HIP6304 Intersil Corporation, HIP6304 Datasheet - Page 9

• Manufacturer Part Number: HIP6304
• Description: Microprocessor CORE Voltage Regulator Multi-Phase Buck PWM Controller
• Manufacturer: Intersil Corporation

Current Sensing and Balancing
Overview
The HIP6304 samples the on-state voltage drop across each
synchronous rectifier FET, Q2, as an indication of the
inductor current in that phase, see Figure 7. Neglecting AC
effects (to be discussed later), the voltage drop across Q2 is
simply r
inductor current, is 1/2 of the total current (I
The voltage at Q2’s drain, the PHASE node, is applied to the
R
ISEN pin. This pin is held at virtual ground, so the current
through R
The I
following functions:
Over-Current, Selecting R
The current detected through the R
with the current detected in the other channel. The averaged
current is compared with a trimmed, internally generated
current, and used to detect an over-current condition.
The nominal current through the R
50 A at full output load current, and the nominal trip point for
1. Detection of an over-current condition
2. Reduce the regulator output voltage with increasing load
3. Balance the I
ISEN
current (droop)
ISEN
FB
resistor to develop the I
DS(ON)
ISEN
current provides information to perform the
CURRENT
TO OVER
REFERENCE
AMPLIFIER
FIGURE 7. SIMPLIFIED FUNCTIONAL BLOCK DIAGRAM SHOWING CURRENT AND VOLTAGE SAMPLING
is I
R
(Q2) x inductor current (I
ERROR
+
-
TRIP
FB
L
DAC
R
L
currents in the two phases
IN
x r
C
COMPARATOR
DS(ON)
c
TO OTHER
CHANNEL
COMP
9
(Q2) / R
GENERATOR
ISEN
ISEN
SAWTOOTH
CORRECTION
+
+
-
ISEN
ISEN
current to the HIP6304
DIFFERENCE
-
ISEN
resistor should be
L
resistor is averaged
REFERENCE
). Note that I
-
.
LT
+
).
AVERAGING
COMPARATOR
+
-
L
, the
HIP6304
CURRENT
SENSING
CURRENT
SENSING
FROM
OTHER
CHANNEL
CIRCUIT
HIP6304
PWM
over-current detection is 165% of that value, or 82.5 A.
Therefore, R
For a full load of 25A per phase, and an r
4m , R
The over-current trip point would be 165% of 25A, or ~ 41A
per phase. The R
over-current trip point, but it is suggested to stay within 25%
of nominal.
Droop, Selection of R
The average of the currents detected through the R
resistors is also steered to the FB pin. There is no DC return
path connected to the FB pin except for R
current creates a voltage drop across R
the apparent V
causing the system to decrease V
the FB pin. This is the desired “droop” voltage used to maintain
V
With a high dv/dt load transient, typical of high performance
microprocessors, the largest deviations in output voltage
occur at the leading and trailing edges of the load transient. In
order to fully utilize the output-voltage tolerance range, the
output voltage is positioned in the upper half of the range
when the output is unloaded and in the lower half of the range
when the controller is under full load. This droop
compensation allows larger transient voltage deviations and
thus reduces the size and cost of the output filter components.
CORE
PWM
ISEN
within limits under transient conditions.
I
SEN
ISEN
= 2k .
CORE
ONLY ONE OUTPUT
HIP6601
ISEN
= I
L
voltage with increasing load current,
STAGE SHOWN
R
x r
value can be adjusted to change the
ISEN
DS(ON)
IN
INDUCTOR
Q2
CURRENT
CHANNEL
V
IN
OTHER
FROM
Q1
CORE
(Q2) / 50 A.
PHASE
L
I
IN
01
L
to maintain balance at
IN
. This drop increases
DS(ON)
, so the average
V
CORE
(Q2) of
ISEN