User's Manual

WM620 Hardware User Guide V1.1

Table 2-2 Keep-alive capacitor values vs. SMPL timer settings

SMPL timer setting

Capacitor value

Capacitor package (X7R)

0.5 sec

1.5 µF

0805

1.0 sec

3.3 µF

0805

1.5 sec

4.7 µF

0805

2.0 sec

6.8 µF

1206

2.1.3 Power Supply Output

The VDD_1.8V and VDD_2.6V pins are two linear regulator outputs. These two pins can supply the same

output current of 20mA (typical value). These two power supplies can be used for logic level conversion

circuits between WM620 and external devices, and not recommended as a general-purpose power source for

other application circuits.

VDD_2.6V circuit keeps operating while the WM620 module in sleep mode.

2.1.4 Power on Sequences

Figure 2-4 shows the power on sequencing of WM620.

Figure 2-4

2.2 Power ON/OFF and Reset

2.2.1 ON_OFF

ON_OFF is an input pin with an internal pull-up resistance. Launch a valid low level pulse to ON_OFF can

control the WM620’s system into Start-up or shut-down mode. The pulse width requirement and power on

sequence are shown in figure 2-4.

When the WM620 power on, the VDD_2.6V pin would rise up and keep on 2.6V DC, and then the module's

serial port will automatically issue a keyword string, means that the module system is running and AT

commands is ready.