RT5707/A
Functional Block Diagram
OSC
EN
VSEL1
VSEL2
VSEL3
Digital
Control
OTP
Soft-start
OCP
UVLO
VIN
VOUT
R2
R1
FB
V
REF
AMP
PSM/PWM
Control
Gate
Drive
SW
-
+
V
REF
GND
VOUT
Fast
Discharge
EN
Operation
The RT5707/A is a hysteretic constant on time (HCOT)
switching buck converter. The RT5707/A provides Over-
Temperature Protection (OTP) and Over-Current Protection
(OCP) mechanisms to prevent the device from damage
with abnormal operations. When the EN voltage is logic
low, the IC will be shut down with low input supply current
less than 1μA.
Enable
The device can be enabled or disabled by the EN pin.
When the EN pin is higher than the threshold of logic-high
IC goes to normal operation. EN pin High transfer Low
into shutdown mode, the converter stops switching, internal
control circuitry is turned off and trigger discharge function.
That discharge function will close after count 10ms (typ.).
If systems need EN toggle operation that EN turn off time
must larger than 100μs for internal circuit reset time.
UVLO Protection
To protect the chip from operating at insufficient supply
voltage, the UVLO is needed. When the input voltage is
lower than the UVLO falling threshold voltage, the device
will be lockout.
100% Duty Cycle Operation
The converter enters 100% duty cycle operation once the
input voltage decrease and the difference voltage between
input and output is lower than V
TH_100-
. The output voltage
follows the input voltage minus the voltage drop across
the internal P_MOSFET and the inductor. Once the input
voltage increases and trips the 100% mode exit threshold,
V
TH_100+
, the converter backs to normal switching again.
See Figure 1.
Copyright
©
2019 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS5707/A-03 February 2019
www.richtek.com
3
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
