L6727 STMicroelectronics, L6727 Datasheet - Page 20

• Manufacturer Part Number: L6727
• Description: IC PWM CTLR SGL PHASE SO-8
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L6727

• Internal Switch(s): No
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: Adj to 0.8V
• Frequency - Switching: 300kHz
• Voltage - Input: 1.5 ~ 12 V
• Operating Temperature: -20°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Output Current: 1.5 A
• Input Voltage: - 0.3 V to + 15 V
• Switching Frequency: 300 KHz
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 80 %
• For Use With: 497-8266 - BOARD EVAL BASED ON L6727497-6258 - BOARD EVAL 1PH STPDWN CONV L6727
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Current - Output: -
• Power - Output: -
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

Application information
10
10.1
20/34
Application information
Output inductor
Inductor value is defined by a compromise between dynamic response, ripple, efficiency,
cost and size. Usually, inductance is calculated to maintain inductor ripple current (ΔI
between 20 % and 30 % of maximum output current. Given the switching frequency (F
the input voltage (V
inductance can be calculated as follows:
Figure 1
V
Increasing inductance reduces inductor ripple current (and output voltage ripple
accordingly) but, at the same time, increases the converter response time to load transients.
Higher inductance means that the inductor needs more time to change its current from initial
to final value. Until the inductor has not finished its charging, the additional output current is
supplied by output capacitors. Minimizing the response time lead to minimize the output
capacitance required. If the compensation network is designed with high bandwidth, during
an heavy load transient the device is able to saturate duty cycle (0 % or 80 %). When this
condition is reached, the response time is limited only by the time required to charge the
inductor.
Figure 10. Inductor current ripple vs output voltage
L
IN
=
= 5 V and V
V
----------------------------- -
F
IN
SW
–
shows the ripple current vs. the output voltage for different inductance, with
V
⋅
ΔI
OUT
L
⋅
IN
V
--------------
V
OUT
= 12 V.
IN
IN
), the output voltage (V
Doc ID 12933 Rev 4
OUT
) and the desired ripple current (ΔI
L
),
L
L6727
)
SW
),