ltc4150库伦检测

这个是LTC4150 库仑计芯片手册，里面有典型应用，可以直接按图搭建电路，结合单片机就可以检测锂电池的电量了。
元器件交易网www.cecb2bcom LTC4150 ELECTRICAL CHARACTERISTICS Note 1: Absolute Maximum Ratings are those values beyond which the life Note 3: Measured at least 20ms after power or of a device may be impaired Note 4: Tested in feedback loop to SENSEt and SENSE Note 2: Guaranteed by design and not tested in production TYPICAL PERFORMAnCE CHARACTERISTICS (Specifications are at TA=25C,unless otherwise noted. Voltage to Frequency Gain Voltage to Frequency Gain vS Supply Voltage vS Temperature Operating lpD vs vi 1.00 +1.00 140 SENSE= 50mV .75 +0.50 二+0.25 025 2.7V VSENSE=25mV Von=8.5V 臣025 VsENSE 50mV 0.50 -050 -0.75 0.75 100 DD(V) TEMPERATURE (C) 4150601 4150G02 4150603 dervoltage Lockout Threshold Shutdown Ipp vs vpp Digital Output Low voltage vS V vS Temperature 400 OL=1.6mA 2.60 RISING EDGE 2.59 300 2.58 POL PIN 2.57 200 FINT PIN 2.56 2.53 23456789 -50-250255075100125 TEMPERATURE(°C) 4150304 4150G05 4150e06 LINEAR TECHNOL○G 3 元器件交易网www.cecb2bcom LTC4150 PIn FUnCtIons SENSEt (Pin 1): Positive Sense Input. This is the POL (Pin 6): Battery current Polarity Open-Drain Output noninverting current sense input. Connect SENSEt to the POL indicates the most recent battery current polarity load and charger side of the sense resistor. Full-scale When INT is high. a low state indicates the current is current sense input is 50mV. SENSEt must be within flowing out of the battery while high impedance means the 60mv of vop for proper operation current is going into the battery. POL latches its state when is asserted low. PoL is an open-drain output and can SENSE(Pin 2 ) Negative Sense nput. This is the inverting be pulled up to any logic supply up to 9V In shutdown current sense input. Connect senSe- to the positive battery terminal side of the sense resistor. Full-scale pol is high impedance current sense input is 50mV. SENSE must be within GND(Pin 7): Ground. Connect directly to the negative 60mv of VpD for proper operation battery terminal CF+(Pin 3): Filter Capacitor Positive Input. A capacitor Vpp(Pin 8): Positive Power Supply Connect to the load connected between Ct and CF filters and averages noise and charger side of the sense resistor. SENSE also and fast battery current variations. A4.7uF value is recom- connects to VDD. VDD operating range is 2. 7V to 8.5V mended. If filtering is not desired, leave Ct and ce Bypass vdp with 4.7uF capacitor unconnected CLR (Pin 9): Clear Interrupt Digital Input. When asserted F(Pin 4 Filter Capacitor Negative Input. a capacitor low for more than 20us, Clr resets INT high. Charge connected between CF* and CF filters and averages noise counting is unaffected. INT may be directly connected to and fast battery current variations. A 4.7uF value is recom- CLR. In this case the LtC4150 will capture each assertion mended. If filtering is not desired, leave Ct and ce of iNT and wait at least 1 us before resetting it. This ensures unconnected that INT pulses low for at least 1us but gives automatIc INT SHDN(Pin 5 Shutdown Digital Input When asserted reset In applications with a logic supply Vcc VDD, a low Shdn forces the ltC4150 into its low current con sumption power-down mode and resets the part. In appli- the Applications Information section cations with logic supply v cc>VDD, a resistive divider INT (Pin 10): Charge Count Interrupt Open-Drain Output must be used between SHDN and the logic which drives it. INT latches low every 1/VsensE. GvE) seconds and is See the applications Information section reset by a low pulse at CLR. INT is an open-drain output and can be pulled up to any logic supply of up to 9V. In shutdown INT is high impedance 4 LINEAR 元器件交易网www.cecb2bcom LTC4150 BLOCK DIAGRA CHARGER LOAD REFHI 17v SENSE+ 100pF 200k COUNTER □cR AMPLIFIER CONTROL LOGIC CHARGE CF C DISCHARGE REFO 95V -SHDN GND Figure 1 Block Diagram TImInG DIaGRAms CLR 50 OCo tCLR 0%50% INT 4150F02 Figure 2. CLR Pulse Width to Reset INT Figure 3 INT Minimum Pulse Width, CLR and INT Connected CLR and int Not connected LNEAR 5 元器件交易网www.cecb2bcom LTC4150 OPERATIOn Charge is the time integral of current. The LTC4150 CHARGE