RT5800
BOOT
Rising
Falling
BOOT
Event Flag
BOOT
Mask
HOT Die
Rising
Falling
HOT Die
Event Flag
HOT Die
Mask
OT
Rising
Falling
OT
Event Flag
OT
Mask
To INT
OV
Mask
OV
Rising
Falling
OV
Event Flag
UV
Rising
Falling
UV
Event Flag
UV
Mask
PG
Rising
Falling
PG
Event Flag
PG
Mask
Figure 7. Overall Detection Function
Watchdog Function
The RT5800 implements a watchdog function which
resets some relative registers, like the output voltage,
to default settings. Register 0x25 can enable or disable
watchdog function of each Buck and provide the
debounce time for selection. The operation of
watchdog reset is shown in Figure 8. Table 1 shows the
registers will be reset when WDOG_RST pin is pulled
low. The I
2
C command needs to be after the
WDOG_RST pull high.
Table 1. Watchdog Reset Register
BUCK1_WDT
0x48
0x49[0]
0x4A
0x4B[0]
0x52
BUCK2_WDT
0x62
0x63[0]
0x64
0x65[0]
0x6C
BUCK3_WDT
0x7C
0x7D[0]
0x7E
0x7F[0]
0x86
The Over-Current Protection
The RT5800 features cycle-by-cycle current-limit
protection on both HSFET and LSFET to prevent the
device from the catastrophic damage in output
short-circuit, over-current or inductor saturation
conditions.
WDOG_RST
Higher
V
SET
Default
Voltage
Lower
V
SET
Reset Related
Register
DEBOUNCE Time
Register Setting
DVS
Slew Rate
VOUT of
BUCKx
Figure 8. Watchdog Reset Operation
The HSFET over-current protection is achieved by an
internal current comparator that monitors the current in
the HSFET during each on-time. The switch current is
compared with the HSFET peak-current limit (I
LIM_H
)
after a certain amount of delay when the HSFET is
turned on each cycle. If an over-current condition
occurs, the converter will immediately turn off the
HSFET and turn on the LSFET to prevent the inductor
current from exceeding the HSFET current limit.
The LSFET over-current protection is achieved by
measuring the inductor current through the LSFET
Copyright © 2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
8
DS5800-00
November 2019
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
