isl6590dr Intersil Corporation, isl6590dr Datasheet - Page 8

• Manufacturer Part Number: isl6590dr
• Description: Digital Multi-phase Pwm Controller For Core-voltage Regulation
• Manufacturer: Intersil Corporation

6-bit Voltage ADC (ISL6580)
Each of the ISL6580s contain a 6-bit voltage ADC that can
be used to measure the difference between the core voltage
at the output and a reference voltage that is set by the VID
information. The VID is sent to the designated ISL6580 via
the backside serial bus from the ISL6590 prior to soft start.
The voltage difference measured is sent via the ERR signal
serially to the ISL6590. Even though each ISL6580 has the
voltage ADC, only one of them is required to use it. This
mode is called the Regulation Mode. The conversion is
initiated with the SOC (Start Of Conversion) signal from the
ISL6580 pulsing high for two SYSCLK cycles. After another
two SYSCLK cycles, the 6 bits of data are shifted out of the
ISL6580 on the ERR signal, one bit every two SYSCLK
cycles, starting with the MSB.
Because the ADC uses a successive approximation
architecture, every two SYSCLK cycles converts one bit, for
a total of 12 SYSCLK cycles to make the 6-bit conversion.
With a 133.3MHz SYSCLK, 66.6MHz is the sample rate per
bit of the ADC and is also the serial data rate of the ERR0
signal. However, since the SOC signal initiates the sampling
process, the effective overall sample rate of the voltage
measuring system is equal to the SOC rate.
Window Comparator (ISL6580)
Each ISL6580 contains a window comparator. At least two
ISL6580s must be configured to use it. One is configured
with comparator trip levels for Transient Voltage Mode (ATR
described below) and the other for Over/Under Voltage
Mode which responds via the fault registers and is described
in detail under Fault Processing.
Adaptive Voltage Positioning (AVP)
The Adaptive Voltage Positioning section of the ISL6590
takes the average current of all the active ISL6580 channels
and passes it through an AVP gain factor and a low pass
filter. The AVP gain factor sets the slope of the load line so
that the voltage at high current loading is intentionally less
than the voltage at small current loading. The output of the
low pass filter is subtracted from the ADC voltage error (ERR
signal) to adjust the operating voltage position. The AVP
value is modified in the digital compensation block with the
coefficients stored in the ISL6590 memory. The resulting
modified output is sent to the PWM generator to adjust the
target output voltage for all phases with a voltage offset from
the nominal VID so that current and voltage transients can
better be accommodated.
Active Transient Response (ATR)
Voltage Transient Mode must be performed by one
ISL6580 in the system (but not one already processing
another mode). It is done by using the ATR signals between
the ISL6580 and ISL6590. When a large change in current
occurs at the load, a large voltage transient also occurs. The
ATRH and ATRL levels are designed to trigger a temporary
mode in which the PWM generator aligns all phases or
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ISL6590
removes all phases in order to quickly raise or lower the
output voltage. The event is short-lived and the controller
quickly returns to normal operation, but the result is an
instantaneous boost or reduction in output voltage to keep
the transient event within the required regulation window. An
ATR window comparator located in the designated ISL6580
generates the ATRH or ATRL indicator signals when the
event occurs. The ATRH and ATRL trip levels are offsets
from the VID voltage and are set in ISL6590 register 0883h,
each with a 4-bit word. The ATRH, ATRL, and VID values
from the ISL6590 memory are sent to the designated
ISL6580’s registers via the BSB prior to soft start. In the
ISL6580, these are added or subtracted from the VID target
value with 7.5mV LSB resolution to set the trip levels.
Whereas AVP is performed with slight, tightly controlled
modifications to the PWM duty cycle in the ISL6590 using
sampled current data from each phase, ATR is performed
with preset values and trips a comparator in a single
ISL6580. The ISL6580 ATRH or ATRL signals immediately
tell the PWM generator in the ISL6590 to enter the ATR
mode. For this reason, the ATR mode is able to react much
quicker than the sample rate derived AVP.
NAVP
PAVP
ATRL
ATRH
PVID
FIGURE 3. ADAPTIVE VOLTAGE POSITIONING AND ACTIVE
MAX=VID
MIN
TRANSIENT RESPONSE TRIP LEVELS
I
LOAD
=MIN
I
LOAD
=MAX