COUNTING measures battery current by monitoring the voltage devel- oped across a sense resistor and then integrates this First, the current measurement is filtered by capacitor cp information in several stages to infer charge. The block connected across pins cet and CF. this averages fast Diagram shows the stages described below. As each unit changes in current arising from ripple, noise and spikes in of charge passes into or out of the battery, the LTC4150 the load or charging current IT pin interrupts an external microcontroller and the POL Second, the filter's output is applied to an integrator with IN pin reports the polarity of the charge unit The external the amplifier and 100pF capacitor at its core. When the microcontroller then resets INT with the CLR input in integrator output ramps to REFHlor REFLOlevels, switches preparation for the next interrupt issued by the LTC4150. S1 and S2 reverse the ramp direction. By observing the The value of each charge unit is determined by the sense condition of si and S2 and the ramp direction, polarity is resistor value and the sense voltage to interupt frequency determined. The integrating interval is trimmed to 600us gain gvE of the LTC4150 at 50mv full-scale sense voltage Power-On and start-Up Initialization Third, a counter is incremented or decremented every time the integrator changes ramp direction. The counter effec When power is first applied to the tc4150 all internal tively increases integration time by a factor of 1024, circuitry is reset. After an initialization interval, the ltC4150 greatly reducing microcontroller overhead required to begins counting charge. This interval depends on Vpp and service interrupts from the LTC4150 the voltage across the sense resistor but will be at least At each counter under or overflow the iNt output latches 5ms. It may take an additional 80ms for the LTC4150 to low, flagging a microcontroller. Simultaneously the pOl accurately track the sense voltage. An internal undervolt- output is latched to indicate the polarity of the observed age lockout circuit monitors Vpp and resets all circuitry charge. With this information, the microcontroller can When Von falls below 2.5V total the charge over long periods of time, developing an Asserting SHDN low also resets the LTC4150's internal accurate estimate of the battery's condition. Once the circuitry and reduces the supply current to 1.5uA In this interrupt is recognized, the microcontroller resets INT condition, PoL and int outputs are high impedance The with a low going pulse on clr and awaits the next LTC4150 resumes counting after another initialization interrupt. Alternatively, iNT can drive clr interval. Shutdown minimizes battery drain when both the charger and load are off 人/LA 元器件交易网www.cecb2bcom LTC4150 APPLICATIONS IOFORIG。n SENSE VOLTAGE INPUT AND FILTERS Coulomb Counting Since the overall integration time is set by internally The ltC4150's transfer function is quantified as a voltage trimming the LTC4150, no external timing capacitor or to frequency gain GVE, where output frequency is the trimming is necessary. The only external component that number of interrupts per second and input voltage is the affects the transfer function of interrupts per coulomb of differential drive vsense acroSs sEnSe and SeNse. The charge is the sense resistor, Rsense. The common mode number of interrupts per second will be range for the SENSEt and SENSE- pins is VDD+60mV, with f= gy a maximum differential voltage range of +50mV. SENSE+ 3VF° V SENSE is normally tied to Vpp, so there is no common mode issue where hen SENSE operates within the 50mv differential limit VSENSE IBATTERY. RseNSE relative to sense Therefore Choose rsense to provide 50mv drop at maximum charge or discharge current, whichever is greater. Calculate rseNsI /F°| BATTERY RSENSE rom Since I.t=Q, coulombs of battery charge per INt pulse 50mv can be derived from Equation 4 R sense One INt Coulombs The sense input range is small (=50mv) to minimize the UVF° RsENSE loss across RSENSE. To preserve accuracy, use Kelvin Battery capacity is most often expressed in ampere-hours connections at rsense 1Ah= 3600 Coulombs (6) The external filter capacitor CF operates against a total on chip resistance of 4k to form a lowpass filter that averages Combining equations 5 and 6 battery current and improves accuracy in the presence ot noise, spikes and ripple. 