2A Synchronous Step-Down DC/DC Converters
The XC9243 series is a group of synchronous-rectification step-down DC/DC converters with a built-in 0.11Ω(TYP.) P-ch MOS driver transistor and 0.12Ω(TYP.) N-ch 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 2A. The XC9243 series has operating voltage range of 2.7V~6.0V and a 0.8V (±2.0%) reference voltage, and using externally connected resistors, the output voltage can be set freely from 0.9V.
With an internal switching frequency of 1.2MHz or 2.4MHz, small external components can be used.
The series have a high speed soft-start as fast as 1ms in typical for quick turn-on. It’s suitable for large-current application due to limit current is configured 4.0A in typical. During stand-by, all circuits are shutdown to reduce current consumption to as low as 1.0μA or less.
The integrated CL discharge function which enables the electric charge at the output capacitor CL to be discharged via the internal discharge switch located between the LX and VSS pins. Due to CL discharge function, malfunction on LX is prevented when Stand-by mode. With the built-in UVLO (Under Voltage Lock Out) function, the internal P-channel driver transistor is forced OFF when input voltage becomes 2.5V or lower. The series are available in USP-10B and SOP-8FD packages.
|Sep 5, 2012||
|New SOP-8FD Package Added, 2A Synchronous Step-Down DC/DC Converters, XC9242/XC9243 Series|
|Sep 9, 2011||
|【New Product Release】XC9242/XC9243 Series|
|Apr 26, 2011||
|2A Synchronous Step-Down DC/DC Converters XC9242/XC9243 Series|
Typical Application Circuit
|Driver Transistor||0.11Ω P-ch Driver Transistor
0.12Ω N-ch Switching Transistor
|Input Voltage Range||2.7V～6.0V|
|Output Voltage Range||0.9V～VIN|
|Maximum Duty Cycle||100%|
|Functions||Soft-Start,CL Discharge,Current Limit(Automatic return),Thermal Shut Down,UVLO|
|Capacitor||Low ESR Ceramic|
|Control Methods||PWM/PFM Auto|
|Operating Ambient Temperature||-40℃~+85℃|
|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 1.75|
|Package||USP-10B||Number of Pins||10|
|Pcs/Reel||3,000||Package Size(mm)||2.6 x 2.9 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.
What is the soft-start function?
The function to soften the rise to prevent the inrush current.
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 is the standby current?
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.
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.