isl6262a Intersil Corporation, isl6262a Datasheet - Page 16

• Manufacturer Part Number: isl6262a
• Description: Two-phase Core Controller Santa Rosa, Imvp-6+
• Manufacturer: Intersil Corporation

Theory of Operation
The ISL6262A is a two-phase regulator implementing Intel
IMVP-6+ protocol and includes embedded gate drivers for
reduced system cost and board area. The regulator provides
optimum steady-state and transient performance for
microprocessor core applications up to 50A. System
efficiency is enhanced by idling one phase at low-current
and implementing automatic DCM-mode operation.
The heart of the ISL6262A is R
Robust Ripple Regulator modulator. The R
combines the best features of fixed frequency PWM and
hysteretic PWM while eliminating many of their
shortcomings. The ISL6262A modulator internally
synthesizes an analog of the inductor ripple current and
uses hysteretic comparators on those signals to establish
PWM pulse widths. Operating on these large-amplitude,
noise-free synthesized signals allows the ISL6262A to
achieve lower output ripple and lower phase jitter than either
conventional hysteretic or fixed frequency PWM controllers.
Unlike conventional hysteretic converters, the ISL6262A has
an error amplifier that allows the controller to maintain a
0.5% voltage regulation accuracy throughout the VID range
from 0.75V to 1.5V.
The hysteresis window voltage is relative to the error
amplifier output such that load current transients results in
increased switching frequency, which gives the R
a faster response than conventional fixed frequency PWM
controllers. Transient load current is inherently shared
between active phases due to the use of a common
hysteretic window voltage. Individual average phase
voltages are monitored and controlled to equally share the
static current among the active phases.
Start-Up Timing
With the controller's +5V VDD voltage above the POR
threshold, the start-up sequence begins when VR_ON
exceeds the 3.3V logic HIGH threshold. Approximately
100µs later, SOFT and VOUT begin ramping to the boot
voltage of 1.2V. At start-up, the regulator always operates in
a 2-phase CCM mode, regardless of control signal assertion
levels. During this internal, the SOFT cap is charged by
41µA current source. If the SOFT capacitor is selected to be
20nF, the SOFT ramp will be at 2mV/µs for a soft-start time
of 600µs. Once VOUT is within 10% of the boot voltage for
13 PWM cycles (43µs for frequency = 300kHz), then
CLK_EN# is pulled LOW and the SOFT cap is
charged/discharged by approximately 200µA. Therefore,
VOUT slews at +10mV/µs to the voltage set by the VID pins.
Approximately 7ms later, PGOOD is asserted HIGH. Typical
start-up timing is shown in Figure 34.
16
3
Technology™, Intersil’s
3
modulator
3
regulator
ISL6262A
Static Operation
After the start sequence, the output voltage will be regulated
to the value set by the VID inputs shown in Table 1. The
entire VID table is presented in the IntelIMVP-6+
specification. The ISL6262A will control the no-load output
voltage to an accuracy of ±0.5% over the range of 0.75V to
1.5V.
A fully-differential amplifier implements core voltage sensing
for precise voltage control at the microprocessor die. The
inputs to the amplifier are the VSEN and RTN pins.
As the load current increases from zero, the output voltage
will droop from the VID table value by an amount
proportional to current to achieve the IMVP-6+ load line. The
ISL6262A provides for current to be measured using either
resistors in series with the channel inductors as shown in the
application circuit of Figure 33, or using the intrinsic series
resistance of the inductors as shown in the application circuit
of Figure 32. In both cases, signals representing the inductor
currents are summed at VSUM, which is the non-inverting
input to the DROOP amplifier shown in the “Functional Block
Diagram” on page 8 of Figure 1. The voltage at the DROOP
pin minus the output voltage, VO´, is a high-bandwidth
VID6
FIGURE 34. SOFT-START WAVEFORMS USING A 20nF SOFT
TABLE 1. TRUNCATED VID TABLE FOR INTEL® IMVP-6+
0
0
0
0
0
0
0
1
1
V
VR_ON
SOFT AND VO
CLK_EN#
DD
IMVP-6+ PGOOD
100µs
VID5
0
0
0
0
0
1
1
1
1
SPECIFICATION
CAPACITOR
VID4
0
0
0
1
1
1
1
0
1
2mV/µs
13 SWITCHING CYCLES
VID3
0
0
0
0
1
0
1
0
1
10mV/µs
VBOOT
VID2
90%
-7ms
0
0
1
0
1
1
0
0
1
VID1
0
0
0
0
0
0
1
0
1
VID COMMANDED
VOLTAGE
VID0 VOUT (V)
0
1
1
1
0
1
1
0
1
December 23, 2008
1.5000
1.4875
1.4375
1.2875
1.15
0.8375
0.7625
0.3000
0.0000
FN6343.1