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User Manual
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V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Digital pulse width modulator
In bridge mode, the two halves of the switching cycle are identified as either the even half-cycle or the odd half-
cycle, as shown in the bottom part of
. This identification is used by the pulse generator to produce
pulses only on the correct half-cycle.
Register
rampX_half_mode
(X = 0, 1) is used to select between bridge and non-bridge topologies. This register
defines whether half-mode is enabled for the ramp. If the mode is enabled, the ramp count (ramp_max) equals
half of the switching period. Correspondingly, if half-mode is disabled, the ramp count equals the switching
period.
The switching period, T
switch
, is defined by the register
tswitchX
(X = 0, 1). It is automatically programmed by the
FW based on the PMBus command FREQUENCY_SWITCH, which sets the switching frequency in kHz. The
register
tswitchX
has LSB weight of 20 ns and range 0.0 to 10.22 µs. Therefore, there are some considerations
regarding FREQUENCY_SWITCH values:
•
Only values with corresponding T
switch
that are an exact multiple of 20 ns can be achieved.
•
If FREQUENCY_SWITCH is set to a value that cannot be achieved in
tswitchX
, the FW will choose the closest
achievable setting.
The closest achievable FREQUENCY_SWITCH to a target F
switch
can be found using Equation (7.1).
𝐹𝑅𝐸𝑄𝑈𝐸𝑁𝐶𝑌_𝑆𝑊𝐼𝑇𝐶𝐻 =
50𝑒6
𝑅𝑂𝑈𝑁𝐷(
50𝑒6
𝑡𝑎𝑟𝑔𝑒𝑡 𝐹𝑠𝑤𝑖𝑡𝑐ℎ
)
(7.1)
Note: 50e6 = 1/20e-9.
7.1.1
PWM ramp modulation schemes
The timing information provided by the ramp generator is a pair of timing markers called t1 and t2. These
timing markers are used by the pulse generator to define the rising and falling edges of the PWM pulses. The
timing markers are discussed further in the pulse generator
The XDPP1100 supports the following modulation schemes for placing t1 and t2:
•
Trailing edge (TE) modulation
•
Leading edge (LE) modulation
•
Dual edge (DE) modulation
These modulation schemes are shown in
. The first modulation waveform in
shows the TE
modulation case. The timing marker placement for TE modulation:
•
t1 is fixed at ramp count = 0
•
t2 is modulated based on the selected feedback control mode (
The example PWM pulse shown in
has a fixed LE and a modulated TE. The second modulation
scheme is LE modulation, shown in
. The timing marker placement for LE modulation is the
following:
•
t1 is modulated based on the selected feedback control mode (
•
t2 is fixed at ramp count = ramp_max
The example PWM pulse shown in
has a fixed TE and a modulated LE. The last modulation scheme
. In this modulation, the timing markers t1 and t2 are both modulated
based on the selected feedback control mode (
). The example PWM pulse shown in
modulated LE and TE.