L5983 STMicroelectronics, L5983 Datasheet - Page 16

• Manufacturer Part Number: L5983
• Description: IC REG SW STEP DOWN 1.5A 8VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L5983

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 18 V
• Current - Output: 1.5A
• Frequency - Switching: 250kHz ~ 1MHz
• Voltage - Input: 2.9 ~ 18 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-VFQFN, 8-VFQFPN
• Power - Output: 1.5W
• Output Voltage: 3 V
• Output Current: 1.5 A
• Input Voltage: 2.9 V to 18 V
• Switching Frequency: 220 KHz to 275 KHz
• Operating Temperature Range: - 40 C to + 150 C
• Mounting Style: SMD/SMT
• Duty Cycle (max): 100 %
• Low Dropout Operation: 100 % duty cycle
• For Use With: 497-6386 - BOARD EVAL FOR L5983
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Application information
5.2
16/43
Inductor selection
The inductance value fixes the current ripple flowing through the output capacitor. So the
minimum inductance value, in order to have the expected current ripple, must be selected.
The rule to fix the current ripple value is to have a ripple at 20 %-40 % of the output current.
The inductance value can be calculated by the following equation:
Equation 6
where T
time of the external diode (in CCM, F
fixed V
section to calculate minimum duty). So fixing ΔI
current, the minimum inductance value can be calculated as:
Equation 7
where F
For example, for V
inductance value to have ΔI
The peak current through the inductor is given by:
Equation 8
So if the inductor value decreases, the peak current (which must be lower than the current
limit of the device) increases. The higher the inductor value, the higher the average output
current that can be delivered, without reaching the current limit.
In
Table 7.
Table 7
Manufacturer
Coiltronics
OUT
SUMIDA
Coilcraft
ON
SW
Wurth
, is obtained at maximum T
some inductor part numbers are listed.
BI
is the conduction time of the internal high side switch and T
is the switching frequency, 1/(T
Inductors
OUT
= 3.3 V, V
CDRH8D28/HP
ΔI
L
CDRH8D28
= 30 % of I
L
MSS1038
MSS7341
Doc ID 13005 Rev 7
HM76-3
UP2.8B
Series
=
L
CD1
IN
PD
MIN
V
----------------------------- - T
= 12 V, I
IN
SW
–
OFF
=
L
I
V
L PK
,
V
--------------------------- -
O
= 1 / (T
OUT
OUT
that is at minimum duty cycle (see previous
ΔI
is about 21 μH.
ON
O
MAX
=
⋅
= 1.5 A and F
+
+ T
I
ON
O
ON
V
L
Inductor value (μH)
+
F
= 20 % to 40 % of the maximum output
OFF
⋅
ΔI
------- -
=
+ T
2
1 D
---------------------- -
L
V
-------------- T
–
).
3.3 to 6.8
3.3 to 6.2
F
4.7 to 10
4.7 to 10
OFF
15 to 18
15 to 22
15 to 33
15 to 22
OUT
SW
L
MIN
)). The maximum current ripple, at
⋅
SW
OFF
= 250 kHz, the minimum
Saturation current (A)
OFF
is the conduction
2.75 to 4.2
3.2 to 3.6
2.5 to 3.5
2.7 to 3.9
2.5 to 3.7
2.5 to 2.8
2.9 to 3.6
2.5 to 3.4
L5983