1A COT Control, Synchronous Step-Down DC/DC Converters
The XC9258 series is a group of synchronous-rectification type DC/DC converters with a built-in P-channel MOS driver transistor and N-channel MOS switching transistor, designed to allow the use of ceramic capacitors.
Output voltage is internally set in a range from 0.8V to 3.6V (±2.0%) increments of 0.05V. The device provides a high efficiency, stable power supply with an output current of 600mA to be configured using only a coil and two capacitors connected externally. Oscillation frequency is set to 1.2MHz or 6MHz can be selected for suiting to your particular application.
During stand-by, all circuits are shutdown to reduce current consumption to as low as 1.0μA or less. As for the soft-start function as fast as 0.30ms in typical for quick turn-on. With the built-in UVLO (Under Voltage Lock Out) function, the internal P-channel MOS driver transistor is forced OFF when input voltage becomes 1.6V or lower. The B types integrate CL discharge function which enables the electric charge at the output capacitor CL to be discharged via the internal discharge.
Two types of package SOT-25, USP-6C are available.
(*) HiSAT-COT is an original Torex term for High Speed Transient Response.
|May 22, 2015||
|1.0A Step-down Synchronous DC/DC Converters with HiSAT-COT Fast Transient Response Control XC9257/XC9258 Series|
Typical Application Circuit
|Input Voltage Range||2.5V～5.5V|
|Output Voltage Range||0.8V～3.6V(±2.0%)|
|Protection Circuits||Thermal Shut Down
Short Circuit Protection(TypeB)
|Capacitor||Low ESR Ceramic|
|Environmentally Friendly||EU RoHS compliant, Pb free|
|Package||SOT-25||Number of Pins||5|
|Pcs/Reel||3,000||Package Size(mm)||2.8 x 2.9 x 1.3|
|Package||USP-6C||Number of Pins||6|
|Pcs/Reel||3,000||Package Size(mm)||1.8 x 2.0 x 0.6|
How does the GO function of DC/DC converters work? Does it work just like a regulator?
Torex regard the PWM/PFM automatic switch control function as Green Operation (GO) in the case of DC/DC. The GO function is defined as the switching operation between the PFM mode for a small output current and the PWM mode for a large output current. The PFM control method controls the output current by increasing and decreasing the fall time according to the output current while keeping a pulse width. The PWM control method controls the output current by adjusting the pulse width of the rise time, which keeps the rise/fall time interval constant and increases the efficiency at a heavy load. By switching between the PFM control for a small output current and the PWM control for a large output current, the quiescent current can be controlled for both of heavy and light loads.
How does the CL discharge function work?
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.
What does CL mean?
Load capacitor. Other companies often refer to it as COUT.
What does the FB product mean?
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
How does UVLO (under voltage lockout) work?
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.