COT Control, 3.0A Synchronous Step-Down DC/DC Converters
The XC9274 series is a group of synchronous-rectification type DC/DC converters with a built-in 51mΩ P-channel MOS driver transistor and 49mΩ N-channel MOS switching transistor, designed to allow the use of ceramic capacitors. The small on-resistances of these two internal driver transistors enable a high efficiency, stable power supply with an output current up to 3.0A. A 0.6V reference voltage source is incorporated, and the output voltage can be set freely by external resistors. Oscillation frequency is set to 1.2MHz or 3.0MHz can be selected for suiting to your particular application. The operation mode is HISAT-COT (*) control , allowing fast response, low ripple, and high efficiency over the full range of loads (from light loads to heavy loads).
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 0.25ms in typical for quick turn-on. Internal protection circuits include over current protection, short-circuit protection, and thermal shutdown circuits to enable safe use. Short-circuit protection is available only for B,C type. Hiccup mode is available only for D,E type. Soft-off function is available only for B, D type. The package is the SOP-8FD.
(*) HiSAT-COT is an original Torex term for High Speed Transient Response.
Typical Application Circuit
|Input Voltage Range||2.7V ～ 5.5V|
|Output Voltage Range||0.8V ～ 3.6V|
|FB Voltage||0.6V (±1.0%)|
|Efficiency||95%(VIN=5.0V, VOUT=3.3V, IOUT=1.0A)|
|Operating Ambient Temperature||- 40℃ ～ + 105℃|
|Environmentally Friendly||EU RoHS Compliant, Pb Free|
|Package||SOP-8FD||Number of Pins||8|
|Pcs/Reel||1,000||Package Size(mm)||6.0 x 4.9 x 1.55|
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.