LXDC2HN23A-324(2014) データシートの表示（PDF） - Murata Manufacturing
部品番号
コンポーネント説明
一致するリスト
LXDC2HN23A-324 Datasheet PDF : 31 Pages
| |||
LXDC2HN typeA series
Micro DC-DC converter
7. Detailed Description
PFM/PWM Mode
If the load current decreases, the converter will enter PFM mode automatically. In PFM mode, the device operates
in discontinuous current mode with a sporadic one switching pulse to keep high efficiency at light load.
The device uses constant on time control in PFM operation, which produces a low ripple voltage and accurate
output voltage compared with other PFM architectures. Because of the architecture, DC output voltage can be
kept within +/-2% range of the nominal voltage and the output ripple voltage in PFM mode can be reduced by just
increasing output capacitor.
The transition between PFM and PWM is also seamless and smooth.
The transition current between PFM and PWM is depend on Vin, Vout and other factors, but the ballpark threshold
is about 100-200mA
PFM mode at light load
PWM mode at heavy load
Nominal output voltage
UVLO (Under Voltage Lock Out)
The input voltage (Vin) must reach or exceed the UVLO voltage (1.4Vtyp) before the device begins the start up
sequence even when EN pin kept high. UVLO function keeps away of an unstable operation at low Vin range
Soft Start
The device has an internal soft-start function that limits the inrush current during start-up. The soft-start system
progressively increases the switching on-time from a minimum pulse-width to that of normal operation. Because
of the function, the output voltage increases gradually from zero to nominal voltage at start-up event. The nominal
soft-start time is 0.9msec. If you prefer a faster soft-start time, please contact Murata representative.
Enable
The device starts operation when EN is set high and starts up with soft start. For proper operation, the EN pin
must be terminated to logic high and must not be left floating. If the pin is left open, the device may operate at light
load but will not work at heavy load.
Pulling the EN pin to logic low forces the device shutdown. The device does not have a discharge function when it
turns off. If you prefer a discharge function, please contact Murata representative.
100% Duty Cycle Operation
The device can operate 100% duty cycle mode, in which high-side switch is constantly turned ON, thereby
providing a low input-to-output voltage difference.
When Vin and Vout becomes close and the duty gets close to 100%, the switching pulse will skip the nominal
switching period and the output voltage ripple may be larger than other condition. It should be noted that this
condition does not mean a failure of the device.
Over Current Protection
When the output current reaches the OCP threshold, the device narrows the switching duty and decrease the
output voltage. If the OCP event is removed within the mask time (20usec typ), the output voltage recovers to the
nominal value automatically. If the OCP event continues over the mask time, the device will shutdown.
After it is shut down, it can be restarted by toggling the Vin or EN voltage.
9
Dec 2014
Share Link: 