TPS3700

www.ti.com

SBVS187B – FEBRUARY 2012 – REVISED APRIL 2012

GENERAL DESCRIPTION

The TPS3700 combines two comparators for over- and undervoltage detection. The TPS3700 is a wide-supply

voltage range (1.8 V to 18 V) device with a high-accuracy rising input threshold of 400 mV (1% over temperature)

and built-in hysteresis. The outputs are also rated to 18 V and can sink up to 40 mA.

The TPS3700 is designed to assert the output signals, as shown in Table 1. Each input pin can be set to monitor

any voltage above 0.4 V using an external resistor divider network. With the use of two input pins of different

polarities, the TPS3700 forms a window comparator. Broad voltage thresholds can be supported that allow the

device to be used in a wide array of applications.

Table 1. TPS3700 Truth Table

CONDITION

OUTPUT

STATUS

OUTA high

Output A not asserted

OUTA low

Output A asserted

OUTB low

Output B asserted

OUTB high

Output B not asserted

INPUTS (INA+, INB–)

The TPS3700 combines two comparators. Each comparator has one external input (inverting and noninverting);

the other input is connected to the internal reference. The comparator rising threshold is designed and trimmed

to be equal to the reference voltage (400 mV). Both comparators also have a built-in falling hysteresis that

makes the device immune to supply rail noise and ensures stable operation.

The comparator inputs can swing from ground to 6.5 V, regardless of the device supply voltage used. Although

not required in most cases, it is good analog design practice to place a 1-nF to 10-nF bypass capacitor at the

comparator input for extremely noisy applications in order to reduce sensitivity to transients and layout parasitics.

For comparator A, the corresponding output (OUTA) is driven to logic low when the input INA+ voltage drops

Figure 2.

For comparator B, the corresponding output (OUTB) is driven to logic low when the voltage at input INB–

Figure 2. Together, these comparators form a window-detection function as discussed in the Window

Comparator section.

OUTPUTS (OUTA, OUTB)

In a typical TPS3700 application, the outputs are connected to a reset or enable input of the processor [such as

a digital signal processor (DSP), central processing unit (CPU), field-programmable gate array (FPGA), or

application-specific integrated circuit (ASIC)] or the outputs are connected to the enable input of a voltage

regulator [such as a dc-dc or low-dropout regulator (LDO)].

The TPS3700 provides two open-drain outputs (OUTA and OUTB); pull-up resistors must be used to hold these

lines high when the output goes to high impedance (not asserted). By connecting pull-up resistors to the proper

voltage rails, the outputs can be connected to other devices at correct interface voltage levels. The TPS3700

outputs can be pulled up to 18 V, independent of the device supply voltage. To ensure proper voltage levels,

some thought should be given while choosing the pull-up resistor values. The pull-up resistor value is determined

Characteristics table. By using wired-AND logic, OUTA and OUTB can be merged into one logic signal.

Table 1 and the Inputs section describe how the outputs are asserted or de-asserted. Refer to Figure 2 for a

timing diagram that describes the relationship between threshold voltages and the respective output.

Copyright © 2012, Texas Instruments Incorporated

Submit Documentation Feedback

9

Product Folder Link(s): TPS3700