RT7205A
CS-CS+
IFB
OPTO
VFB
VDD
R
OPTO_VDD
A
CS Gain = 40
R
FB1
V
= 0.5V
OFFSET_CS
+
-
+
-
I
o_signal
VDD
UVLO
VDD
UVLO
R
FB2
V
REF_CC
V
REF_CV
10-bit DAC
10-bit DAC
R
OPTO_GND
Figure 1. CV and CC Loops
Interface of D+ and D-
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-bitADC for analog-to-digital conversion, to update the
output current status for the MCU.
The D+ andD- 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
4.2V
3.3V
DPMDO_LEV
10-bit ADC
AIN
External Temperature Sensing
R
H_DPDM
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 RTvoltage is below an over-temperature protection
(OTP) threshold and the condition sustains for a
programmed time delay, the OTP will be triggered.
DPOE
DPO
D+/D-
MCU
DPPE
DPPO
DPI
R
L_DPDM
sDPM_SHORT
3.6V
SHORT SWITCH
RT BIAS
I
BIAS_RT
10-bit ADC
DI
Figure 3. Interface ofD+ andD-
Interface of CC1 and CC2
MCU
RT
DOL
R
NTC
The CC1 and CC2 pins are used for compliance with USB
Type-C specification. When configured as aDownstream
Facing Port (DFP), three current capabilities of 80µA,
180µA, and 330µA, provided by each of the CC pins, will
Figure 2. External Temperature Sensing
Copyright 2018 Richtek Technology Corporation. All rights reserved.
©
is a registered trademark of Richtek Technology Corporation.
www.richtek.com
6
DS7205A-00 February 2018
RICHTEK [ RICHTEK TECHNOLOGY CORPORATION ]
