RT9701
Thermal Shut Down Response
T
CH1 1 >
CH3
Thermal Shut Down
T
2 >
CH2
CH1: VCE : 5V/Div
CH3: IOUT@R 1Ωoh:m1A: 5/D0i0vmA/Div
1A/Div
L
CH2: IOUT@short : 500mA/Div
1A/Div
50mS/Div
VIN = 5V
Time (50mS/Div)
Functional Description
Current Limiting and Short Protection
The RT9701 is a high-side single N-channel switch
with active-high enable input.
The current limit circuit is designed to protect the
system supply, the MOSFET switch and the load
from damage caused by excessive currents. The
current limit threshold is set internally to allow a
minimum of 1.1A through the MOSFET but limits the
output current to approximately 1.5A typical. When
the output is short to ground, it will limit to a constant
current 1A until thermal shutdown or short condition
removed.
Input and Output
VIN (input) is the power supply connection to the
circuitry and the drain of the output MOSFET. VOUT
(output) is the source of the output MOSFET. In a
typical circuit, current flows through the switch from
VIN to VOUT toward the load. Both VOUT pins must
be short on the board and connected to the load and
so do both VIN pins but connected to the power
source.
Thermal Shutdown
Thermal shutdown shuts off the output MOSFET if
the die temperature exceeds 130°C and 20°C of
hysteresis forces the switch turning off until the die
temperature drops to 110°C.
Soft Start
In order to eliminate the upstream voltage droop
caused by the large inrush current during hot-plug
events, the “soft-start” feature effectively isolates
power supplies from such highly capacitive loads.
Under-voltage Lockout
UVLO prevents the MOSFET switch from turning on
until input voltage exceeds 1.8V (typical). If input
voltage drops below 1.8V (typical), UVLO shuts off
the MOSFET switch.
DS9701-05 October 2001
www.richtek-ic.com.tw
9
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
