XRP7720 Datasheet, PDF (17/28 Pages) Exar Corporation – Quad Output Universal Customizable PMIC with PFM

XRP7720
Quad Output Universal Customizable PMIC with PFM
CLOCKS AND TIMING
PLL
System Clock
x4/x8
Reg
Frequency
Set Reg
DPWM
Base Frequency
2x
4x
Sequencer
Freg Mult Reg
SEL
CH1 Timing
To Channels 2®4
Figure 13 XRP7720 Timing Block Diagram
Figure 13 shows a simplified block diagram of
the XRP7720 timings. Again, please note that
the function blocks and signal names used are
chosen for ease of understanding and do not
necessarily reflect the actual design.
The system timings are generated by a
103MHz internal system clock (Sys_Clk). The
basic timing architecture is to divide the
Sys_Clk down to create a fundamental
switching frequency (Fsw_Fund) for all the
output channels that is settable from 105kHz
to 306kHz. The switching frequency for a
channel (Fsw_CHx) can then be selected as 1
times, 2 times or 4 times the fundamental
switching frequency.
To set the base frequency for the output
channels a “Fsw_Set” value representing the
base frequency shown in Table 1, is entered
into the switching frequency configuration
register. Note that the Fsw_Set value is
basically equal to the Sys_Clk divided by the
base frequency. The system timings are then
created by dividing down Sys_Clk to produce
a base frequency clock, 2X and 4X times the
base frequency clocks, and sequencing timing
to position the output channels relative to
each other. Each output channel then has its
own frequency multiplier register that is used
to select its final output switching frequency.
Table 1 shows the available channel switching
frequencies for the XRP7720 device. In
practice the PA 5.1 design tool handles all the
details and the user only has to enter the
fundamental switching frequency and the 1x,
2x, 4x frequency multiplier for each channel.
Base Frequency
kHz
105.5
107.3
109.1
111.0
112.9
115.0
117.0
119.2
121.5
123.8
126.2
128.8
131.4
134.1
137.0
139.9
143.1
146.3
149.7
153.3
157.0
160.9
165.1
169.4
174.0
178.8
183.9
189.3
195.1
201.2
207.7
214.6
222.0
229.9
238.4
247.6
257.5
268.2
279.9
292.6
306.5
Available 2x
Frequencies kHz
211.1
214.6
218.2
222.0
225.9
229.9
234.1
238.4
242.9
247.6
252.5
257.5
262.8
268.2
273.9
279.9
286.1
292.6
299.4
306.5
314.0
321.9
330.1
338.8
348.0
357.6
367.9
378.7
390.2
402.3
415.3
429.2
444.0
459.8
476.9
495.2
515.0
536.5
559.8
585.2
613.1
Table 1
Available 4x
Frequencies kHz
422.1
429.2
436.4
444.0
451.8
459.8
468.2
476.9
485.8
495.2
504.9
515.0
525.5
536.5
547.9
559.8
572.2
585.2
598.8
613.1
628.0
643.8
660.3
677.6
695.9
715.3
735.7
757.4
780.3
804.7
830.6
858.3
887.9
919.6
953.7
990.4
1030.0
1072.9
1119.6
1170.5
1226.2
© 2014 Exar Corporation
17/28
Rev. 1.0.0