ncp4200 ON Semiconductor, ncp4200 Datasheet - Page 15

• Manufacturer Part Number: ncp4200
• Description: Programmable Multi-phase Synchronous Buck Converter With Pmbus
• Manufacturer: ON Semiconductor

equation:
the serial interface. This is done using Bits <5:0> of the
VOUT_TRIM
Commands. The max offset that can be applied is
±193.75 mV (even if the sum of the offsets > 193.75 mV).
The LSB size is 6.25 mV. A positive offset is applied when
Bit 5 = 0. A negative offset is applied when Bit 5 = 1.
Dynamic VID
changing VID inputs while the controller is running. This
allows the output voltage to change while the supply is
running and supplying current to the load. This is commonly
referred to as Dynamic VID (DVID). A DVID can occur
under either light or heavy load conditions. The processor
signals the controller by changing the VID inputs (or by
programming a new VOUT_Command) in a single or
multiple steps from the start code to the finish code. This
change can be positive or negative.
change and ignores the DAC inputs for a minimum of 200
ns. This time prevents a false code due to logic skew while
the VID inputs are changing. Additionally, the first VID
change initiates the PWRGD and CROWBAR blanking
functions for a minimum of 100 ms to prevent a false
PWRGD or CROWBAR event. Each VID change resets the
internal timer.
5 msec to ensure that the code is correct before initiating a
shutdown of the controller.
code (0xD6) to limit the DVID slew rates. These can be
encountered when the system does a large single VID step
for power state changes, thus the DVID slew rate needs to
be limited to prevent large inrush currents.
of the Ton_Transition (0xD6) command code. Table 6
provides the soft−start values.
Table 5. Offset Codes
00 1000
10 0001
The value of R
An offset voltage can be added to the control voltage over
00 1111
The NCP4200 has the ability to respond to dynamically
When a VID bit changes state, the NCP4200 detects the
If a VID off code is detected the NCP4200 will wait for
The NCP4200 also uses the TON_Transition command
The transition slew rate is programmed using Bits <2:0>
VOUT_
CODE
TRIM
VOLTAGE
−6.25 mV
93.75 mV
OFFSET
50 mV
R
TRIM
B
(0xDB)
+
B
V
can be found using the following
VID
00 0010
10 0001
10 1110
VOUT_
CODE
* V
I
CAL
FB
and
ONL
VOUT_CAL
VOLTAGE
−87.5 mV
−6.25 mV
OFFSET
12.5 mV
CAL
−93.75 mV
VOLTAGE
OFFSET
62.5 mV
87.5 mV
TOTAL
(0xDC)
(eq. 9)
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15
Enhanced Transients Mode
for both load step up and load release. For load step up it
senses the output of the error amp to determine if a load step
up has occurred and then sequences on the appropriate
number of phases to ramp up the output current.
and uses the load release information to trigger the TRDET
pin, which is then used to adjust the error amp feedback for
optimal positioning. This is especially important during
high frequency load steps.
ensure proper sequencing and balancing of phases during
high frequency load steps as well as minimizing the stress on
components such as the input filter and MOSFETs.
Reference Current
This reference current sets I
programs the current based on the 1.8 V output.
Typically, R
Power Good Monitoring
via the CSREF pin. The PWRGD pin is an open−drain
output whose high level (when connected to a pullup
resistor) indicates that the output voltage is within the
nominal limits. The nominal limits specified in the
specifications above based on the VID voltage setting.
PWRGD goes low if the output voltage is outside of this
specified range, if the VID DAC inputs are in no CPU mode,
or whenever the EN pin is pulled low. PWRGD is blanked
during a DVID event for a period of 100 ms to prevent false
signals during the time the output is changing.
Table 6. Transition Rate Codes
The NCP4200 incorporates enhanced transient response
For load release, it also senses the output of the error amp
Additional information is used during load transients to
The I
The power good comparator monitors the output voltage
Code
REF
000
001
010
100
101
011
110
111
pin is used to set an internal current reference.
IREF
is set to 121 kW to program I
I
I
FB
REF
+ I
+
Transition Rate (V/msec)
REF
R
1.8 V
IREF
FB
+ 15 mA
. A resistor to ground
5 = default
13
15
11
1
3
7
9
REF
= 15 mA.
(eq. 10)
(eq. 11)