ISL6263 데이터 시트보기 (PDF) - Renesas Electronics
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ISL6263 Datasheet PDF : 19 Pages
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ISL6263
current. This information is used exclusively to achieve the
IMVP-6+ load line as well as the overcurrent protection. It is
important to note that this current measurement should not be
confused with the synthetic current ripple information created
within the R3 modulator.
When using inductor DCR current sensing, an NTC element is
used to compensate the positive temperature coefficient of the
copper winding thus maintaining the load-line accuracy.
Processor Socket Kelvin Voltage Sensing
The remote voltage sense input pins VSEN and RTN of the
ISL6263 are to be terminated at the die of the GPU through
connections that mate at the processor socket. (The signal
names are Vcc_sense and Vss_sense respectively.) Kelvin
sensing allows the voltage regulator to tightly control the
processor voltage at the die, compensating for various
resistive voltage drops in the power delivery path.
Since the voltage feedback is sensed at the processor die,
removing the GPU will open the voltage feedback path of the
regulator, causing the output voltage to rise towards VIN. The
ISL6263 will shut down when the voltage between the VO and
VSS pins exceeds the severe overvoltage protection threshold
VOVPS of 1.55V. To prevent this issue from occurring, it is
recommended to install resistors Ropn1 and Ropn2 as shown
in Figure 5. These resistors provide voltage feedback from the
regulator local output in the absence of the GPU. These
resistors should be in the range of 20 to 100
VDIFF
VDD
OCP
10µA
OCSET
DROOP
VSUM
DFB
DROOP
VO
VSEN
RTN
ROCSET
PHASE
RS
CFILTER1
RFILTER1
RFILTER2
CFILTER2
CFILTER3
LOUT
DCR
COUT
ESR
VCC_SNS
VSS_SNS
To
Processor
Socket
Kelvin
Connections
FIGURE 5. SIMPLIFIED VOLTAGE DROOP CIRCUIT WITH GPU SOCKET KELVIN SENSING AND INDUCTOR DCR CURRENT SENSING
High Efficiency Diode Emulation Mode
The ISL6263 operates in continuous-conduction-mode (CCM)
during heavy load for minimum conduction loss by forcing the
low-side MOSFET to operate as a synchronous rectifier.
Depending upon the VID and FDE pin states, an improvement
in light-load efficiency can be achieved by operating in
discontinuous-conduction-mode (DCM) where the low-side
MOSFET is operated in diode-emulation-mode (DEM), forcing
the low-side MOSFET to block negative inductor current flow.
Positive-going inductor current flows from either the source of
the high-side MOSFET, or the drain of the low-side MOSFET.
Negative-going inductor current flows into the source of the
high-side MOSFET, or the drain of the low-side MOSFET.
When the low-side MOSFET conducts positive inductor
current, the phase voltage will be negative with respect to the
FN9213 Rev 2.00
June 10, 2010
VSS pin. Conversely, when the low-side MOSFET conducts
negative inductor current, the phase voltage will be positive
with respect to the VSS pin. Negative inductor current occurs
in CCM when the output load current is less than ½ the
inductor ripple current. Sinking negative inductor through the
low-side MOSFET lowers efficiency through unnecessary
conduction losses. Upon entering DEM the PWM switching
frequency is automatically shifted downward by an increase of
the window voltage VW of 33%. The PWM switching frequency
will continue to decrease as the load continues to decrease.
The reduction of PWM frequency further improves efficiency by
reducing switching losses. The converter will automatically
enter DEM after eight consecutive PWM pulses where the
PHASE pin has detected positive voltage shortly after the
LGATE pin has gone high. The converter will return to CCM on
the following cycle after the PHASE pin detects negative
Page 11 of 19
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