Datasheet

R_Setpoint

3V3_VCC

AGND

NTC

AGND

T_SENSE

Optional

Temperature

Sensor

R _ Setpoint 2.3 R _ NTC= ´

bq500211A

SLUSBB1A – DECEMBER 2012–REVISED SEPTEMBER 2013

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Shut Down via External Thermal Sensor or Trigger

Typical applications of the bq500211A will not require additional thermal protection. This shutdown feature is

provided for enhanced applications and is not only limited to thermal shutdown. The key parameter is the 1.0 V

threshold on pin 2. Voltage below 1.0 V on pin 2 causes the device to shutdown.

The application of thermal monitoring via a Negative Temperature Coefficient (NTC) sensor, for example, is

straightforward. The NTC forms the lower leg of a temperature dependant voltage divider. The NTC leads are

connected to the bq500211A device, pin 2 and GND. The threshold on pin 2 is set to 1.0 V, below which the

system shuts down and a fault is indicated (depending on LED mode chosen).

To implement this feature follow these steps:

1) Consult the NTC datasheet and find the resistence vs temperature curve.

2) Determine the actual temperature where the NTC will be placed by using a thermal probe.

3) Read the NTC resistance at that temperature in the NTC datasheet, that is R_NTC.

4) Use the following formula to determine the upper leg resistor (R_Setpoint):

(1)

The system will restore normal operation after approximately five minutes or if the receiver is removed. If the

feature is not used, this pin must be pulled high.

NOTE

Pin 2 must always be terminated, else erratic behavior may result.

Figure 6. Negative Temperature Coefficient (NTC) Application

Product Folder Links: bq500211A