XRP7659 Datasheet, PDF (6/10 Pages) Exar Corporation – 1.5A 18V1.4MHz Non Synchronous Step-Down Regulator

XRP7 65 9
1 .5 A 1 8 V 1 .4 MHz Non Sy n ch r on ou s St ep - Dow n Reg u lat or
Fig. 16 : Onset of Over - voltage Protection , I OUT=1.5A
Fig. 17 : Over - voltage Recovery , I OUT=1.5A
Fig. 18 : Gain and Phase Margin Plots of XRP7659EVB
~60kHz Crossover frequency; ~50° Phase Margin
APPLICATION INFORMAT ION
The XRP7659 is a non - synchronous current -
mode step - down DC - DC converter capable of
driving a 1.5A load. The integrated high - side
MOSFET has been optimized to provide high
efficiency within XRP7659 operating ratings.
The high switching frequency of 1.4MHz allows
the use of a small inductor and a
correspondingly small output capacitor
that
reduce the solution size and cost . The high
switching frequency also provides a very fast
transient response as shown in figure 11. The
built in loop compensation , bootstrap diode
and soft - start further reduce component cost.
A host of protection features including UVLO,
OCP, OTP, OVP and short - circuit help insure
safe operation under abnormal operating
conditions.
PROGRAMMING THE OUTPU T VOLTAGE
To program V _OUT use a resistor divider R1/R2
as shown in figure 1. R1 in conjuncti on with
the internal compensation comprise s the loop
compensation. Calculate R2 from:
R2
R1
V_{OUT 1}
0.81V
A resistor selection guide for common values
of V _OUT is shown in table 1 .
© 2012 Exar Corporation
6/ 10
Rev. 1. 2.0