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2021-08-25
XDPP1100 technical reference manual
Digital power controller
Digital pulse width modulator
The pulse width, t2
–
t1, for all modulation schemes is given in Equation (7.2):
𝑡
2
− 𝑡
1
= 𝐷 ∗ 𝑟𝑎𝑚𝑝_𝑚𝑎𝑥
(7.2)
D is the duty-cycle output of the compensation filter in the case of VMC. It should be noted that the pulse
generator is also capable of creating a pulse with LE at t2 and TE at t1. This pulse would have a pulse width
equal to (1
–
D) * ramp_max. The modulation scheme for both ramps is selected via register
rampX_m_flavor
(X = 0, 1) as shown in
Table 36
Modulation type settings
rampX_m_flavor
Modulation type
0
Dual edge (DE)
1
Leading edge (LE)
2, 3
Trailing edge (TE)
7.1.2
PWM ramp synchronization
Both ramp generators, ramp0 and ramp1, are capable of synchronizing to an external sync signal. In addition,
ramp1 synchronizes to ramp0 even without the presence of an external sync signal. The synchronization is
programmed through the register
rampX_sync_sel
(X = 0, 1).
For ramp0 programming, the register
ramp0_sync_sel
should always be set to 1. Thus, ramp0 synchronizes to
an external sync pulse if provided. Otherwise, its period is defined by register
tswitch0
(PAGE0.FREQUENCY_SWITCH). For ramp1 programming, the regiser
ramp1_sync_sel
should be programmed
as follows:
•
Set to 1, in order to synchronize to ramp0. If ramp0 is synchronized to an external sync pulse, ramp1 also
synchronizes to this pulse. This setting should be chosen for a dual-loop system with F
switch1
= F
switch0
or a
single-loop system with an interleaved phase.
•
Set to 0, to use the period defined by register
t
switch1
(PAGE1.FREQUENCY_SWITCH). This setting should be
chosen for a dual-loop system with F
switch1
≠ F
switch0
or a single-loop system using only Loop 1 (not typical).
The ramp phase in relation to the external sync pulse, (or ramp1 to ramp0 for internal sync) is defined by the
register
rampX_phase
(X = 0, 1). This is illustrated in
. The value for
rampX_phase
is automatically
computed by the FW from the PMBus command PAGEX.INTERLEAVE as given in Equation (7.3).
𝑟𝑎𝑚𝑝𝑋_𝑝ℎ𝑎𝑠𝑒 =
256∗𝑃𝐴𝐺𝐸𝑋.𝐼𝑁𝑇𝐸𝑅𝐿𝐸𝐴𝑉𝐸[3:0]
𝑃𝐴𝐺𝐸𝑋.𝐼𝑁𝑇𝐸𝑅𝐿𝐸𝐴𝑉𝐸[7:4]
(7.3)