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Operation

Table 3 shows the SVS SENSE threshold accuracy based on the resistor tolerance and the reference

accuracy values.

Table 3. SVS SENSE Threshold Accuracy and Resistor Divider Selection

R1(R5) R2 (R6)

Monitor

Threshold Voltage Selection Calculation Threshold Accuracy

SVS

(nominal) (0.1% Tol) (0.1% Tol) Min/Max Threshold Voltage

Voltage

Ω Ω

1.8 V 1.699 V (5.61% below SVS Voltage) 1M 422K 1.68V / 1.72V

3.3 V 3.118 V (5.52% below SVS Voltage) 1M 191K 3.08V / 3.15V

5.0 V 4.667 V (6.66% below SVS Voltage) 1M 120K 4.61V / 4.72V

3.4 SETUP: Connecting to the SVS Circuit of U1 (U2).

3.4.1 Connect the VCC power supply to power the circuit from J1 (J8) to ground, GND1 (GND2) at J4 (J11).

3.4.2 Observe the output between Sense_out, J6 (J12), and ground, J7 (J13), using a voltmeter and or an

oscilloscope.

3.4.3 Enable the SVS circuit by correctly jumpering J3 (J10) in accord with the Table 2 description.

3.4.4 Connect the monitored voltage the SVS SENSE connector, J2 (J9), and ground, J4 (J11).

3.4.4.1 Vary the monitored voltage level, at SVS SENSE, as needed to see the various responses to the

output at Sense_out.

4 Operation

4.1 Operation Description

After applying power to VCC, followed by the active Enable, the Sense_out will become active after the

Enable delay, provided that the SVS SENSE voltage is above the programmed threshold voltage. When

the SVS SENSE voltage falls below the threshold voltage minus the hysteresis voltage (V

HYS

) - where

HYS

= 5 mV x (1 + R1/R2) - the Sense_out becomes immediately inactive (within 16 µs typical). Assuming

that VCC is within operational range and that the EN is active, the output will toggle when the input SVS

SENSE voltage rises and falls above-below the threshold.

4.2 Test Results

Figure 2 shows the Sense_out voltage (red, C2) becoming active high approximately 192 ms (Input Delay)

after the SVS SENSE voltage (gold, C1) rises above the threshold voltage. The Sense_out signal

immediately falls when the SVS SENSE voltage falls below the threshold. The VCC voltage has been

previously set to 3.3 V. The SVS circuit being demonstrated employs the TPS3895A supervisory IC.

SLVU524A–August 2011–Revised September 2011 TPS389xA-xP-EVM047 Evaluation Modules

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