GL852 USB 2.0 MTT HUB Controller
PCB
Silicon
V
BUS (External 5V)
RESETJ pin (Low active)
R
1
EXT
C
1
R2
Reset
OR
INT
Power good reset circuit
(connected to internal 3.3V)
Figure 5.3 – Power on reset diagram
To fully control the reset process of GL850G, we suggest the reset time applied in the external reset
circuit should longer than that of the internal reset circuit. Timing of POR is illustrated as below figure.
VCC(3.3V)
Power good voltage, 2.5~2.8V
2.7
s
Internal reset
External reset
Figure 5.4 - Power on sequence of GL852
5.2.2 PGANG/SUSPND Setting
To save pin count, GL852 uses the same pin to decide individual/gang mode as well as to output the
suspend flag. The individual/gang mode is decided within 20us after power on reset. Then, about 50ms later,
this pin is changed to output mode. GL852 outputs the suspend flag once it is globally suspended. For
individual mode, a pull low resister greater than 100KΩ should be placed. For gang mode, a pull high
resister which greater than 100KΩ should be placed. In figure 5.6, we also depict the suspend LED
indicator schematics. It should be noticed that the polarity of LED must be followed, otherwise the suspend
current will be over spec limitation (2.5mA).
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