NCP81252
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DETAILED DESCRIPTION
General
The NCP81252, a single−phase synchronous buck
regulator, integrates power MOSFETs to provide a
high−efficiency and compact−footprint power management
solution for new generation computing CPUs. The device is
able to deliver up to 14 A TDC output current on an
adjustable output with SVID interface. Operating in high
switching frequency up to 1.2 MHz allows employing small
size inductors and capacitors while maintaining high
efficiency due to integrated solution with high performance
power MOSFETs. Current−mode RPM control with
feedforward from both input power supply and output
voltage ensures stable operation over wide operation
condition.
Current−Mode RPM Operation
The NCP81252 operates with the current−mode
Ramp−Pulse−Modulation (RPM) scheme in PS0/1/2/3
operation modes. In forced CCM mode, the inductor current
is always continuous and the device operates in quasi−fixed
switching frequency, which has a typical value programmed
by users through a resistor at pin FREQ. In auto CCM/DCM
mode, the inductor current is continuous and the device
operates in quasi−fixed switching frequency in medium and
heavy load range, while the inductor current becomes
discontinuous and the device automatically operates in PFM
mode with an adaptive fixed on time and variable switching
frequency in light load range.
Serial VID interface (SVID)
The NCP81252 supports Intel serial VID interface. It
communicates with the microprocessor through three wires
(SCLK, SDIO, ALERT#). For NCP81252, VID code
change rate is controlled by the SVID interface with three
options. Information regarding SVID interface can be
obtained from Intel.
Boot Voltage and SVID Address
Table 5 shows two boot voltage options of 0.9 V and
1.35 V programmed by an external 1% resistor Rvboot from
Vboot pin to GND, which programs SVID address as well.
Both values are set on power up and cannot be changed after
the initial power up sequence is complete.
Table 5. BOOT VOLTAGE AND SVID ADDRESS CONFIGURATION
Rvboot
(W)
Vboot Pin Voltage (mV)
Address
Vboot
(V)
Min Typ Max
0 0 0 102 0x0 0.9
14.0k
102 140 180 0x1 0.9
22.1k
180 219 258 0x2 0.9
30.1k
258 301 344 0x3 0.9
39.2k
344 391 438 0x4 0.9
48.7k
438 484 531 0x5 0.9
57.6k
531 578 625 0x6 0.9
68.1k
625 676 727 0x7 0.9
78.7k
727 781 836 0x8 0.9
88.7k
836 894 953 0x0 1.35
100k
953 1007 1062 0x1 1.35
113k
1062 1125 1188 0x2 1.35
124k
1188 1250 1312 0x3 1.35
137k
1312 1378 1445 0x4 1.35
150k
1445 1511 1578 0x5 1.35
165k
1578 1648 1719 0x6 1.35
178k
1719 1789 1859 0x7 1.35
196k
1859 1950 − 0x8 1.35
