L6714 STMicroelectronics, L6714 Datasheet - Page 33

• Manufacturer Part Number: L6714
• Description: IC CTRLR 4PH W/DRIVERS 64-TQFP
• Manufacturer: STMicroelectronics

Specifications of L6714

• Applications: Controller, Intel VR10, VR11, AMD CPU
• Voltage - Input: 12V
• Number Of Outputs: 4
• Voltage - Output: 0.3 ~ 1.6 V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 64-TQFP Exposed Pad, 64-eTQFP, 64-HTQFP, 64-VQFP
• Mounting Style: SMD/SMT
• Case: QFP
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

L6714
10.1
10.2
Low side current reading
When reading current across LS, the current flowing trough each phase is read using the
voltage drop across the low side MOSFET R
it is internally converted into a current. The trans-conductance ratio is issued by the external
resistor Rg placed outside the chip between CSx- and CSx+ pins toward the reading points.
The current sense circuit tracks the current information for a time T
middle of the LS conduction time and holds the tracked information during the rest of the
period.
L6714 sources a constant 25 A bias current from the CSx+ pin: the current reading circuitry
uses this pin as a reference and the reaction keeps the CSx- pin to this voltage during the
reading time (an internal clamp keeps CSx+ and CSx- at the same voltage sinking from the
CSx- pin the necessary current during the hold time; this is needed to avoid absolute
maximum rating overcome on CSx- pin). The current that flows from the CSx- pin is then
given by
where R
resistor used between CSx- and CSx+ pins toward the reading points; I
carried by the relative phase and I
internally.
25 A offset allows negative current reading, enabling the device to check for dangerous
returning current between the phases assuring the complete current equalization.
Inductor current reading
When reading current across the inductor DCR, the current flowing trough each phase is
read using the voltage drop across the output inductor or across a sense resistor in its
series and internally converted into a current. The trans-conductance ratio is issued by the
external resistor Rg placed outside the chip between CSx- pin toward the reading points.
The current sense circuit always tracks the current information, no bias current is sourced
from the CSx+ pin: this pin is used as a reference keeping the CSx- pin to this voltage. To
correctly reproduce the inductor current an R-C filtering network must be introduced in
parallel to the sensing element.
The current that flows from the CSx- pin is then given by the following equation
Figure
Where I
9):
PHASEx
dsON
(See Figure
is the ON resistance of the low side MOSFET and Rg is the trans-conductance
is the current carried by the relative phase.
9):
I
CSx-
=
I
CSx-
25 A
=
INFOx
+
------- -
Rg
R
R
---------------- -
L
dsON
Rg
is the current information signal reproduced
1
-------------------------------------
1
+
+
s
dsON
s
I
PHASEx
Current reading and current sharing loop
L
R
or across a sense resistor in its series and
R
C
L
=
I
25 A
PHASEx
+
I
INFOx
TRACK
PHASEx
centered in the
is the current
(See
33/70