BD95242MUV Datasheet, PDF (8/21 Pages) Rohm – 2ch Switching Regurators for Desktop PC

Technical Note
●Pin Descriptions
・VIN
This is the main power supply pin. The input supply voltage range is 7V to 25V. The duty cycle of BD9524MUV is
determined by input voltage and control output voltage. Therefore, when VIN voltage fluctuated, the output voltage also
becomes unstable. Since VIN line is also the input voltage of switching regulator, stability depends on the impedance of
the voltage supply. It is recommended to establish bypass capacitor and CR filter suitable for the actual application.
・CTL
When CTL pin voltage is at least 2.3V the status of the linear regulator output becomes active (REG1=5V, REG2=3.3V).
Conversely, the status switches off when CTL pin voltage goes lower than 0.8V. The switching regulator doesn’t become
active when the status of CTL pin is low, if the status of EN pin is high.
・EN
When EN pin voltage is at least 2.3V, the status of the switching regulator becomes active. Conversely, the status switches
off when EN pin voltage goes lower than 0.8V.
・REG1
This is the output pin for 5V linear regulator and also active in power supply for driver and control circuit of the inside. The
standby function for REG1 is determined by CTL pin. The voltage is 5V, with 100mA current ability. It is recommended that
a 10uF capacitor (X5R or X7R) be established between REG1 and GND.
・REG2
This is the output pin for 3.3V linear regulator. The standby function for REG2 is determined by CTL. The voltage is 3.3V,
with 100mA current ability. It is recommended that a 10uF capacitor (X5R or X7R) be established between REG2 and
GND. It is available to set REF and SS by the resistance division value from REG2 in case REF are not set from an
external power supply.
・EXTVCC
This is the external input pin to REG1. When EXTVCC is beyond 4.4V, it supplies REG1 as EXTVCC is the power supply.
・REF
This is the setting pin for output voltage of switching regulator. It is so convenient to be synchronized to outside power
supply. This IC controls the voltage in the status of 2×REF≒FB.
・FB
This is the feedback pin from the output of switching regulator. This IC controls the voltage in the status of 2×REF≒FB.
・SS
This is the setting pin for soft start. The rising time is determined by the capacitor connected between SS and GND, and
the fixed current inside IC after it is the status of low in standby mode. It controls the output voltage till SS voltage catch up
the REF pin to become the double of the SS terminal voltage.
・FS
This is the input pin for setting the frequency. It is available to set it in frequency range is 200KHz to 500kHz.
・Is+
This is the sense pin for output current. In case it is connected to side of the coil resistance for sense current and the
voltage is set 65mV(typ) or more higher than FB pin voltage, the switching operation turns OFF.
・PGOOD
This is the open drain pin for deciding the output of switching regulator.
・MCTL
This is the switching shift pin for SLLM (Simple Light Load Mode). The efficiency in SLLM mode improves in setting MCTL
pin to 1.5V or more. In case MCTL terminal voltage range is from 1.5 to 3.0V, LG maximum OFF time is 40usec, from 4.5V
to REG1+0.3V, LG maximum OFF time is to infinity. It is in continuous mode that MCTL pin voltage is set 0.3V or less.
・AGND、DGND
This is the ground pin.
・BOOT
This is the power supply pin for high side FET driver. The maximum voltage range to GND pin is to 35V, to SW pin is to 7V.
In switching operations, the voltage swings from (VIN+REG1) to REG1 by BOOT pin operation.
・HG
This is the highside FET gate drive pin. It is operated in switching between BOOT to SW. In case the output MOS is 3ohm
/the status of Hi, 2ohm/the status of Low, it is operated hi-side FET gate in high speed.
・SW
This is the ground pin for high side FET drive. The maximum voltage range to GND pin is to 30V. Switching operation
swings from the status of BOOT to the status of GND.
・LG
This is the lowside FET gate drive pin. It is operated in switching between REG1 to PGND. In case the output MOS is
2ohm /the status of Hi, 0.5ohm/the status of Low, it is operated low-side FET gate in high speed.
・PGND
This is the ground pin for low side FET drive.
www.rohm.com
© 2009 ROHM Co., Ltd. All rights reserved.
8/20
2009.04 - Rev.B