L5981 STMicroelectronics, L5981 Datasheet - Page 19
L5981
Manufacturer Part Number
L5981
Description
IC REG SW STEP DOWN 1A 8-VFQFPN
Manufacturer
STMicroelectronics
Type
Step-Down (Buck)r
Datasheet
1.L5981TR.pdf
(37 pages)
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
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
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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