LTC2914IDHC-2 データシートの表示（PDF） - Linear Technology

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LTC2914IDHC-2

Quad UV/OV Positive/Negative Voltage Monitor

Linear Technology 

LTC2914

APPLICATIONS INFORMATION

Voltage Monitoring

The LTC2914 is a low power quad voltage monitoring cir-

cuit with four undervoltage and four overvoltage inputs. A

timeout period that holds OV or UV asserted after all faults

have cleared is adjustable using an external capacitor and

is externally disabled.

Each voltage monitor has two inputs (VHn and VLn) for

detecting undervoltage and overvoltage conditions. When

configured to monitor a positive voltage Vn using the

3-resistor circuit configuration shown in Figure 1, VHn is

connected to the high-side tap of the resistive divider and

VLn is connected to the low-side tap of the resistive divider.

If an input is configured as a negative voltage monitor, the

outputs UVn and OVn in Figure 1 are swapped internally. Vn

is then connected as shown in Figure 2. Note, VHn is still

connected to the high-side tap and VLn is still connected

to the low-side tap.

Polarity Selection

The three-state polarity-select pin (SEL) selects one of three

possible polarity combinations for the input thresholds,

as described in Table 1. When an input is configured for

negative supply monitoring, VHn is configured to trigger an

overvoltage condition and VLn is configured to trigger an

undervoltage condition. With this configuration, an OV con-

dition occurs when the supply voltage is more negative than

the configured threshold and a UV condition occurs when

the voltage is less negative than the configured threshold.

Vn

RC

LTC2914

VHn

–

UVn

+

RB

+– 0.5V

–

VLn

+

OVn

RA

2914 F01

Figure 1. 3-Resistor Positive UV/OV Monitoring Configuration

The three-state input pin SEL is connected to GND, VCC or

left unconnected during normal operation. When the pin

is left unconnected, the maximum leakage allowed from

the pin is ±10μA to ensure it remains in the open state.

Table 1 shows the three possible selections of polarity

based on the SEL pin connection.

Table 1. Voltage Polarity Programming (VUOT = 0.5V Typical)

SEL

V3 INPUT

V4 INPUT

VCC

Open

Positive

VH3 < VUOT → UV

VL3 > VUOT → OV

Positive

Positive

VH4 < VUOT → UV

VL4 > VUOT → OV

Negative

VH3 < VUOT → UV

VL3 > VUOT → OV

GND

Negative

VH4 < VUOT → OV

VL4 > VUOT → UV

Negative

VH3 < VUOT → OV

VL3 > VUOT → UV

VH4 < VUOT → OV

VL4 > VUOT → UV

3-Step Design Procedure

The following 3-step design procedure allows selecting

appropriate resistances to obtain the desired UV and OV trip

points for the positive voltage monitor circuit in Figure 1

and the negative voltage monitor circuit in Figure 2.

LTC2914

REF

1V

RA

VHn

–

OVn

+

RB

+– 0.5V

–

VLn

+

UVn

RC

2914 F02

Vn

Figure 2. 3-Resistor Negative UV/OV Monitoring Configuration

2914fa

8

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