User Manual
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V 1.0
2021-08-25
XDPP1100 technical reference manual
Digital power controller
Voltage control
A simplified block diagram of the ramp generator is shown in
, where the target output voltage
consists of the sum of the following registers:
•
vc_vramp_target
, which is the VSEN referenced target voltage computed by FW from PMBus commands
according to Equation (5.1).
•
vc_vcontrol_delta
, which is the VSEN referenced offset voltage computed by FW from PMBus commands
according to Equation (5.2).
𝑣𝑐_𝑣𝑟𝑎𝑚𝑝_𝑡𝑎𝑟𝑔𝑒𝑡 = 𝑉𝑂𝑈𝑇_𝐶𝑂𝑀𝑀𝐴𝑁𝐷 ∗ 𝑉𝑂𝑈𝑇_𝑆𝐶𝐴𝐿𝐸_𝐿𝑂𝑂𝑃 ∗
6400
2
(16−𝑉𝑂𝑈𝑇_𝑀𝑂𝐷𝐸[4:0])
(5.1)
𝑣𝑐_𝑣𝑐𝑜𝑛𝑡𝑟𝑜𝑙_𝑑𝑒𝑙𝑡𝑎 = (𝑉𝑂𝑈𝑇_𝑇𝑅𝐼𝑀 + 𝑉𝑂𝑈𝑇_𝐶𝐴𝐿_𝑂𝐹𝐹𝑆𝐸𝑇) ∗ 𝑉𝑂𝑈𝑇_𝑆𝐶𝐴𝐿𝐸_𝐿𝑂𝑂𝑃 ∗
6400
2
(16−𝑉𝑂𝑈𝑇_𝑀𝑂𝐷𝐸[4:0])
(5.2)
Figure 40
Ramp generator diagram
The slew rate on the ramp generator output, vcontrol_ramp, is programmed via register
vc_vramp_tstep
. It
defines the time between 1.25 mV steps (referenced to VSEN) and it can be computed based on the PMBus
commands according to the following equations:
•
During soft-start: Equation (5.3)
•
During shutdown: Equation (5.4)
•
During regulation: Equation (5.5)
𝑣𝑐_𝑣𝑟𝑎𝑚𝑝_𝑡𝑠𝑡𝑒𝑝 = [
62.5∗2
22
∗𝑇𝑂𝑁_𝑅𝐼𝑆𝐸
𝑉𝑂𝑈𝑇_𝐶𝑂𝑀𝑀𝐴𝑁𝐷∗𝑉𝑂𝑈𝑇_𝑆𝐶𝐴𝐿𝐸_𝐿𝑂𝑂𝑃
] − 1
(5.3)
𝑣𝑐_𝑣𝑟𝑎𝑚𝑝_𝑡𝑠𝑡𝑒𝑝 = [
62.5∗2
22
∗𝑇𝑂𝐹𝐹_𝐹𝐴𝐿𝐿
𝑉𝑂𝑈𝑇_𝐶𝑂𝑀𝑀𝐴𝑁𝐷∗𝑉𝑂𝑈𝑇_𝑆𝐶𝐴𝐿𝐸_𝐿𝑂𝑂𝑃
] − 1
(5.4)
𝑣𝑐_𝑣𝑟𝑎𝑚𝑝_𝑡𝑠𝑡𝑒𝑝 = [
62.5∗2
19
𝑉𝑂𝑈𝑇_𝑇𝑅𝐴𝑁𝑆𝐼𝑇𝐼𝑂𝑁_𝑅𝐴𝑇𝐸∗𝑉𝑂𝑈𝑇_𝑆𝐶𝐴𝐿𝐸_𝐿𝑂𝑂𝑃
] − 1
(5.5)
The programmable slew rate on the vcontrol_ramp is possible to bypass through register
vc_vramp_load_immediate
. Setting this value high immediately loads the
vc_vramp_target
into ramp
output, bypassing the next step computation function. Otherwise, with the
vc_vramp_load_immediate
value
low, the ramp output is slewed to
vc_vramp_target
at a rate determined by register
vc_vramp_tstep
. The
intended use for this feature is to allow the FW to start the soft-start ramp from the measured pre-bias voltage.
vcontrol_ramp[14:0]
U12.3
vc_vramp_load_immediate
vc_vramp_target[14:0]
vc_vramp_target_window[7:0]
vc_vramp_tstep[15:0]
U12.3
U8.0
vc_vcontrol_at_target_window
vc_vcontrol_ramp_busy
vc_vcontrol_ramp_fall
vc_vcontrol_ramp_rise
vc_vcontrol_at_target
vc_vcontrol_delta[12:0]
S10.3
vc_vramp_on
LSB= 20ns
+
+
0
1
A
B
C
A = B
A > B
C < A < D
Next Step
Computation
D
A < B
50MHz
50MHz
+
+ +
-
S
S
S
D
Q
Q
SET
CLR
