RT6266
Soft-Start (SS)
Internal Current Limit Protection
An internal current source charges an internal capacitor
to build a soft-start ramp voltage. The FB voltage will
track the internal ramp voltage during soft-start interval.
The typical soft-start time is 3.5ms.
When the external RSENSE is too small and the external
peak current is higher than 4.4A, the high-side switch
will turn off immediately and then turn at the next clock
cycle. The inductor’s peak current will be limited at 4.4A
by internal current limit.
Output Line Drop Compensation
If the trace from RT6266 output terminator to the load is
too long, there will be a voltage drop on the long trace
which is variable with load current. RT6266 is capable
of compensating the output voltage drop to keep a
constant voltage at load, whatever the load current is.
The output voltage is compensated by feeding a
current to the top feedback resistance R1. The load line
compensation gain can be programmed according to
RSENSE and Rtrace values.
Output Short-Circuit Protection
When VOUT is short (VFB < 0.3V), the short-circuit
protection function can be started that restart the
regulator cycle by cycle. The cycle time is set by the
driver internally. The internal current limit time is t1 and
the regulator off time is t2. The typically t1 = 5ms, t2 =
200ms.
I
(A)
OUT
R
SENSE
Rtrace1
Rtrace2
Vload
+
I
OUT
CSP
CSN
_
R1
R2
FB
Time
t2
t1
Under Voltage Lockout (UVLO)
IOUT RSENSE 20μR1 IOUT Rtrace
To avoid mis-operation at low input voltage, when input
voltage falls below 6.2V, and under voltage lockout is
induced and the device is disabled.
Rtrace
R1
20μRSENSE
Thermal Shutdown
Output Over Voltage Protection (OVP)
The over temperature protection function will shut down
the switching operation when the junction temperature
exceeds 150C. Once the junction temperature cools
down by approximately 30C, the converter will
automatically resume switching.
The VOUT Over Voltage is sensed by CSN pin. When
CSN > 5.8V, the high side switch will be turned off
immediately. When CSN < 5.5V, the driver will recovers
to normal state automatically.
External Current Limit Protection
The external current limit is set by outside resistance
(RSENSE). The average current is limited according to
the following equation :
100mV
Average Current_Limit (A)
RSENSE
Copyright © 2015 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
4
DS6266-00 March 2015
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
