TS3406_13 Datasheet, PDF (3/7 Pages) Taiwan Semiconductor Company, Ltd – 600mA / 1.5MHz Synchronous Buck Converter

Block Diagram
TS3406
600mA / 1.5MHz Synchronous Buck Converter
Function Description
Operation
TS3406 is a monolithic switching mode Step-Down DC-DC converter. It utilizes internal MOSFETs to achieve high
efficiency and can generate very low output voltage by using internal reference at 0.6V. It operates at a fixed
switching frequency, and uses the slope compensated current mode architecture. This Step-Down DC-DC
Converter supplies 600mA output current at VCC = 3V with input voltage range from 2.5V to 5.5V.
Current Mode PWM Control
Slope compensated current mode PWM control provides stable switching and cycle-by-cycle current limit for
excellent load and line responses and protection of the internal main switch (P-CH MOSFET) and synchronous
rectifier (N-CH MOSFET). During normal operation, the internal P-CH MOSFET is turned on for a certain time to
ramp the inductor current at each rising edge of the internal oscillator, and switched off when the peak inductor
current is above the error voltage. The current comparator, ICOMP, limits the peak inductor current. When the main
switch is off, the synchronous rectifier will be turned on immediately and stay on until either the inductor current
starts to reverse, as indicated by the current reversal comparator, IZERO, or the beginning of the next clock cycle.
The OVDET comparator controls output transient overshoots by turning the main switch off and keeping it off until
the fault is no longer present.
Idle Mode Operation
At very light loads, the TS3406 automatically enters Idle Mode. In the Idle Mode, the inductor current may reach
zero or reverse on each pulse. The PWM control loop will automatically skip pulses to maintain output regulation.
The bottom MOSFET is turned off by the current reversal comparator, IZERO and the switch voltage will ring. This
is discontinuous mode operation, and is normal behavior for the switching regulator. When the input voltage
decreases toward the value of the output voltage, the TS3406 allows the main switch to remain on for more than
one switching cycle and increases the duty cycle until it reaches 100%. The output voltage then is the input voltage
minus the voltage drop across the main switch and the inductor. At low input supply voltage, the RDS(ON) of the P-
CH MOSFET increases, and the efficiency of the converter decreases. Caution must be exercised to ensure the
heat dissipated not to exceed the maximum junction temperature of the IC.
3/7
Version: C12