E-L6919ETR STMicroelectronics, E-L6919ETR Datasheet - Page 19

• 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

necessary) to sense the current. The current sharing error is internally dominated by the voltage offset of Tran
conductance differential amplifier; considering a voltage offset equal to 2mV across the sense resistor, the cur-
rent reading error is given by the following equation:
Where I
For R
Rsense mismatches.
Figure 14. Current Sharing Control Loop
Average Current Mode (ACM) Control Loop
The average current mode control loop is reported in figure 15. The current information I
–
– Z
– Z
– Z
– A(s) is the error amplifier gain;
–
Removing the dependence from the Error Amplifier gain, so assuming this gain high enough, the control loop
gain results:
pin flows into RFB implementing the dependence of the output voltage from the read current.
The ACM control loop gain results (obtained opening the loop after the COMP pin):
Where:
load Ro;
and has a typical value of 3V
R
PWM
P
F
L
DROOP
(s) is the parallel of the two inductor impedance;
(s) is the impedance resulting by the parallel of the output capacitor (and its ESR) and the applied
(s) is the compensation network impedance;
SENSE
READ
=
= 4m and I
4
-- -
5
=
is the difference between one phase current and the ideal current (I
------------------ -
R
------------------ - R
V
s en se
R
V
O SC
g
IN
G
· is the ACM PWM transfer function where V
MAX
LO O P
FB
= 40A the current sharing error is equal to 2.5%, neglecting errors due to Rg and
COMP
is the equivalent output resistance determined by the droop function;
s
+
+
=
--------------------------------------------------------------------------------------------------------------------
Z
------------------- -
P
PWM1
PWM2
I
I
M AX
RE AD
1/5
1/5
s
PWM Z
+
Z
=
L
D02IN1393
s
--------------------------------------- -
R
CORRECTION
DUTY CYCLE
F
CURRENT
SHARING
SENSE
s
2mV
Z
-------------- -
A s
F
R
s
DROOP
I
M AX
+
I
I
INFO2
INFO1


L 1
L 2
1
+
+
----------- -
A s
OSC
Z
1
V
P
OUT


s
is the oscillator ramp amplitude
R
FB
MAX
/2).
FB
sourced by the FB
L6919E
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