L6713A STMicroelectronics, L6713A Datasheet - Page 32

• Manufacturer Part Number: L6713A
• Description: IC CTRLR 2/3PH W/DRIVERS 64-TQFP
• Manufacturer: STMicroelectronics

Specifications of L6713A

• Applications: Controller, Intel VR10, VR11, AMD CPU
• Voltage - Input: 12V
• Number Of Outputs: 3
• 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
• Output Current: 2 A
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Current reading and current sharing loop
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Current reading and current sharing loop
L6713A embeds a flexible, fully-differential current sense circuitry that is able to read across
inductor parasitic resistance or across a sense resistor placed in series to the inductor
element. The fully-differential current reading rejects noise and allows placing sensing
element in different locations without affecting the measurement's accuracy.
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
Figure 8.
Considering now to match the time constant between the inductor and the R-C filter applied
(Time constant mismatches cause the introduction of poles into the current reading network
causing instability. In addition, it is also important for the load transient response and to let
the system show resistive equivalent output impedance), it results:
Where I
------------ -
DCR
8):
PHASEx
INFOx
L
=
Current reading connections
is the current information reproduced internally.
R C
is the current carried by the relative phase.
⋅
⇒
I
CSx-
I
NO Bias
I
CSx-
CSx-
=I
INFOx
=
=
PHASEx
DCR
------------ - I
DCR
------------ -
Rg
Rg
CSx+
CSx-
⋅
⋅
1
------------------------------------------ - I ⋅
PHASEx
Inductor DCR Current Sense
+
1
s L
+
⋅
s R C
Rg
⋅
⁄
=
(
DCR
⋅
I
INFOx
R
I
PHASEx
Lx
)
C
⇒
PHASEx
DCR
x
I
INFOX
=
DCR
------------ - I
Rg
⋅
PHASEx
(See
L6713A