L6728 STMicroelectronics, L6728 Datasheet - Page 19

• Manufacturer Part Number: L6728
• Description: IC PWM CTLR 1PH PWRGOOD 10-DFN
• Manufacturer: STMicroelectronics

Specifications of L6728

• Pwm Type: Voltage Mode
• Number Of Outputs: 1
• Frequency - Max: 330kHz
• Duty Cycle: 80%
• Voltage - Supply: 4.5 V ~ 12 V
• Buck: Yes
• Boost: No
• Flyback: No
• Inverting: No
• Doubler: No
• Divider: No
• Cuk: No
• Isolated: No
• Operating Temperature: -40°C ~ 125°C
• Package / Case: 10-DFN
• Frequency-max: 330kHz
• Output Voltage: 0.8 V
• Output Current: 30 A
• Input Voltage: 1.5 V to 13.2 V
• Mounting Style: SMD/SMT
• Maximum Operating Temperature: + 125 C
• Minimum Operating Temperature: - 40 C
• For Use With: 497-8228 - BOARD EVALUATION W/L6728497-6418 - BOARD EVAL BASED ON L6728
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

L6728
11
11.1
Application information
Inductor design
The inductance value is defined by a compromise between the dynamic response time, the
efficiency, the cost and the size. The inductor has to be calculated to maintain the ripple
current (ΔI
value can be calculated with the following relationship:
Where F
voltage.
inductor, with V
Increasing the value of the inductance reduces the current ripple but, at the same time,
increases the converter response time to a dynamic load change. The response time is the
time required by the inductor to change its current from initial to final value. Until the inductor
has not finished its charging time, the output current is supplied by the output capacitors.
Minimizing the response time can minimize the output capacitance required. If the
compensation network is well designed, during a load variation the device is able to set a
duty cycle value very different (0 % or 80 %) from steady state one. When this condition is
reached, the response time is limited by the time required to change the inductor current.
Figure 9.
L
=
V
----------------------------- -
F
IN
SW
–
Figure 9
SW
V
⋅
L
ΔI
OUT
) between 20 % and 30 % of the maximum output current (typ). The inductance
is the switching frequency, V
Inductor current ripple vs output voltage
L
⋅
IN
V
--------------
V
shows the ripple current vs. the output voltage for different values of the
OUT
= 5 V and V
IN
IN
= 12 V.
IN
is the input voltage and V
Application information
OUT
is the output
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