RT7205A
CS- CS+
IFB
OPTO
VFB
VDD
-
+
A
CS Gain = 40
R
OPTO_VDD
V
OFFSET_CS
= 0.5V
I
o_signal
-
+
VDD
UVLO
VDD
UVLO
-
+
V
REF_CC
10-bit DAC
R
OPTO_GND
R
FB1
R
FB2
V
REF_CV
10-bit DAC
Figure 1. CV and CC Loops
Current-Sense Amplifier
To minimize power loss of the current sense resistor in
the converter, the RT7205A includes an amplifier with
virtually zero input offset voltage and with a voltage gain of
40. The sensed output current is amplified by the current-
sense amplifier, shown as
“Io_signal ”
in Figure 1, which
is then sent to the current-loop regulator for constant-
current regulation and also sent to the MCU, by way of an
10-bit ADC for analog-to-digital conversion, to update the
output current status for the MCU.
External Temperature Sensing
The RT7205A provides the RT pin, as a register-
programmable current source to bias a remote thermal
sensor, such as a thermistor (NTC), as shown in Figure
2. If the RT voltage is below an over-temperature protection
(OTP) threshold and the condition sustains for a
programmed time delay, the OTP will be triggered.
3.6V
RT BIAS
10-bit ADC
MCU
DI
DOL
RT
I
BIAS_RT
Interface of D+ and D-
The D+ and D- pins are used for BC1.2 compliance or for
communication with other proprietary protocols. The D+
and D- pins, connected to the MCU via an ADC, can be
reprogrammed for other purposes since they can be used
as an analog/digital input or output.
1.8V 3.3V 4.2V
DPMDO_LEV
10-bit ADC
AIN
R
H_DPDM
DPOE
DPO
MCU
DPPE
DPPO
DPI
R
L_DPDM
D+/D-
sDPM_SHORT
SHORT SWITCH
Figure 3. Interface of D+ and D-
Interface of CC1 and CC2
R
NTC
Figure 2. External Temperature Sensing
Copyright
©
2018 Richtek Technology Corporation. All rights reserved.
The CC1 and CC2 pins are used for compliance with USB
Type-C specification. When configured as a Downstream
Facing Port (DFP), three current capabilities of 80µA,
180µA, and 330µA, provided by each of the CC pins, will
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
6
DS7205A-00
February 2018
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