4.7uf is recommended for gen One INT eral applications but can be extended to higher values as 3600·G VERSENSE long as the capacitors leakage is low. A 1OnA leakage is or roughly equivalent to the input offset error of the integra- tor. Ceramic capacitors are suitable for this use 1Ah=3600·GV° RSENSE Interrupts Switching regulators are a particular concern because The charge measurement may be further scaled within the they generate high levels of current ripple which may flow microcontroller. However, the number of interrupts, cou through the battery. The Vpp and sENSe connection to lombs or Ah all represent battery charge the charger and load should be bypassed by at least 4.7uf The LTC4150's transfer function is set only by the value of at the LtC4150 if a switching regulator is present the sense resistor and the gain GVE. Once RsensE is The LtC4150 maintains high accuracy even when burst selected using equation 1, the charge per interrupt can be Mode switching regulators are used. Burst pulse"on determined from Equation 5 or 7 levels must be within the specified differential input volt- Note that rsense is not chosen to set the relationship age range of 50mv as measured at CF* and CF To retain between ampere- hours of battery charge and number of accurate charge intormation, the LtC4 150 must remain interrupts issued by the LtC4150. Rather, rsense iS enabled during Burst Mode operation. If the LtC4150 chosen to keep the maximum sense voltage equal to or shuts down or VDD drops below 2.5V, the part resets and less than the LTC4150's 50mv full-scale sense input charge intormation is lost Burst Mode is registered trademark of Linear Technology Corporation 4150fa LNEAR 元器件交易网www.cecb2bcom LTC4150 APPLICATIOnS FORmGTIOn INT POL and clr Interfacing to INT, POL, CLR and shdn NT asserts low each time the LTC4150 measures a unit of The ltC4150 operates directly from the battery while in charge. At the same time, POL is latched to indicate the most cases the microcontroller supply comes from some polarity of the charge unit. The integrator and counter separate, regulated source. This poses no problem for INT continue running so the microcontroller must service and and pol because they are open-drain outputs and can be clear the interrupt before another unit of charge accumu- pulled up to any voltage 9v or less, regardless of the lates. Otherwise, one measurement will be lost. The time voltage applied to the LtC4150'S VoD available between interrupts is the reciprocal of CLR and shdn inputs require special attention to drive Equation 2 them, the microcontroller or external logic must generate a minimum logic high level of 1.9V. The maximum input Time per INT Assertion (9) level for these pins is VDD+.3v. If the microcontroller's VVE ENSe supply is more than this, resistive dividers must be used At 50mV full scale, the minimum time available is 596ms. on CLR and SHDN. The schematic in Figure 6 shows an o be conservative and accommodate for small. unex- application with InT driving CLR and microcontroller V( pected excursions above the 50mV sense voltage limit, the >VDD. The resistive dividers on clr and shdn keep the microcontroller should process the interrupt and polarity voltages at these pins within the LTC4150's VpD range information and clear int within 500ms Choose r2 and r1 so that Toggling CLR low for at least 20us resets INT high and (1 R2)250RL (12) unlatches POL. Since the LTC4150's integrator and counter operate independently of the INT and POL latches, no 1.9vs R1 charge information is lost during the latched period or R1+R2 CC s DD Minimum (13) while CLr is low. Charge/ discharge information continues Equation 13 also applies to the selection of R3 and R4.The tO accumulate during those intervals and accuracy is minimum vpp is the lowest supply to the ltC4150 when unaffected the battery powering it is at its lowest discharged