RT7800B
AnyVoltTM Output Voltage Adjustment
Over-Voltage Protection (OVP)
In Figure 2, OVPs are detected at VBUS and VX pins
with programmable (8-bit) trip-level from 5.5V up to 24V.
Each OVPdebounce time is programmable to meet various
application requirements.
In a Provider application, the RT7800B provides the
“AnyVoltTM” feature for multiple selections of output
voltage so as to achieve high power efficiency of switching/
linear charger in portable devices such as smart phone,
tablet PC, and etc. The RT7800B are designed to gradually
increase/decrease the Provider output voltage from 3V to
20V or 20V to 3V with typical 50mV/step.Aprogrammable
sinking current (9-bit, 0 to 350μA), flowing into DAC_CV
pin via a high-side feedback resistor of aDC-DC converter,
is programmed to adjust output voltage of the DC-DC
converter, where DAC_CV pin is connected to voltage
feedback (FB) pin of theDC-DC converter.
Under-Voltage Protection (UVP)
In Figure 2, UVP is detected at VBUS pin with
programmable (8-bit) trip-level from 3V to 20V. UVP
debounce time is programmable to avoid false triggering
and to meet various application requirements.
AnyCurrentTM Over-Current Protection (OCP)
Because a robust system is very important in USB PD
operations, theAnyCurrentTM OCP feature allows setting
a most suitable OCP trip level for a negotiated PD system.
The RT7800B integrates a current-sense amplifier to detect
the output current for OCP and to indicate the value of
output current. The amplifier, designed with offset
cancellation function, can accurately detect the current-
sense voltage (i.e., output current x current-sense resistor)
between CSP and CSNpins. The OCP trip voltage setting
is programmable (8-bit) and recommended from 10mV to
60mV.
Cable Voltage Drop Compensation (CDC)
In a power delivery operation, both Provider and Consumer
configurations of the RT7800B can monitor the voltages
on each VBUS pin to compensate voltage drop across
USB cable. The Consumer RT7800B can request higher
VBUS voltage from the Provider through PD protocol
communication to achieve accurate application voltage.
Resistor
VBUS
Divider
+
Programmable
VBUS OVP
Programmable
-
Debounce Time
OVP Threshold
Comparator 1
-
Programmable
VBUS UVP
Programmable
UVP Threshold
+
Debounce Time
Comparator 2
Resistor
Divider
VX
+
Programmable
VX OVP
Programmable
OVP Threshold
Debounce Time
-
Comparator 3
Figure 2
Copyright 2017 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
DS7800B-00 May 2017
www.richtek.com
7
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
