RT6296A
Frequency vs. Ouput Current
1000
TTH
2.5V
Internal Regulator
The internal regulator generates 5V power and drive
internal circuit. When VIN is below 5V, PVCC will drop
Frequency (kHz)1
100
TTH = 0.5V
TTH = 1.2V
with VIN. A capacitor (>0.1F) between PVCC and
GND is required.
Internal Soft-Start Function
10
The RT7296A provides internal soft-start function. The
V
IN
= 12V, V
OUT
= 5V,
L = 5.6μH, C
OUT
= 22μF x 2
1
0.01
0.1
1
10
soft-start function is used to prevent large inrush
current while converter is being powered-up. Output
Ouput Current (A)
voltage starts to rise 1.2ms after EN rising, and the
soft-start time (V
FB
from 0V to 0.8V) is 1.5ms.
VIN = 12V
VIN
VCC = 5V
Figure 4. Frequency vs Output Current, V
OUT
= 5V
Under-Voltage Lockout Threshold
The IC includes an input Under Voltage Lockout
Protection (UVLO). If the input voltage exceeds the
UVLO rising threshold voltage (3.9V), the converter
resets and prepares the PWM for operation. If the input
voltage falls below the UVLO falling threshold voltage
VCC
EN
1.2ms
1.5ms
VOUT
(3.25V) during normal operation, the device stops
switching. The UVLO rising and falling threshold
voltage includes a hysteresis to prevent noise caused
reset.
Chip Enable
The EN pin is the chip enable input. Pulling the EN pin
low (<1.1V) will shutdown the output voltage. During
shutdown mode (<0.4V), the RT6296A’s quiescent
current drops to lower than 1A. Driving the EN pin
high (>1.6V) will turn on the device.
Operating Frequency and Synchronization
The internal oscillator runs at 500kHz (typ.) when the
EN/SYNC pin is at logic-high level (>1.6V). If the EN
pin is pulled to low-level over 8s, the IC will shut down.
The RT6296A can be synchronized with an external
clock ranging from 200kHz to 2MHz applied to the
EN/SYNC pin. The external clock duty cycle must be
from 20% to 80% with logic-high level = 2V and
logic-low level = 0.8V.
Copyright © 2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
High-Side MOSFET Over-Current Limit
The RT6296A features cycle-by-cycle current limit
protection
and
prevents
the
device
from
the
catastrophic damage in output short circuit, over
current or inductor saturation. During the on-time of the
high side switch, the device monitors the switch current.
If the switch current overs the current limit threshold,
the device turns off the high side switch to prevent the
device from damage.
Output Under-Voltage Protection
The RT6296A includes output under-voltage protection
(UVP) against over-load or short-circuited condition by
constantly monitoring the feedback voltage V
FB
. If V
FB
drops below the under-voltage protection trip threshold,
50% (typ.) of the internal reference voltage, the UV
comparator will go high to turn off the internal high-side
MOSFET
switches.
If
the
output
under-voltage
DS6296A-04
January 2018
www.richtek.com
5
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
