RT5701
the extra power consumption by body diode or negative
inductor current. Regard with this defect, AZC adjusts
current threshold continuously when the RT5701 is
operating. With AZC circuit, the RT5701 could avoid
negative current in PSM mode and could achieve higher
efficiency performance.
Minimum Peak Current
Minimum peak current is an evolution version from
minimum on time. Rather than fixed minimum on time,
Minimum peak current produce the
“effective
minimum
on time” which could be adjusted according to
V
IN
/V
OUT
condition.
T
ON
=
L
×
I
MIN_Peak
V
IN
−
V
OUT
reference voltage into another reference voltage in steps
smoothly. The slew rate of the internal reference voltage
is around 3mV / 10μs. Please note DVS function could
only be available in the same output voltage bank.
Remote Ground Sensing
The RT5701 can deliver output current up to 4A. Inevitably,
there is voltage drops due to the routing trace resistance
between output node and chip location, especially when
heavy loading. Also, voltage drops exist
in ground trace.
Remote ground sensing pin, GNDR, can tell the converter
the lost drops to compensate to the correct and accuracy
voltage level.
Active Output Discharge
To make sure that no residual voltage remains in the power
supply rail, an active discharge path can ground the output
voltage. The output gets discharged by the LX pin with a
typical discharge resistor when the device shuts down.
This feature can be easily disabled or enabled with register
0x12.Discharge. By default the discharge path is active.
The default value of the feature is factory programmable.
Power Good
When the output voltage is higher than Power Good rising
threshold, the Power Good flag, register 0x01.SEN_PG
is high.
Under-Voltage Lockout (UVLO)
The UVLO continuously monitors the PVIN voltage to make
sure the device works properly. When the PVIN is high
enough to reach the UVLO high raising threshold voltage,
2.4V, the converter softly starts. When the PVIN decreases
to its UVLO low threshold voltage, 2.3V, the device will
shut down. The event is recorded in register
0x18.PVIN_UVLO. The record can be reset with I
2
C
interface or automatically reset by re-power-on AVDD.
Output Under-Voltage Protection (UVP)
When the output voltage is lower than UVP threshold
(~50% of nominal target) after soft-start, the UVP is
triggered. The converter will be latched and the output
voltage will no longer be regulated during
UVP latched
state. Re-power-on input voltage or EN pin can unlatch
It's an advantage to not provide too much energy at low
duty; also, to not provide too less energy at high duty.
When the
converter is in PSM operation, every time pulse
skip duration finishes, the converter will provide current
energy for output loading by turning on P-MOSFET until
inductor current achieve minimum peak current.
Low Power Mode (LPM)
The RT5701 provides Low Power Mode (LPM) to save
more quiescent consumption. With maximum output
current ability, 1mA, LPM enhances the efficiency at load
below 100μA, more than the Pulse Skipping Mode (PSM)
does. This extremely efficiency improvement may extend
battery life, especially in stand-by mode of hand held
products.
Enabling
The converter can be enabled or disabled by IC pin, EN.
For more flexibility, users can turn on/off the converter by
I
2
C programming. There are ENSEL register bit located in
register 0x10.ENSEL1 and 0x11.ENSEL0 to control
internal enable signal for both VSEL selection high/low.
Dynamic Voltage Scaling (DVS)
Users can select required output voltage bank and preferred
output voltage by I
2
C programming. When output voltage
is changed, the RT5701 provides Dynamic Voltage Scaling
(DVS) skill to prevent any undershoot or overshoot when
output voltage transition. The DVS means to adjust one
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
is a registered trademark of Richtek Technology Corporation.
DS5701-02 March 2018
www.richtek.com
5
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
