MAX6848 데이터 시트보기 (PDF) - Maxim Integrated

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MAX6848

Low-Power, Adjustable Battery Monitors with Hysteresis and Integrated µP Reset

Maxim Integrated 

Low-Power, Adjustable Battery Monitors with

Hysteresis and Integrated µP Reset

Pin Description

PIN

MAX6846/MAX6847 MAX6848/MAX6849

1

1

2

2

3

3

4

—

5

5

6

—

NAME

VDD

GND

LTHIN

LBO

RESET

MR

FUNCTION

VDD Supply. Device power supply if VDD is greater than VCC.

Ground

LTH Threshold Monitor Input. A resistor-divider network sets the low

threshold associated with LBOL and LBO.

Low-Battery Output, Active-Low, Open-Drain. LBO is asserted when LTHIN

drops below the VLTH specification and remains asserted until HTHIN rises

above the VHTH specification for at least 150ms.

Reset Output, Active-Low, Push-Pull, or Open-Drain. RESET goes from high

to low when the VCC input drops below the selected reset threshold and

remains low for the VCC reset timeout period after VCC exceeds the reset

threshold. RESET is one-shot edge-trigger pulsed low for the MR reset

timeout period when the MR input is pulled low. RESET is an open-drain

output for the MAX6846/MAX6848, and a push-pull output for the

MAX6847/MAX6849. The push-pull outputs are referenced to VCC. RESET

is guaranteed to be in the correct logic state for VDD or VCC ≥ 10V.

Manual Reset Input, Active-Low, Internal 1.5kΩ Pullup to VCC. Pull MR low

to assert a one-shot reset output pulse for the MR reset timeout period.

Leave unconnected or connect to VCC if unused. The MR input is

debounced for MR rising edges to prevent false reset events.

7

7

HTHIN

HTH Threshold Monitor Input. A resistor-divider network sets the high

threshold associated with LBOH and LBO.

8

8

VCC

VCC Voltage Input. Input for VCC reset threshold monitor and device power

supply if VCC is greater than VDD.

Low-Battery Output High, Active-Low, Open-Drain. LBOH is asserted when

—

6

LBOH HTHIN drops below the VHTH- specification. LBOH is deasserted when

HTHIN rises above the VHTH+ specification for at least 150ms.

Low-Battery Output Low, Active-Low, Open-Drain. LBOL is asserted when

—

4

LBOL LTHIN drops below the VLTH- specification. LBOL is deasserted when

LTHIN rises above the VLTH+ specification for at least 150ms.

Detailed Description

The MAX6846–MAX6849 family is available with several

monitoring options. The MAX6846/MAX6847 have single

low-battery outputs and the MAX6848/MAX6849 have

dual low-battery outputs (see Figures 1a and 1b).

The MAX6846–MAX6849 combine a 615mV reference

with two comparators, logic, and timing circuitry to pro-

vide the user with information about the charge state of

the power-supply batteries. The MAX6848/MAX6849

monitor separate high-voltage and low-voltage thresh-

olds to determine battery status. The output(s) can be

used to signal when the battery is charged, when the

battery is low, and when the battery is empty. User-

adjustable thresholds are ideal for monitoring single-

cell Li+ or multicell alkaline/NiCd/NiMH power supplies.

When the power-supply voltage drops below the speci-

fied low threshold, the low-battery output asserts. When

the voltage rises above the specified high threshold fol-

lowing a 150ms (min) timeout period, the low-battery

output is deasserted. This ensures the supply voltage

has stabilized before power-converter or microproces-

sor activity is enabled.

These devices also have an independent µP supervisor

that monitors VCC and provides an active-low reset out-

put. A manual reset function is available to allow the

user to reset the µP with a pushbutton.

6 _______________________________________________________________________________________

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