L6911C View Datasheet(PDF) - STMicroelectronics
Part Name
Description
MFG CO.
'L6911C' PDF : 20 Pages View PDF
L6911C
Inductor selection
Since the maximum output current is equal to 14A, to have a 30% ripple (4A) in worst case a 3µH inductor has
been chosen. So the ripple is 4.1A @ 3.5V with VIN=12V and 1.7A @ 3.5V with VIN = 5V.
In worst case the peak is equal to 18.1A.
Output Capacitor
In the demo ten Sanyo capacitors, model 6MV1000GX are used, with a maximum ESR equal to 69mΩ. There-
fore, the resultant ESR is 69mΩ/10 = 1.9mΩ. For a load transient of 14A in worst case the drop results:
∆Vout = 14 * 0.00069 = 96.6mV
The voltage drop due to the capacitor discharge during load transient, considering that the maximum duty cycle
is equal to 100% results in 13mV with 2.5V of programmed output.
Input Capacitor
For IOUT = 14A and D = 0.5 (worst case for input ripple current), Irms is equal to 7A. Five Sanyo electrolytic
capacitors 25MV330GX, with a maximum ESR equal to 69mΩ, are chosen to sustain the ripple. Therefore, the
resultant ESR is equal to 69mΩ/5 = 13.8mΩ. So the losses in worst case are:
P = ESR ⋅ Ir2ms = 670 mW
Over-Current Protection
Substituting the demo board parameters in the relationship reported in the relative section, (IOCSMIN = 170µA;
IP = 19A; RDSONMAX = 9mΩ) it results that ROCS = 1kΩ.
Part List
R2
R3, R7
R4
R5, R8
R9
R12
R13, R14
C1, C2…C5
C6, C7…C15
C16, C17, C24, C25
C18
C19
C20
C21, C22
C23
L1
L2
U1
Q1, Q2…Q6
D1
D2
F1
499k
1k
20
20k
15k
1K
0
330µ
1000µ
100n
2.2n
8.2n
82n
1µ
1n
1.5µ
3µ
L6911C
STS12NF30L
1N4148
STPS3L25U
251015A-15°
1%
1%
SANYO – 25MV330GX
SANYO – 6MV1000GX
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
Ceramic
T44-52 Core, 7T-18AWG
T50-52B Core, 10T-16AWG
STMicroelectronics
STMicroelectronics
STMicroelectronics
STMicroelectronics
Littlefuse
SMD 0805
SMD 0805
SMD 0805
SMD 0805
SMD 0805
SMD 0805
SMD 0805
Radial 8x20mm
Radial 8x20mm
SMD 0805
SMD 0805
SMD 0805
SMD 0805
SMD 1206
SMD 0805
SO20
SO8
SOT23
SMB
AXIAL
16/20
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