L5985TR STMicroelectronics, L5985TR Datasheet - Page 18

• Manufacturer Part Number: L5985TR
• Description: IC REG SW 2A STEP DOWN 8-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L5985TR

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 18 V
• Current - Output: 2A
• 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: 2 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 %
• For Use With: 497-6387 - BOARD EVAL FOR L5985
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6861-2; L5985TR

Application information
18/37
The transfer function on the LC filter is given by:
Equation 13
where:
Equation 14
Equation 15
As seen in
following paragraph the guidelines to select the Type II and Type III compensation network
are illustrated.
Figure 9.
V
V
FB
FB
REF
REF
Chapter 4.3
Error amplifier, PWM modulator and LC output filter
E/A
E/A
f
Q
LC
=
=
----------------------------------------------------------------------------------------- -
----------------------------------------------------------------------- -
2π
V
V
two different kind of network can compensate the loop. In the two
R
S
S
COMP
COMP
OUT
⋅
L
L C
G
+
⋅
⋅
LC
L C
C
Doc ID 13006 Rev 5
OUT
⋅
s ( )
OUT
G
G
1
PW0
PW0
OUT
=
⋅
⋅
R
------------------------------------------------------------------------ -
1
OUT
PWM
PWM
1
⋅
+
(
+
R
----------------------------
2π Q f ⋅
-------------- -
R
OUT
ESR
⋅
OUT
E SR
1
⋅
s
+
+
,
------------------------- -
2π f
ESR
LC
⋅
f
s
+
zESR
zESR
)
⎛
⎝
,
------------------ -
2π f
V
V
CC
CC
s
=
⋅
OUT
OUT
LC
------------------------------------------- -
2π ESR C
R
⎞
⎠
OUT
⋅
2
G
G
1
=
LC
LC
⋅
V
--------------
I
L
L
OUT
OUT
OUT
ESR
ESR
C
C
OUT
OUT
L5985