Datasheet MAX6846, MAX6847, MAX6848, MAX6849 (Maxim) - 6

Low-Power, Adjustable Battery Monitors with Hysteresis and Integrated µP Reset Pin Description PIN NAME FUNCTION MAX6846/MAX6847 MAX6848/MAX6849
1 1 VDD VDD Supply. Device power supply if VDD is greater than VCC. 2 2 GND Ground LTH Threshold Monitor Input. A resistor-divider network sets the low 3 3 LTHIN threshold associated with LBOL and LBO. Low-Battery Output, Active-Low, Open-Drain. LBO is asserted when LTHIN 4 — LBO 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 5 5 RESET timeout period when the MR input is pulled low. RESET is an open-drain
MAX6846–MAX6849
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. 6 — MR Leave unconnected or connect to VCC if unused. The MR input is debounced for MR rising edges to prevent false reset events. HTH Threshold Monitor Input. A resistor-divider network sets the high 7 7 HTHIN threshold associated with LBOH and LBO. V 8 8 V CC Voltage Input. Input for VCC reset threshold monitor and device power CC 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
adjustable thresholds are ideal for monitoring single- cell Li+ or multicell alkaline/NiCd/NiMH power supplies. The MAX6846–MAX6849 family is available with several monitoring options. The MAX6846/MAX6847 have single When the power-supply voltage drops below the speci- low-battery outputs and the MAX6848/MAX6849 have fied low threshold, the low-battery output asserts. When dual low-battery outputs (see Figures 1a and 1b). the voltage rises above the specified high threshold fol- lowing a 150ms (min) timeout period, the low-battery The MAX6846–MAX6849 combine a 615mV reference output is deasserted. This ensures the supply voltage with two comparators, logic, and timing circuitry to pro- has stabilized before power-converter or microproces- vide the user with information about the charge state of sor activity is enabled. the power-supply batteries. The MAX6848/MAX6849 monitor separate high-voltage and low-voltage thresh- These devices also have an independent µP supervisor olds to determine battery status. The output(s) can be that monitors VCC and provides an active-low reset out- used to signal when the battery is charged, when the put. A manual reset function is available to allow the battery is low, and when the battery is empty. User- user to reset the µP with a pushbutton.
6 _______________________________________________________________________________________