L5987TR STMicroelectronics, L5987TR Datasheet - Page 22

• Manufacturer Part Number: L5987TR
• Description: IC REG SW 3A STEPDOWN 8-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L5987TR

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 18 V
• Current - Output: 3A
• Frequency - Switching: 250kHz
• Voltage - Input: 2.9 ~ 18 V
• Operating Temperature: -40°C ~ 150°C
• Mounting Type: Surface Mount
• Package / Case: 8-VFQFN, 8-VFQFPN
• Power - Output: 1.5W
• Output Voltage: 0.6 V
• Output Current: 3 A
• Output Power: 1.5 W
• Input Voltage: 2.9 V to 18 V
• Switching Frequency: 250 KHz
• Mounting Style: SMD/SMT
• Duty Cycle (max): 100 %
• For Use With: 497-8369 - BOARD EVALUATION FOR L5987
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-8494-2

Application information
22/41
Equation 21
Figure 11. Type III compensation network
In
and the open loop gain (G
Figure 12. 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 12
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 kΩ and 5 kΩ.
Doc ID 14972 Rev 3
f
(f) = G
P1
=
----------------------------- -
2π R
PW0
⋅
1
3
· G
⋅
C
LC
3
,
(f) · G
f
P2
TYPEIII
=
------------------------------------------- -
2π R
⋅
(f)) are drawn.
4
1
⋅
------------------- -
C
C
4
4
+
⋅
C
C
5
5
PW0
· G
LC
L5987
(f))