NX2124/2124A
nected to the GND plane with multiple vias. One is not back to the resistor divider should not go through high
enough. This is very important. The same applies to the frequency signals.
output capacitors and input capacitors.
6. Hdrv and Ldrv pins should be as close to
9. All GNDs need to go directly thru via to GND plane.
10. The feedback part of the system should be kept
MOSFET gate as possible. The gate traces should be away from the inductor and other noise sources, and be
wide and short. A place for gate drv resistors is needed placed close to the IC.
to fine tune noise if needed.
11. In multilayer PCB, separate power ground and
7. Vcc capacitor, BST capacitor or any other by- analog ground. These two grounds must be connected
passing capacitor needs to be placed first around the IC together on the PC board layout at a single point. The
and as close as possible. The capacitor on comp to goal is to localize the high current path to a separate loop
GND or comp back to FB needs to be place as close to that does not interfere with the more sensitive analog con-
the pin as well as resistor divider.
8. The output sense line which is sensing output
trol function.
TYPICAL APPLICATION
Vin
+12V
C3
33uF
L2 1uH
C5
1uF
Cin
2 x 16SP180M
D1 MBR0530T1
Vin
+5V
C6
1uF
7
5
1
Vcc
HI=SD
M3
BST
C4
0.1uF
2
M1 IRF3706
L1 1uH
C1
220pF
C2
15nF
R4
5k
6
NX2124
Comp
Hdrv
SW
Ldrv
8
M2
2 x IRF3706
Fb
Gnd
3
4
C7 4.7nF
Co
2 x (1500uF,13mohm)
Vout
+1.8V,20A
R2
800
R1 1k
Figure 9 - High output current application of 2124
Rev.1.8
02/28/08
14
MICROSEMI [ MICROSEMI CORPORATION ]
