L5983TR STMicroelectronics, L5983TR Datasheet - Page 28

• Manufacturer Part Number: L5983TR
• Description: IC REG SW 1.5A STEPDOWN 8-VFQFPN
• Manufacturer: STMicroelectronics
• Type: Step-Down (Buck)r

Specifications of L5983TR

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 0.6 ~ 18 V
• Current - Output: 1.5A
• 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
• For Use With: 497-6386 - BOARD EVAL FOR L5983
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: 497-6860-2; L5983TR

Application information
5.6
28/43
For this device the path through the exposed pad is the one conducting the largest amount
of heat. The Rth
paragraph, is about 60 °/W.
Figure 16. Switching losses
Layout considerations
The PC board layout of the 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 is flowing through it. In order to minimize the EMI, this loop must be as
short as possible.
To filter the high frequency noise, a small capacitor can be added as close as possible to the
input voltage pin of the device.
The feedback pin (FB) connection to the external resistor divider is a high impedance node,
so the interferences can be minimized placing the routing of the 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.
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.
JA
, measured on the demonstration board described in the following
Doc ID 13005 Rev 7
L5983