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X3100 Datasheet(PDF) 5 Page - Intersil Corporation |
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X3100 Datasheet(HTML) 5 Page - Intersil Corporation |
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5 / 41 page  5 FN8110.1 January 3, 2008 Power to the X3100 or X3101 is applied to pin VCC via diodes D6 and D7. These diodes allow the device to be powered by the Li-Ion battery cells in normal operating conditions, and allow the device to be powered by an external source (such as a charger) via pin P+ when the battery cells are being charged. These diodes should have sufficient current and voltage ratings to handle both cases of battery cell charge and discharge. The operation of the voltage regulator is described in section “Voltage Regulator” on page 22. This regulator provides a 5VDC±0.5% output. The capacitor (C1) connected from RGO to ground provides some noise filtering on the RGO output. The recommended value is 0.1µF or less. The value chosen must allow VRGO to decay to 0.1V in 170ms or less when the X3100 or X3101 enter the sleep mode. If the decay is slower than this, a resistor (R1) can be placed in parallel with the capacitor. During an initial turn-on period (TPUR + TOC), VRGO has a stable, regulated output in the range of 5VDC ± 10% (see Figure ). The selection of the microcontroller should take this into consideration. At the end of this turn on period, the X3100 and X3101 “self-tunes” the output of the voltage regulator to 5V+/-0.5%. As such, VRGO can be used as a reference voltage for the A/D converter in the microcontroller. Repeated power-up operations, consistently re-apply the same “tuned” value for VRGO. Figure 1 shows a battery pack temperature sensor implemented as a simple resistive voltage divider, utilizing a thermistor (RT) and resistor (RT’). The voltage VT can be fed to the A/D input of a microcontroller and used to measure and monitor the temperature of the battery cells. RT’ should be chosen with consideration of the dynamic resistance range of RT as well as the input voltage range of the microcontroller A/D input. An output of the microcontroller can be used to turn on the thermistor divider to allow periodic turn-on of the sensor. This reduces power consumption since the resistor string is not always drawing current. Diode D3 is included to facilitate load monitoring in an Over- current protection mode (see section “Over-Current Protection” on page 19), while preventing the flow of current into pin OVP/LMON during normal operation. The N- Channel transistor turns off this function during the sleep mode. Resistor RPU is connected across the gate and drain of the charge FET (Q2). The discharge FET Q1 is turned off by the X3100 or X3101, and hence the voltage at pin OVP/LMON will be (at maximum) equal to the voltage of the battery terminal, minus one forward biased diode voltage drop (VP+ - VD7). Since the drain of Q2 is connected to a higher potential (VP+) a pull-up resistor (RPU) in the order of 1MΩ should be used to ensure that the charge FET is completely turned OFF when OVP/LMON = VCC. The capacitors on the VCELL1 to VCELL4 inputs are used in a first order low pass filter configuration, at the battery cell voltage monitoring inputs (VCELL1 - VCELL4) of the X3100 or X3101. This filter is used to block any unwanted interference signals from being inadvertently injected into the monitor inputs. These interference signals may result from: • Transients created at battery contacts when the battery pack is being connected/disconnected from the charger or the host. • Electrostatic discharge (ESD) from something/someone touching the battery contacts. • Unfiltered noise that exists in the host device. • RF signals which are induced into the battery pack from the surrounding environment. Such interference can cause the X3100 or X3101 to operate in an unpredictable manner, or in extreme cases, damage the device. As a guide, the capacitor should be in the order of 0.01µF and the resistor, should be in the order of 10k Ω . The capacitors should be of the ceramic type. In order to minimize interference, PCB tracks should be made as short and as wide as possible to reduce their impedance. The battery cells should also be placed as close to the X3100 or X3101 monitor inputs as possible. Resistors RCB and the associated n-channel MOSFET’s (Q6 - Q9) are used for battery cell voltage balancing. The X3100 and X3101 provide internal drive circuitry which allows the user to switch FETs Q6 - Q9 ON or OFF via the microcontroller and SPI port (see section “Cell Voltage Balance Control (CBC1-CBC4)” on page 12). When any of the these FETs are switched ON, a current, limited by resistor RCB, flows across the particular battery cell. In doing so, the user can control the voltage across each individual battery cell. This is important when using Li-Ion battery cells since imbalances in cell voltages can, in time, greatly reduce the usable capacity of the battery pack. Cell voltage balancing may be implemented in various ways, but is usually performed towards the end of cell charging (“Top-of- charge method”). Values for RCB will vary according to the specific application. The internal 4kbit EEPROM memory can be used to store the cell characteristics for implementing such functions as gas gauging, battery pack history, charge/discharge cycles, and minimum/maximum conditions. Battery pack manufacturing data as well as serial number information can also be stored in the EEPROM array. An SPI serial bus provides the communication link to the EEPROM. A current sense resistor (RSENSE) is used to measure and monitor the current flowing into/out of the battery terminals, and is used to protect the pack from over-current conditions (see section “Over-Current Protection” on page 19). RSENSE is also used to externally monitor current via a X3100, X3101 |
Similar Part No. - X3100_08 |
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Similar Description - X3100_08 |
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