ON. When the

prescribed PFM switching current (IPFM) is reached, the signal is sent to the buffer driver via the PFM control circuit to turn OFF the Nch driver Tr

and turn ON the Pch synchronous rectifier switch Tr.

③

The Pch synchronous rectifier switch Tr ON time (off time) is dynamically optimized internally. After the off time has passed, when the PFM

comparator confirms the VOUT voltage has exceeded the set voltage, a signal that does not allow the Nch driver Tr to be turned on is sent from the

PFM comparator to the PFM control circuit, but if the VOUT voltage remains lower than the set voltage, then Nch driver Tr ON is started.

The intervals of the above

①②③ linked operations are continuously adjusted in response to the load current to ensure the output voltage is kept

stable from low to high loads and that it is done with good efficiency.

VLX

VOUT

ILX

VLX

VOUT

ILX

VOUT(E)

VOUT Voltage

Average

VOUT(E)

IPFM

VOUT:50mV/div

VLX:2V/div

ILX:200mA/div

VOUT Voltage

Average

VBAT=VCE=2.0V、VOUT=3.3V、IOUT=20mA、L=4.7μH、CL=10μF、Ta=25℃

2[μs/div]

VBAT=VCE=2.0V、VOUT=3.3V、IOUT=70mA、L=4.7μH、CL=10μF、Ta=25℃

XCL101 Datasheet(PDF) 9 Page - Torex Semiconductor

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