BU21170MUV Datasheet, PDF (19/33 Pages) Rohm – Capacitive Switch Controller IC

BU21170MUV
Power on sequence
Power supply pin is VDD only. AVDD and DVDD are supplied by each LDO included this IC, so that have no priority
about power on sequence. When VDD reaches to the effective voltage, power-on-reset which initializes the digital block
is released.
Power-on-reset is monitoring VDD, so it needs that decoupling capacitor’s value is suitable for VDD rising time. (DVDD’s
rising time < VDD’s rising time.)
Recommended value of external capacitors
C1 0.1uF VDD decoupling capacitor
VDD
C2 1.0uF DVDD decoupling capacitor
C3 2.2uF AVDD decoupling capacitor
VDD
AVDD
C₁
DVDD
VDD
BU21170MUV
C₂
C₃
Over 100usec
VSS
DVDD
3.30V
1.50V
GND
AVDD
Figure 12. Arrangement of external decoupling capacitors
2.73V
Figure 13. Timing chart of power on sequence
When power-on-reset is released, MPU starts initial sequence. Inform by the INT port to the host that the initialization
has been completed. After verify that the initialization has been completed, the host will need to resend the command
to this IC.
In the case that WDTR is released as well, MPU starts initial sequence. If WDTR has released, all registers of this IC
have been initialized. So the host will need to resend the command to this IC.
VDD
Power on Reset
(ActiveLow)
port LED
port INT
Initialize IC
about 300usec
Hi-Z about 100usec
Interrupt of Initialization Done
Figure 14. Timing chart of initialization
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TSZ22111・15・001
19/29
TSZ02201-0L5L0F300830-1-2
14.Jul.2016 Rev.002