L6722TR STMicroelectronics, L6722TR Datasheet - Page 19

• Manufacturer Part Number: L6722TR
• Description: IC BUCK ADJ 2A TRPL 36VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6722TR

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 3
• Voltage - Output: Adj to 0.8V
• Current - Output: 2A
• Frequency - Switching: 100kHz
• Voltage - Input: 12V
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 36-VFQFN, 36-VFQFPN
• Power - Output: 3.5W
• Operating Temperature Range: - 40 C to + 125 C
• Mounting Style: SMD/SMT
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-5904-2

L6722
Warning:
Caution:
Time constant matching between the inductor (L / DCR) and the current reading filter
(
avoiding over and/or under shoot of the output voltage as a consequence of a load transient. In
fact, considering the scheme reported on
By applying the time constant matching concept, it results:
The device forces I
R
then given by (Offset disabled):
Where R
The whole power supply can be then represented by a "real" voltage generator with an
equivalent output resistance R
R
Droop function is operational for output voltages up to 1.8V.
Droop function is optional, in case it is not desired, the Current Sense circuit can be tricked so
that the device always read a null current. To do this, it is enough connecting CS+ directly to the
output voltage leaving CS- unconnected. The reaction will keep CS+ and CS- at the same
voltage, always reading a null current and also assuring the FB disconnection protection to be
effective. To aovid setting the FB-disconnection protection, it is also suggested to connect CS+
to local-V
To disable also the FB disconnection protection, CS+ can be directly connected to VSEN or
SGND.
Figure 9.
R
PHASE1
PHASE2
PHASE3
FB
FB
PH
implementing the load regulation dependence. The output characteristic vs. load current is
resistor can be then designed according to the R
⋅
C
OUT
PH
LL
OUT
CS+
) is required to implement a real equivalent output impedance of the system so
is the resulting load-line resistance implemented by the system.
Droop function current reading network
=
through the same resistor divider used as external divider (See
C
L1
L2
L3
Droop Function Enabled
PH
VID R
DROOP
R
DCR1
DCR2
DCR3
D
–
CS-
I
CS
FB
------------ -
DCR
x 3
= I
V
S
⋅
OUT
L
I
DROOP
CS
=
I
DROOP
LL
I
----------- -
=
x 3, proportional to the read current, into the feedback resistor
OUT
FB
and a voltage value of VID.
3
R
R
----------------------------- -
F
R
FB
PH
⋅
R
C
=
F
------------------------------------------------------------ -
1
⋅
FB
3
VID R
+
C
COMP
Figure
1
s
=
PH
+
⋅
–
R
s
=>
R
LL
⋅
PH
FB
9, it is possible to observe that:
I
PHASE1
PHASE2
PHASE3
⋅
L
CS
⋅
⁄
⋅
------------ -
DCR
R
LL
DCR
C
=
DCR
------------ -
D
R
PH
specifications as follow:
I
----------- -
D
OUT
3
⁄
CS+
⋅
3
⋅
I
OUT
⋅
Droop Function Disabled
L1
L2
L3
DCR
------------ -
DC
--------
R
R
D
D
=
DCR1
DCR2
DCR3
7 Output voltage positioning
VID R
R
R
CS-
1
2
I
CS
x 3
–
V
OUT
I
DROOP
Figure
LL
⋅
FB
R
F
I
R
OU
1).
FB
C
F
19/34
COMP