L6711TR STMicroelectronics, L6711TR Datasheet - Page 20

• Manufacturer Part Number: L6711TR
• Description: IC CTRLR 3PHASE VID/DACS 48-TQFP
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6711TR

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.8 ~ 1.55 V
• Current - Output: 2A
• Frequency - Switching: 150kHz
• Voltage - Input: 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 48-TQFP Exposed Pad, 48-eTQFP, 48-HTQFP, 48-VQFP
• Power - Output: 2.5W
• Output Voltage: 0.8 V to 1.581 V
• Output Current: 95 A
• Input Voltage: 13.8 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: 0 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5363-2; L6711TR

Current reading and current sharing control loop
7.2
20/50
50 A offset allows negative current reading, enabling the device to check for dangerous
returning current between the phases assuring the complete current equalization. From the
current information of each phase, information about the total current delivered (I
I
I
output in order to equalize the current carried by the three phases.
Figure 6.
Inductor current reading
Shorting CS_SEL pin to SGND, the current flowing trough each phase is read using the
voltage drop across the output inductor or across a sense resistor (R
internally converted into a current. The transconductance ratio is issued by the external
resistor Rg placed outside the chip between CSx- and CSx+ pins toward the reading points
(see
The current sense circuit always tracks the current sensed and still sources a constant 50 A
current 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 (See
7):
Where IP
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. Moreover, it is also important for the load transient response and to let
the system show resistive equivalent output impedance), it results:
I
50 A offset allows negative current reading, enabling the device to check for dangerous
returning current between the phases assuring the complete current equalization. From the
I
R
INFO1
INFO3
INFOx
CSx-
g RC
Figure 5
)/3 ) is taken. I
=
is the current information reproduced internally.
+ I
I
PHASEx
I
50 A
Cg
INFOx
INFO2
I
LSx
HASEx
Current reading across LS mosfet: timing (left) and circuit (right) for each
phase.
I
+
CSx-
right).
+ I
R
------ -
R
is the current carried by the relative phase.
T
L
g
TRACK
INFO3
=
⎛
⎜
⎜
⎜
INFOX
----------------------------------------------- -
1
50 A
+
) and the average current for each phase (I
s R
1
T
+
is then compared to I
+
SW
s
g R C
------- - I
Rg
R
L
------ -
R
L
L
PHASEx
Cg
⎞
⎟
⎟
⎟
⎠
I
PHASEx
=
50 A
AVG
+
I
I NFOx
to give the correction to the PWMx
50 A
I
CSx-
LGATEx
where
CSx+
CSx-
I
INFOx
AVG
Rg
Rg
SENSE
= (I
=
I
INFO1
PHASEx
) in its series and
I
PHASEx
+ I
DROOP
INFO2
------- -
Rg
R
L
Figure
L6711
+
=