User Manual
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V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Digital pulse width modulator
7.3.4
Forced duty cycle T1, T2
The XDPP1100 provides several methods through different registers for overriding the HW computed duty cycle
or PW. The registers used for overriding the duty cycle are:
•
pid_force_duty
and
pid_force_duty_en
•
rampX_force_duty
and
rampX_force_duty_en
•
rampX_force_t1
and
rampX_force_t1_en
•
rampX_force_t2
and
rampX_force_t2_en
The first method was already discussed in the compensator chapter, in
be forced at the PID output using the registers
pid_force_duty
and
pid_force_duty_en
. Regarding this
method, it should be emphasized that:
•
In a dual-phase system these registers can be used to apply the same duty cycle to both ramps
simultaneously.
•
These settings are applied before the current balance adjustment, and if current balance function is
required, this is the only method to override the duty cycle.
•
These PID override parameters are stored in the OTP so they can be used to configure the XDPP1100 to
apply permanent fixed duty cycle in an open-loop control mode without applying a FW patch.
The second method overrides the duty using registers
rampX_force_duty
and
rampX_force_duty_en
and it is
applied subsequent to the current balance adjustment, as was shown in
. The operation of this duty
override is the following:
•
rampX_force_duty
is applied at the beginning of the next ramp cycle (i.e., ramp = 0) after
rampX_force_duty_en
is set to 1.
•
Subsequent changes to
rampX_force_duty
are applied at the beginning of the next ramp cycle after the
change
It is possible to monitor when the new duty cycle force has been applied on the ramp. This can be done by
observing the register
rampX_dutyc_force_status
bit. This register bit is:
•
Cleared to 0, when either
rampX_force_duty
or
rampX_force_duty_en
change
•
Set to 1, when new duty-cycle force has been applied on the ramp at the start of the next ramp cycle
The ramp-based override parameters are preferred when each ramp requires a different duty cycle or when the
current balance adjustment must be temporarily or permanently overridden. The ramp override parameters
are not stored in the OTP, so therefore the FW-control is required to apply these parameters.
For the last two methods, registers
rampX_force_t1
and
rampX_force_t1_en
may be used to override the HW
computed t1_val, and registers
rampX_force_t2
and
rampX_force_t2_en
may be used to override the HW
computed t2_val. In both cases the parameters are not stored in the OTP so FW control is required to apply
these parameters.
Both parameters
rampX_force_t1
and
rampX_force_t2
have an LSB resolution of 5 ns. It is possible to provide
additional time resolution to both t1 and t2 via
rampX_force_duty[5:0]
according to Equations (7.8) and (7.9)
when t1 and t2 are forced.
𝑡1_𝑣𝑎𝑙 = {𝑟𝑎𝑚𝑝𝑋_𝑓𝑜𝑟𝑐𝑒_𝑡1[10: 0], 𝑟𝑎𝑚𝑝𝑋_𝑓𝑜𝑟𝑐𝑒_𝑑𝑢𝑡𝑦[5: 0]}
(7.8)
𝑡2_𝑣𝑎𝑙 = {𝑟𝑎𝑚𝑝𝑋_𝑓𝑜𝑟𝑐𝑒_𝑡2[10: 0], 𝑟𝑎𝑚𝑝𝑋_𝑓𝑜𝑟𝑐𝑒_𝑑𝑢𝑡𝑦[5: 0]}
(7.9)
This method is useful under TE or LE modulation when either t1 or t2 is set to a fixed value, because both t1 and
t2 use the same
rampX_force_duty
parameter for the LSBs.
