RT8206A/B
Table 2. Operation Mode Truth Table
Mode
Condition
Comment
Transitions to discharge mode after a VIN POR and
after REF becomes valid. LDO and REF remain active.
Power-UP
PVCC < UVLO threshold
RUN
ENLDO = high, EN1 or EN2 enabled Normal Operation.
Over voltage
Protection
Either output > 111% of nominal
level.
LGATEx is forced high. LDO and REF active. Exited by
VIN POR or by toggling ENLDO.
Both UGATEx and LGATEx are forced low until enter
discharge mode terminates. LDO and REF are active.
Exited by VIN POR or by toggling ENLDO, EN1, or
EN2.
Either output<70% of nominal level
after 3ms time-out expires and output
is enabled.
Under voltage
Protection
Either SMPS output is still high in
either standby mode or shutdown
mode.
During discharge mode, the output capacitor
discharges to GND through an internal 20Ω switch.
Discharge
ENx < startup threshold,
ENLDO = high.
Standby
LGATEx stays low. LDO and REF active.
Shutdown
EN1, EN2, ENLDO=low
All circuitry off.
Thermal Shutdown T > +150°C
All circuitry off. Exit by VIN POR or by toggling ENLDO.
J
Table 3. Power-Up Sequencing
ENLDO (V)
V
EN1
(V) VEN2 (V)
LDO
5V SMPS1
3V SMPS2
Low
X
X
Off
Off
Off
On
“>2V” High
“>2V” High
“>2V” High
“>2V” High
“>2V” High
“>2V” High
“>2V” High
“>2V” High
“>2V” High
Low
Low
Low
REF
REF
REF
High
High
High
Low
REF
High
Low
REF
High
Low
REF
High
Off
Off
Off
Off
Off
Off
Off
On
Off
Off
On
Off
(after REF powers up)
On
(after REF powers up)
On
(after REF powers up)
On
(after REF powers up)
On
(after REF powers up)
On
On
(after REF powers up)
On
(after SMPS2 on)
On
On
On
(after REF powers up)
On
On
(after REF powers up)
(after SMPS1 on)
On
On
(after REF powers up)
DS8206A/B-03 December 2009
www.richtek.com
25
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
