L5985 STMicroelectronics, L5985 Datasheet - Page 27
L5985
Manufacturer Part Number
L5985
Description
IC REG SW STEP DOWN 2A 8-VFQFPN
Manufacturer
STMicroelectronics
Type
Step-Down (Buck)r
Datasheet
1.L5985TR.pdf
(37 pages)
Specifications of L5985
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 %
Low Dropout Operation
100% duty cycle
For Use With
497-6387 - BOARD EVAL FOR L5985
Lead Free Status / RoHS Status
Lead free / RoHS Compliant
Available stocks
Company
Part Number
Manufacturer
Quantity
Price
Company:
Part Number:
L5985
Manufacturer:
STMicroelectronics
Quantity:
1 035
Part Number:
L5985
Manufacturer:
ST
Quantity:
20 000
Part Number:
L5985TR
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ST
Quantity:
20 000
Part Number:
L5985TR-LF4
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20 000
L5985
5.6
Figure 16. Switching losses
Layout considerations
The PC board layout of switching DC/DC regulator is very important to minimize the noise
injected in high impedance nodes and interferences generated by the high switching current
loops.
In a step-down converter the input loop (including the input capacitor, the power MOSFET
and the free wheeling diode) is the most critical one. This is due to the fact that the high
value pulsed current are flowing through it. In order to minimize the EMI, this loop has to be
as short as possible.
The feedback pin (FB) connection to external resistor divider is a high impedance node, so
the interferences can be minimized placing the routing of feedback node as far as possible
from the high current paths. To reduce the pick up noise the resistor divider has to be placed
very close to the device. To filter the high frequency noise, a small capacitor (100 nF) can be
added as close as possible to the input voltage pin of the device.
Thanks to the exposed pad of the device, the ground plane helps to reduce the thermal
resistance junction to ambient; so a large ground plane enhances the thermal performance
of the converter allowing high power conversion.
In
Figure 17
a layout example is shown.
Doc ID 13006 Rev 5
Application information
27/37