RT6257A/B
Abnormal case
detected (UV) t
HICCUP_ON
= 2.5ms
V
OUT
t
HICCUP_OFF
= 5ms
Resume normal
operation
Fault condition
removed
t
0.8ms
External Bootstrap Capacitor
Connect a 0.1μF low ESR ceramic capacitor between
BOOT and LX. This bootstrap capacitor provides the gate
driver supply voltage for the high-side N-channel MOSFET
switch.
Over-Temperature Protection
V
LX
t
The RT6257A/B includes an Over-Temperature Protection
(OTP) circuitry to prevent overheating due to excessive
power dissipation. The OTP will shut down switching
operation when the junction temperature exceeds 150°C.
Once the junction temperature cools down by
approximately 15°C, the IC will resume normal operation.
For continuous operation, provide adequate cooling so
that the junction temperature does not exceed 150°C.
UVP Protection
The RT6257A/B detects under-voltage conditions by
monitoring the feedback voltage on FB pin. When the
feedback voltage is lower than 60% of the target voltage,
the UVP comparator will go high to turn off both internal
high-side and low-side MOSFETs.
Figure 1. UVP and Hiccup Mode
Shut-Down, Start-Up and Enable (EN)
The enable input (EN) has a logic-low level. When V
EN
is
below this level the IC enters shutdown mode. When V
EN
exceeds its logic-high level the IC is fully operational.
V
UVLO
V
IN
V
ENH
V
EN
V
OUT
EN Delay
~0.5ms
Soft Start time
~1.5ms
Figure 2. Power Up Sequence
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS6257A/B-03 October
2018
www.richtek.com
5
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
