NX2124/2124A
PIN DESCRIPTIONS
PIN #
1
PIN SYMBOL
BST
PIN DESCRIPTION
This pin supplies voltage to the high side driver. A high frequency
ceramic capacitor of 0.1 to 1 uF must be connected from this pin to SW pin.
High side MOSFET gate driver.
Ground pin.
Low side MOSFET gate driver. For the high current application, a 4.7nF capaci-
tor is recommended to be placed on low side MOSFET's gate to ground. This is
to prevent undesired Cdv/dt induced low side MOSFET's turn on to happen,
which is caused by fast voltage change on the drain of low side MOSFET in
synchronous buck converter and lower the system efficiency.
Voltage supply for the internal circuit as well as the low side MOSFET gate
driver. A 1uF high frequency ceramic capacitor must be connected from this pin
to GND pin.
This pin is the error amplifier inverting input. This pin is also connected to the
output UVLO comparator. When this pin falls below 0.56V, both HDRV and
LDRV outputs are in hiccup.
This pin is the output of the error amplifier and together with FB pin is used to
compensate the voltage control feedback loop. This pin is also used as a shut
down pin. When this pin is pulled below 0.3V, both drivers are turned off and
internal soft start is reset.
This pin is connected to the source of the high side MOSFET and provides
return path for the high side driver. Also SW senses the low side MOSFETS
current, when the pin voltage is lower than 360mV for NX2124, 540mV for NX2124A,
hiccup will be triggered.
2
3
4
HDRV
GND
LDRV
5
Vcc
6
FB
7
COMP
8
SW
Rev.1.8
02/28/08
4
MICROSEMI [ MICROSEMI CORPORATION ]
