RT8175A Datasheet, PDF (42/47 Pages) Richtek Technology Corporation – Single-Phase Controller with Integrated Driver

RT8175A
VCC
PVCC
POR
EN
1ms
SVID ^Invalid
Valid
Invalid
Figure 20. Timing Chart for POR Process
Precise Reference Current Generation, IBIAS
Analog circuits need very precise reference voltage/current
to drive/set these analog devices. The RT8175A provides
a 2V voltage source at the IBIAS pin, and a 100kΩ resistor
is required to be connected between IBIAS pin and analog
ground to generate a very precise reference current.
Through this connection, the RT8175A will generate a
20μA current from the IBIAS pin to analog ground, and
this 20μA current will be mirrored inside the RT8175A for
internal use. The IBIAS pin can only be connected with a
100kΩ resistor to GND for internal analog circuit use. The
resistance accuracy of this resistor is recommended to
be 1% or higher. Figure 21 shows the IBIAS setting circuit.
Current Mirror
2V
+
-
20µA
IBIAS
100k
Figure 21. IBIAS Setting Circuit
TSEN and VR_HOT
The VR_HOT signal is an open-drain signal which is used
for VR thermal protection. When the sensed voltage in
TSEN pin is over 1.887V under V_CC is exact 5V condition,
the VR_HOT signal will be pulled-low to notify CPU that
the thermal protection needs to work. Please note that,
the VR thermal protection is only valid under PS0, PS1
and PS2 condition. According to Intel VR definition,
VR_HOT signal needs acting if VR power chain
temperature exceeds 100°C. Placing an NTC thermistor
at the hottest area in the VR power chain and its
connection is shown in Figure 22, to design the voltage
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divider elements (R1, R2 and NTC) so that V_TSEN = 1.887V
at 100°C. The resistance accuracy of TSEN network is
recommended to be 1% or higher.
V_TSEN
= V_CC  _{R2 +}
R2
_{R1//RNTC(100C)} 
= 1.887V
VDDIO
VR_HOT
VCC
R1
NTC
TSEN
+
-
R2
1.887V
SetGND
Figure 22. VR_HOT Circuit
VBOOT
The RT8175A provides controllable VBOOT function as
shown in Figure 23. The VBOOT voltage can be set by
the VBOOTSEL pin. Table 11 shows the VBOOT voltage
setting in VBOOTSEL pin. For example, when VBOOT =
1V, the VBOOTSEL set voltage will be between 1.3V and
3.7V. It's noted that, if floating VBOOTSEL pin that the
VBOOT voltage will not be defined.
V_CC
R1
VBOOTSEL
R2
SetGND
Figure 23. VBOOTSEL Circuit.
Table 11. VBOOTSEL Pin setting for VBOOT
VBOOTSEL

R2
R1 R2

5V
VBOOT
Min Typical Max Unit
0
0.6
1.2
V
0.9
1.3
2.5
3.7
V
1.0
3.8
4.4
5
V
1.1
Differential Remote Sense Setting
The VR provides differential remote-sense inputs to
eliminate the effects of voltage drops along the PC board
traces as signified as Figure 24. CPU internal power routes
is a registered trademark of Richtek Technology Corporation.
DS8175A-02 September 2015