E-L6919ETR STMicroelectronics, E-L6919ETR Datasheet - Page 11

• Manufacturer Part Number: E-L6919ETR
• Description: IC CTRLR 5BIT PROG 2PHASE 28SOIC
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of E-L6919ETR

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 0.8 ~ 1.55 V
• Current - Output: 2A
• Frequency - Switching: 150kHz
• Voltage - Input: 5 ~ 12 V
• Operating Temperature: -40°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC (7.5mm Width)
• Power - Output: 2W
• Mounting Style: SMD/SMT
• Operating Supply Voltage: 6.5 V
• Maximum Operating Temperature: 85 C
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-4592-2

Figure 4. Current Reading Timing (Left) and Circuit (Right)
Where R
resistor used between ISENx and PGNDSx pins toward the reading points; I
=I
The transconductance resistor Rg can be designed in order to have current information of 25 A per phase at
of the total delivered maximum current, results:
Since the device senses the output current across the low-side mosfets (or across a sense resistors in series
with them) the device limits the bottom of the inductor current triangular waveform: an over current is detected
when the current flowing into the sense element is greater than I
This linear dependence has a value at zero load of 0.80·T and at maximum current of 0.40·T typical and results
in two different behaviors of the device:
phase and, in particular, the current measured in the middle of the oscillator period
The current information reproduced internally is represented by the second term of the previous equation as
follow:
Since the current is read in differential mode, also negative current information is kept; this allow the device to
check for dangerous returning current between the two phases assuring the complete equalization between the
phase's currents. From the current information of each phase, information about the total current delivered (I
pared to I
full nominal load; the over current intervention threshold is set at 140% of the nominal (I
to the above relationship, the over current threshold (I
Introducing now the maximum ON time dependence with the delivered current (where T is the switching period
T=1/f
Total current
information
INFO1
I
I
LS1
LS2
T
SW
ON,MAX
+I
):
SENSE
AVG
INFO2
to give the correction to the PWM output in order to equalize the current carried by the two phases.
) and the average current for each phase (I
=
is an external sense resistor or the rds,on of the low side mosfet and Rg is the transconductance
0.80
–
I
FB
I
Track & Hold
OCPx
5.73 k
=
35 A Rg
-------------------------- -
R
T
I
INFO x
S ENSE
=
0.80
=
–
R
----------------------------------------------


SENSE
R
--------------------- - I
OCPx
SENSE
Rg
AVG
Rg
) for each phase, which has to be placed at one half
R
g
I
=(I
=
PHASE
OCPx
INFO1
I
------------------------------------------ -
OUT
OCP x
PGNDSX
LGATEX
(I
35 A
+I
5.73k
INFOx
ISENX
INFO2
R
SE NSE
PHASE


> 35 A).
)/2 ) is taken. I
T
is the current carried by each



0.80 T I
0.40 T I
INFOx
50 A
I
ISENx
Rg
Rg
= 35 A). According
INFOX
F B
F B
=
=
is then com-
0 A
7 0 A
L6919E
11/33
FB