MICRF620TR datasheet(17/18 Pages) MICREL

17 / 18 page

Micrel, Inc.

MICRF620

December 2005

M9999-120205

Application Circuit Illustration

Figure 10. Circuit illustration of MICRF620, LDO and MCU

Figure 10. shows a typical set-up with the MICRF620, a

Low-Drop-Out voltage regulator (LDO)

and a micro-

controller (MCU). When the MICRF620 and the MCU runs

on the same power supply (min 2.0, max. 2.5V), the IO

can be connected directly to the MCU. If the MCU needs a

higher VDD than the max. specified VDD of the MICRF620

(2.5V), voltage dividers need to be added on the IO lines

not to override the max. input voltage.

Figure 11 shows a recommended voltage divider circuit for

a MCU running at 3.0V and the MICRF620 at 2.5V.

3k3

18k

3k3

18k

3k3

18k

15k

MICRF6xx

MCU

SCLK

DATAIXO

DATACLK

RSSI

SCLK

DATAIXO

DATACLK

RSSI

Figure 11. How to connect MICRF620 (2.5V) and MCU (3.0V)

Assembling the MICRF620

Recommended Reflow Temperature Profile

When the MICRF620 module is being automatically

assembled to a PCB, care must be taken not to expose

the module for temperature above the maximum specified.

Figure 12 shows the recommended reflow temperature

profile.

Figure 12. Recommended Reflow Temperature Reflow

Shock/Vibration during Reflow

The module has several components inside which are

assembled in a reflow process. These components may

reflow again when the module is assembled onto a PCB. It

is therefore important that the module is not subjected to

any mechanical shock or vibration during this process.

Handassembling the MICRF620

It is recommended to use solder paste also during hand

assembling of the module. Because of the module ground

pad on the bottom side, the module will be assembled

most efficient if the heat is being subjected to the bottom

side of the PCB. The heat will be transferred trough the

PCB due the ground vias under the module (see Layout

Considerations). In addition, it is recommended to use a

solder tip on the signal and power pads, to make sure the

solder points are properly melted.

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