RT3612EB datasheet(36/47 Pages) RICHTEK

36 / 47 page

RT3612EB

DS3612EB-02 December 2019

www.richtek.com

is a registered trademark of Richtek Technology Corporation.

Figure 22. Multi-Function Pin Setting Mechanism for

TSEN

Thermal Monitoring and Indicator

TSEN pin processes two functions of PIN-SETTING

(function setting) and thermal monitoring as shown in

Figure 22. The timing chart and related signals are shown

in Figure 23. After power on, TSEN has three operation

modes : PIN-SETTING, Pre-Thermal Sense and Thermal

Sense Mode. The corresponding function blocks of the

three modes are shown in Figure 22. In PIN-SETTING

Mode, TSEN pin voltage = 3.2V x R2/(R1 + R2) with

VREF06 = 3.2V and is coded by ADC and stored in PIN-

SETTING register. In Pre-Thermal Sense Mode, TSEN pin

voltage = 0.6V x R2/(R1 + R2) with VREF06 = 0.6V and

is coded and stored in Pre-Thermal Register. This part

helps Thermal Sense Mode calculation. In Thermal Sense

Mode, TSEN pin voltage = 0.6V x R2/(R1 + R2) + 80

μA x

[(R1//R2) + R3] with VREF06 = 0.6V and is coded. Pre-

Thermal Register code is subtracted from the result and

the value is stored in Thermal Register (The corresponding

TSEN voltage = 80

μA x [(R1//R2) + R3] that's defined as

Thermal Voltage. R3 is the NTC thermistor network to

sense temperature.) NTC thermistor is recommended to

to be placed near the MOSFET, the hottest area in the

PCB. Higher temperature causes smaller R3 and lower

TSEN. According to NTC thermistor temperature curve,

design Thermal Voltage v.s Temperature with proper Rx

network to meet Table 16. 100

°C Thermal Voltage = 80μA

x [(R1//R2) + R3, 100

°C] = 1.092V must be met. Controller

processes TSEN pin voltage to report temperature zone

VR_HOT# is pulled low to indicate thermal alert. The

VR_HOT# signal is an open-drain signal. Thermal Register

data is updated every 100

μs and averaged every 800μs.

The resistance accuracy of TSEN network is recommended

to be less than 1% error.

VREF06

= 0.6V

TSEN

80µA

RNTC

VDDIO

PIN-SETTING

ADC

Pre-Thermal

Thermal Register

Thermal Sense Mode

1.092V

Thermal Sense Mode

VR_HOT#

VREF06

= 0.6V

TSEN

80µA

RNTC

VDDIO

PIN-SETTING

ADC

Pre-Thermal

Thermal Register

Thermal Sense Mode

1.092V

Pre-Thermal

Sense Mode

VR_HOT#

VREF06

= 3.2V

TSEN

80µA

RNTC

PIN-SETTING

ADC

Pre-Thermal

1.092V

VR_HOT#

VDDIO

Thermal Register

Thermal Sense Mode

PIN-SETTING Mode

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