hip6301 Intersil Corporation, hip6301 Datasheet - Page 12

• Manufacturer Part Number: hip6301
• Description: Microprocessor Core Voltage Regulator Multiphase Buck Pwm Controller
• Manufacturer: Intersil Corporation

Current Sensing and Balancing
Overview
The HIP6301 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 either 1/2, 1/3, or 1/4 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:
1. Detection of an overcurrent condition
2. Reduce the regulator output voltage with increasing load
3. Balance the I
LT
ISEN
), depending on how many phases are in use.
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
(Q2) x inductor current (I
is
R
ERROR
+
-
TRIP
FB
L
DAC
I
R
L
currents in multiple channels
IN
=
C
COMPARATOR
r
----------------------------------- -
c
DS ON
CHANNELS
TO OTHER
R
(
ISEN
COMP
12
)
GENERATOR
ISEN
(
SAWTOOTH
CORRECTION
Q2
+
+
-
)
current to the HIP6301
DIFFERENCE
-
L
). Note that I
REFERENCE
-
+
AVERAGING
COMPARATOR
+
-
L
, the
HIP6301
HIP6301
HIP6301
CURRENT
SENSING
CURRENT
SENSING
FROM
OTHER
CHANNELS
CIRCUIT
PWM
Overcurrent, Selecting R
The current detected through the R
with the current(s) detected in the other 1, 2, or 3 channels.
The averaged current is compared with a trimmed, internally
generated current, and used to detect an overcurrent
condition.
The nominal current through the R
50µA at full output load current, and the nominal trip point for
overcurrent detection is 165% of that value, or 82.5µA
Therefore,
For a full load of 25A per phase, and an r
4mΩ, R
The overcurrent trip point would be 165% of 25A, or ~ 41A
per phase. The R
overcurrent 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
PWM
ISEN
I
SEN
R
ISEN
= 2kΩ.
HIP6601B
ONLY ONE OUTPUT
ISEN
=
( )r
--------------------------------------------- -
STAGE SHOWN
I
R
L
ISEN
value can be adjusted to change the
DS ON
CURRENT(S)
IN
50µA
CHANNELS
INDUCTOR
(
Q2
V
ISEN
IN
OTHER
FROM
)
(
Q1
Q2
ISEN
PHASE
ISEN
)
.
L
I
01
L
resistor should be
resistor is averaged
DS(ON)
IN
, so the average
December 27, 2004
V
CORE
(Q2) of
ISEN
FN4765.6