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Technical content

Features

 Precise Reset Threshold: ±2%  Hysteresis to Eliminate the Output Chatter  CMOS Output  60ms typical Delay to Filter out the noise  1.8µA Supply Current @VCC=3V  Guaranteed Output Valid to VCC = +1.15V  Power Supply Transient Immunity  Operating Temperature Range -40°C to +85°C  Available in SOT23-5 Pin Assignment VCC NC LBO GND CN301 3 4 LBI Typical Application Circuit CN301 LBO VBAT LBI VCC GND Figure 1 Monitoring Battery Voltage Lower Than 6V

1.9V to 6V Figure 2 Monitoring Battery Voltage Higher Than 6V Pin Description Pin No. Symbol Description

1 GND Negative Terminal of Power Supply(Ground)

2 VCC Positive Terminal of Power Supply. This pin is the power supply to internal circuit.

3 LBO

Low Battery Output. CMOS output. If the voltage at LBI pin is higher than the rising threshold for more than 60ms typical, LBO will transition to high; If the voltage at LBI pin is lower than the falling threshold, LBO will transition to low.

4 LBI

Low Battery Input. The voltage that needs to be monitored is sensed at this pin. Generally LBI pin should be tied to an external resistor divider to sense the battery voltage. 5 NC No Connection. ABSOLUTE MAXIMUM RATINGS Terminal Voltage (With respect to GND) Input/Output Current Stresses beyond those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.

Electrical Characteristics

(VCC=3V , TA= －40℃ to 85 ℃, Typical values are at TA=25℃, unless otherwise noted.) Parameters Symbol Test Conditions M i n T y p M a x U n i t Operating V oltage Range VCC 1 . 9 6 V VCC=3.0V 1 1 . 8 4 Operating Current I VCC VCC=5.0V 1 2 . 0 4 . 2 uA Rising Threshold Vrth LBI pin voltage rising 1.196 1.22 1.244 Falling Threshold V fth LBI pin voltage falling 1.105 1.14 1.175 V LBI Pin Bias Current I LBI －100 0 100 nA TC of Rising Threshold TC1 －40℃ to 85 ℃ －1 0 0 ＋100 ppm TC of falling Threshold TC2 －40℃ to 85 ℃ －800 ppm t1 LBI pin voltage rising 30 60 100 ms LBI to LBO Delay t2 LBI pin voltage falling 20 us VCC=2V , VLBI＝0V ISINK=1.5mA 0.3 VCC=3V , VLBI＝0V ISINK=3.2mA 0 . 3 LBO Low V oltage VOL VCC=5V , VLBI＝0V ISINK=6mA 0 . 3 V VCC=2V , VLBI＝1.5V ISOURCE=1.5mA VCC-0.4 VCC=3V , VLBI＝1.5V ISOURCE=3mA VCC-0.4 LBO High V oltage VOH VCC=5V , VLBI＝1.5V ISOURCE=5mA VCC-0.4 V Detailed Description CN301 is an ultra low power battery monitor, if the voltage at LBI pin falls below the falling threshold, LBO will become low after a short delay(20us typical); If the voltage at LBI pin goes higher than the rising threshold, LBO will become high after a delay of 60ms typical, the delay can filter out the noise or any disturbance on the monitored voltage caused by the load switch on or switch off, so the system reliability is enhanced. The difference between rising threshold and falling threshold is also called hysteresis, which can

provide noise immunity and remove the possibility of output chatter due to battery terminal voltage recovery after the load removal. CN301 is specially designed for monitoring single or multi lithium-ion (Li+) cells, multi-cell alkaline, NiCd, NiMH and multi-cell lead acid batteries. The operation of the device can be best understood by referring to figure 3. LBI Vdown Vup LBO Figure 3 Timing waveform Applications Information R1 and R2 Selection LBI pin senses the battery voltage via the resistor divider formed by R1 and R2 in Figure 1 and Figure 2. Choosing the proper R1 and R2 values is a balance between accuracy and power consumption. The leakage current into LBI pin travels through the resistor divider and introduce an error, If extremely high resistor values are used, the leakage current introduces a significant error; While with extremely low resistor values, the error becomes negligible, but the resistive divider draws more power from the battery than necessary and shortens battery life. The battery voltage at which LBO should activate is calculated by the following equation: Where, I LBI is the leakage current into LBI pin Vrth is the rising threshold From the above equation, if ILBI＝5nA, R1＝2MΩ, then the error is about 10mV So the maximum R1 value should be decided by the acceptable error, and the minimum value should be decided by the battery power consumption due to R1 and R2’s presence. Adding External Capacitance to Enhance Noise Immunity If monitoring voltages in a noisy environment, add a bypass capacitor of 0.1μF from battery terminal to GND as close as possible to the device. For systems with large transients, additional capacitance may be required. A small capacitor (<1nF) from LBI pin to GND may provide additional noise immunity. Negative-Going LBI Transients In addition to issuing a low output at LBO pin during power-up, power-down, and brownout conditions of the monitored voltage, the CN301 is relatively immune to short-duration negative-going LBI transients (glitches). As the magnitude of the transient increases (goes farther below the down trip point), the maximum allowable pulse width decreases. Typically, a LBI transient that goes 35mV below the down trip point and lasts 10µs or less will not cause a low LBO output. A bypass capacitor from LBI pin to GND provides additional transient immunity.

Choose the Power Supply for CN301 If the battery voltage is greater than 6V , CN301 can not be directly powered by the battery. In this case if there is a power supply that is from 1.9V to 6V in the system, then CN301 can be powered by this power supply, otherwise the circuit in Figure 9 can be used to generate the power supply for CN301. In Figure 9, resistor R3 and R4 are used to generate a voltage between 1.9V to 6V to power CN301. R3 and R4 should be chosen in such a way that the current flowing through R3 is larger than 5uA to meet CN301’s current consumption, also R3 and R4 can not load the battery too much. A 1uF capacitor can be chosen for C1. CN301 VCC GND LBI LBO battery voltage more than 6V R4 C1 Figure 9 Power CN301 from a Resistor Divider

Package Information

Consonance does not assume any responsibility for use of any circuitry described. Consonance reserves the right to change the circuitry and specifications without notice at any time.