isl6307b Intersil Corporation, isl6307b Datasheet - Page 15

• Manufacturer Part Number: isl6307b
• Description: 6-phase Vr11 Pwm Controller With 8-bit Vid Code Capable Of Precision Rds On Or Dcr Differential Current Sensing For Applications In Which Supply Voltage Is Higher Than 5v
• Manufacturer: Intersil Corporation

the temperature effect on the sensed current signal, a
Positive Temperature Coefficient (PTC) resistor can be
selected for the sense resistor R
temperature compensation function of ISL6307B should be
utilized. The integrated temperature compensation function
is described in the Temperature Compensation section.
Channel-Current Balance
The sensed current I
together and divided by the number of active channels. The
resulting average current I
total load current. Channel current balance is achieved by
comparing the sampled current of each channel to the
average current to make an appropriate adjustment to the
PWM duty cycle of each channel. Intersil’s patented current-
balance method is illustrated in Figure 7. In the figure, the
average current combines with the channel 1 current I
create an error signal I
the pulse width commanded by V
unbalance and force I
error signal correction is applied to each active channel.
Channel current balance is essential in achieving the
thermal advantage of multiphase operation. With good
current balance, the power loss is equally dissipated over
multiple devices and a greater area.
Voltage Regulation
The integrating compensation network shown in Figure 8
assures that the steady-state error in the output voltage is
limited only to the error in the reference voltage (output of
the DAC) and offset errors in the OFS current source,
remote-sense and error amplifiers. Intersil specifies the
guaranteed tolerance of the ISL6307B to include the
combined tolerances of each of these elements.
The output of the error amplifier, V
sawtooth waveform to generate the PWM signals. The PWM
signals control the timing of the Intersil MOSFET drivers and
regulate the converter output to the specified reference
FIGURE 7. CHANNEL-1 PWM FUNCTION AND CURRENT-
V
COMP
FILTER
BALANCE ADJUSTMENT
+
I
ER
-
+
f(jω)
I
1
n
ER
from each active channel are summed
-
ER
I
AVG
toward zero. The same method for
. The filtered error signal modifies
SAWTOOTH SIGNAL
AVG
15
÷ N
provides a measure of the
ISEN
COMP
COMP
+
-
, or the integrated
to correct any
, is compared to the
Σ
I
PWM1
I
I
I
I
6
5
4
3
2
1
to
ISL6307B
voltage. The internal and external circuitry which control
voltage regulation is illustrated in Figure 8.
The ISL6307B incorporates an internal differential remote-
sense amplifier in the feedback path. The amplifier removes
the voltage error encountered when measuring the output
voltage relative to the local controller ground reference point
resulting in a more accurate means of sensing output
voltage. Connect the microprocessor sense pins to the non-
inverting input, VSEN, and inverting input, RGND, of the
remote-sense amplifier. The remote-sense output, V
connected to the inverting input of the error amplifier through
an external resistor.
A digital to analog converter (DAC) generates a reference
voltage based on the state of logic signals at pins VID7
through VID0. The DAC decodes the 8-bit logic signal (VID)
into one of the discrete voltages shown in Table 1. Each VID
input offers a 45µA pull-up to an internal 2.5V source for use
with open-drain outputs. The pull-up current diminishes to
zero above the logic threshold to protect voltage-sensitive
output devices. External pull-up resistors can augment the
pull-up current sources if case leakage into the driving
device is greater than 45µA.
Load-Line Regulation
Some microprocessor manufacturers require a precisely-
controlled output resistance. This dependence of output
voltage on load current is often termed “droop” or “load line”
regulation. By adding a well controlled output impedance,
the output voltage can effectively be level shifted in a
direction which works to achieve the load-line regulation
required by these manufacturers.
FIGURE 8. OUTPUT VOLTAGE AND LOAD-LINE
R
FB
EXTERNAL CIRCUIT
V
V
OUT
OUT
+
-
V
DROOP
C
R
REF
-
+
C
REGULATION WITH OFFSET ADJUSTMENT
R
C
REF
C
IDROOP
RGND
COMP
VDIFF
VSEN
DAC
REF
FB
ISL6307B INTERNAL CIRCUIT
I
AVG
DIFFERENTIAL
REMOTE-SENSE
AMPLIFIER
ERROR AMPLIFIER
+
-
+
-
V
COMP
March 9, 2006
DIFF
FN9225.0
, is