IMP805LESA 데이터 시트보기 (PDF) - A1 PROs co., Ltd.

부품명

상세내역

제조사

IMP805LESA

µP Power Supply Supervisor with Battery Backup Switch

A1 PROs co., Ltd. 

IMP690A, 692A, 802L, 802M, 805L

Application Information

Backup Power Sources - SuperCapTM

Capacitor storage, with very high values of capacitance, can be

used as a back-up power source instead of batteries. SuperCapTM

are capacitors with capacities in the fractional farad range. A 0.1

farad SuperCapTM would provide a useful backup power source.

Like the battery supply, it is important that the capacitor voltage

remain below the maximum voltages shown in Table 2. Although

the circuit of Figure 5 shows the most simple way to connect the

SuperCapTM, this circuit cannot insure that an overvoltage condi-

tion will not occur since the capacitor will ultimately charge up to

VCC. To insure that an overvoltage condition does not occur,

the circuit of Figure 6 is preferred. In this circuit configuration, the

diode-resistor pair clamps the capacitor voltage at one diode-

drop below VCC. VCC itself should be regulated within ±5% of

5V for the IMP692A/802M or within ±10% of 5V for the

IMP690A/802L/805L to insure that the storage capacitor does not

achieve an overvoltage state.

Note: SuperCapTM is a trademark of Baknor Industries

+5V

Operation Without a Backup Power Source

When operating without a back-up power source, the VBATT pin

should be connected to GND and VOUT should be connected to

VCC, since power source switchover will not occur. Connecting

VOUT to VCC eliminates the voltage drop due to the ON-resistance

of the PMOS switch.

Power-Fail Comparator

The Power Fail feature is an independent voltage monitoring

function that can be used for any number of monitoring activities.

The PFI function can provide an early sensing of power supply

failure by sensing the voltage of the unregulated DC ahead of

the regulated supply sensing seen by the backup-battery

switchover circuitry.

The PFI pin is compared to a 1.25V internal reference. If the volt-

age at the PFI pin is less than this reference voltage, thePFO pin

goes low. By sensing the voltage of the raw DC power supply, the

microprocessor system can prepare for imminent power-loss,

especially if the battery backup supply is not enabled. The input

voltage at the PFI pin results from a simple resistor voltage

divider as shown in Figure 7.

VCC

VOUT

To Static RAM

+5V

VBATT RESET

(RESET)

+

0.1F

GND

To µP

( ) IMP805L

690A_07.eps

Figure 5. Capacitor as a backup power source

+5V

VCC

VOUT

To Static RAM

VCC

R1

IMP690A

IMP692A

PFI IMP802L PFO

IMP802M

IMP805L

R2

GND

+5V

PFO

A

B

0V

+

100k

0.1F

VBATT RESET

IMP692A

IMP802M

GND

To µP

( ) IMP805L

690A_08.eps

Figure 6. Capacitor as back-up Power Source - Voltage

clamped to 0.5V below VCC

A

5R 2 < 1.25V

R1 + R 2

B

5R 2 > 1.25V

R1 + R 2

690A_09.eps

Figure 7. Simple Voltage divider sets PFI trip point

7

Share Link: