L5981 STMicroelectronics, L5981 Datasheet - Page 19

• Manufacturer Part Number: L5981
• Description: IC REG SW STEP DOWN 1A 8-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L5981

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 18 V
• Current - Output: 1A
• 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 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: 497-6385 - BOARD EVAL FOR L5981
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

L5981
Equation 17
Figure 10. Type III compensation network
In
and the open loop gain (G
Figure 11. Open loop gain: module Bode diagram
The guidelines for positioning the poles and the zeroes and for calculating the component
values can be summarized as follow:
1.
2.
Figure 11
Choose a value for R
Choose a gain (R
the Bode diagram of the PWM and LC filter transfer function (G
f
P0
4
/R
=
0
1
1
LOOP
) in order to have the required bandwidth (BW), that means:
,
, usually between 1 k and 5 k.
Doc ID 13004 Rev 6
f
(f)=G
P1
=
----------------------------- -
2π R
PW0
⋅
1
· G
3
⋅
LC
C
3
(f) · G
,
f
P2
TYPEIII
=
------------------------------------------- -
2π R
(f)) are drawn.
⋅
4
1
⋅
------------------- -
C
C
4
4
Application information
+
⋅
C
C
5
5
PW0
· G
LC
(f))
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