voltage Once cleared, INT idles in a high state and pOl indicates When the battery is removed in any application, the clr eal-time polarity of the battery current. POL hi nigh indi- and SHDN inputs are unpredictable. INT and POL outputs cates charge flowing into the battery and low indicates may be erratic and should be ignored until after the battery charge flowing out. Indication of a polarity change re- is replaced quires at least If desired, the simple logic of Figure 4 may be used to derive separate charge and discharge pulse trains from tp-GivF·1024W (10) INT and POL SENSE here vsense is the smallest sense voltage magnitude T CHARGE before and after the polarity change CLR Open-drain outputs POL and int can sink loL=1.6mA at LTC4150 Vol=0.5V. The minimum pull-up resistance for these pins ISCHARGE should be RL>(cc-05)/16mA 4150「04 where vcc is the logic supply voltage. Because speed isn't Figure 4. Unravelling Polarity-- an issue, pull-up resistors of 1 ok or higher are adequate Separate Charge and Discharge Outputs 4150fa LINEAR 元器件交易网www.cecb2bcom LTC4150 APPLICATIONS IOFORIG。n AUTOMATIC CHARGE COUNT INTERRUPT AND CLEAR the battery Vpp, use Figure 6. The resistor dividers on cLr and shdn keep the voltages at these pins within the In applications where a ClR pulse is unavailable, it's easy LTC4150'sDD range. Choose an rl value using Equation tO make the LtC4150 run autonomously, as shown in Figures 5 and 6. If the microcontroller vcc is less than or 11 and r1-R4 values using Equation 13. In either applica equal to the battery VDD, INT may be directly connected to tion the LtC4150 will capture the first assertion of INT and CLR, as in Figure 5. The only requirement is that the wait at least 1us before resetting it. This insures that INT microcontroller should be able to provide a high logic level pulses low for at least 1us but gives automatic /NT reset of 1.9Vto SHDN If the microcontroller vcc is greater than POWER-DOWN SWITCH PROCESSOR C 工E47rF S SRL SENSE LTC4150 CLR NSE 27VT085+ GND C 4.7uF POL Figure 5. Application with INT Direct Drive of CLR and Separate Microprocessor Supply vcc s vpp POWER-DOWN SWITCH LOAD PROCESSOR F RL2 RL INT LTC4150 CLR BATTERY 4.7uF GND VBAITERY&VcC ( uF C SHDN POL SHUTDOWN R3 Figure 6. Application with INT Driving CLR and separate Microprocessor Supply vcc>vpp LINEAR TECHNOL○G 9 元器件交易网www.cecb2bcom LTC4150 APPLICATIOnS FORmGTIOn PC BOARD LAYOUT SUGGESTIONS TO CHARGER eep all traces as short as possible to minimize noise and inaccuracy. The supply bypass capacitor C2 should be PIN placed close to the LTC4150 The 4.7uF filter capacitor Cp ENSE LTC4150 should be placed close the Cat and CF pins and should be a low leakage, unpolarized type. Use a 4-wire Kelvin sense connection for the sense resistor, locating it close to the LTC4150 With short sense traces to the sense and TO BATTERY SENSE pins and longer force lines to the battery pack and Figure 7. Kelvin Connection on SENSE Resistor powered load, see Figure 7 TYPICAL APPLICATIOnS Figure 8 shows a typical application designed for a single With a microcontroller supply =5v, equation 11 gives cell lithium-ion battery and 500mA maximum load current. Rl>2.875k. The nearest standard value is 3k Use equation 1 to calculate RsENSE=0.05V/0.5A=0.1Q2 From Equation 12, Rl= 3k gives r1 r2 equal to 1505k With re SENSE=0.1 Q, Equation 7 shows that each interrupt A single cell lithium-ion battery can discharge as low as corresponds to 0.085mAh. Equation 14, derived from 2.7V Equation 2, gives the number of int assertions for average From Equation 13, select R1=75k; the nearest standard battery current, IBATT, over a time, t, in seconds value for r2 is 76.8k NT Assertions=GvF·lBAT° RSENSE.t (14) Also from Equation 13, we choose R3 75k and R4 Loading the battery so that 515ma is drawn from it over 768k 600 seconds results in 100 int assertions For an 800mAh battery, this is (515mA. 1/6h)/800mAh=11% of the batterys capacity POWER-DOWN SWITCH 50V RL R SENSE+ SENSE LTC4150 CLR 76.8k SENSE DD SINGLE-CELL GND R1 3.0V~42V 4.7uF SHUTDOWN 768k R3 Figure 8. Typical Application, Single Cell Lithium-lon Battery 10 人/LA