E-L6911C STMicroelectronics, E-L6911C Datasheet - Page 16

• Manufacturer Part Number: E-L6911C
• Description: IC CTRLR 5BIT PROGR STPDN 20SOIC
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of E-L6911C

• Internal Switch(s): No
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.3 ~ 3.5 V
• Current - Output: 1.3A
• Frequency - Switching: 200kHz
• Voltage - Input: 5 ~ 12 V
• Operating Temperature: -40°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 20-SOIC (7.5mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

L6911C
Inductor selection
Since the maximum output current is equal to 14A, to have a 30% ripple (4A) in worst case a 3 H inductor has
been chosen. So the ripple is 4.1A @ 3.5V with V
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 69m . There-
fore, the resultant ESR is 69m /10 = 1.9m . For a load transient of 14A in worst case the drop results:
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 I
capacitors 25MV330GX, with a maximum ESR equal to 69m , are chosen to sustain the ripple. Therefore, the
resultant ESR is equal to 69m /5 = 13.8m . So the losses in worst case are:
Over-Current Protection
Substituting the demo board parameters in the relationship reported in the relative section, (I
I
Part List
16/20
P
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
= 19A; R
OUT
= 14A and D = 0.5 (worst case for input ripple current), Irms is equal to 7A. Five Sanyo electrolytic
DSONMAX
= 9m ) it results that R
499k
1k
20
20k
15k
1K
0
330
1000
100n
2.2n
8.2n
82n
1
1n
1.5
3
L6911C
STS12NF30L
1N4148
STPS3L25U
251015A-15°
P
Vout = 14 * 0.00069 = 96.6mV
=
OCS
ESR I
= 1k .
IN
=12V and 1.7A @ 3.5V with V
2
rm s
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
=
670 mW
IN
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
= 5V.
OCSMIN
= 170 A;