L9963E datasheet(149/184 Pages) STMICROELECTRONICS

149 / 184 page

6.9.2

Differential measurement

In the single ended approach the external NTC is connected between two PCB global inputs. This eliminates the

issue of GND shift but requires an additional global pin for each NTC. Using two GPIOs to measure the NTC

voltage is not mandatory, but simplifies the calculations.

Figure 45. Example of NTC differential measurement

L9963E

VTREF

GPIO4

RPU

CFIL

RFIL

RNTC

GPIO5

RFIL

RPD

AGND

CESD

Table 84. NTC analog front end BOM for differential measurement

Components Value

Unit

Max.

tolerance

Rating

Comments

RNTC

kΩ

Recommended external NTC typical value @25 °C. The

NTCALUG02A103F is a good option for evaluation purposes

RFIL

3.3

kΩ

10%

1.5 W

Protect the GPIO in case of external STG/STB. Limit the

ESD inrush current. Filter the NTC signal: cut-off frequency

fC= 1

4πRFILCFIL.

Do not use thin film resistors on these lines connected to ECU

global pins. They could drift upon System Level ESD strikes.

Use thick film or metal foil instead.

CFIL

100

10%

16 V

Protect against ESD events and ISO spikes. Filter the NTC

signal: cut-off frequency is

fC= 1

2πRFILCFIL.Connectto

AGND.

L9963E

NTC analog front end

DS13636 - Rev 12

page 149/184

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