Datasheet LTC4006 (Analog Devices) - 9

LTC4006
U OPERATIO Table 1. Truth Table for LTC4006 Operation MODE DCIN BAT VOLTAGE BAT CURRENT ACP/SHDN TIMER STATE CHG*
Shut Down by Low Adapter Voltage <BAT >UVLO Leakage LOW Reset HIGH Conditioning a Depleted Battery >BAT <2.5V/Cell 10% Programmed HIGH Running LOW Current Normal Charging >BAT >2.5V/Cell Programmed HIGH Running LOW Current Input Current Limited Charging >BAT >2.5V/Cell Programmed HIGH Running LOW Current Charger Paused Due to Thermistor Out of Range >BAT X OFF HIGH Paused LOW or 25µA (Faulted) Shut Down by ACP/SHDN Pin >BAT X OFF Forced LOW Reset HIGH Terminated by Low-Battery Fault (Note 1) >BAT <2.5V/Cell OFF HIGH >T/4 Stopped HIGH (Faulted) Top-Off Charging. C/10 is Latched >BAT VFLOAT OFF HIGH <T/4 After C/10 25µA Comparator Trip. Running Timer is Reset by C/10 Comparator (Latched), >BAT VFLOAT OFF HIGH >T/4 After C/10 HIGH then Terminates After 1/4 T Comparator Trip. (Waiting Stopped for Restart) Terminated by Expired Timer >BAT VFLOAT** OFF HIGH >T Stopped HIGH (Waiting for Restart) Timer Defeated. (Low-Battery Conditioning Still X X X X X Forced LOW Functional) Shut Down by Undervoltage Lockout >BAT <UVL OFF HIGH Reset HIGH** and <UVL Timer Defeated Until VBAT > 3.9V/Cell >BAT 2.5V ≤ VBAT ≤3.9V Programmed HIGH Running LOW (V/Cell) Current *Open Drain. High when used with pull-up resistor.
Note 1:
If a depleted battery is inserted while the charger is in this state, **Most probable condition, X = Don’t care the charger must be reset to initiate charging. compares this current against the desired current programmed The accuracy of VIMON will range from 0% to ITOL. by RIMON at the IMON pin and adjusts ITH until: VIMON is plotted in Figure 2. V V – V . 11 67 A • k REF CSP BAT = + µ 3 Ω The amplifier CL1 monitors and limits the input current to R k IMON 3 Ω a preset level (100mV/RCL). At input current limit, CL1 will decrease the I therefore, TH voltage, thereby reducing charging cur- rent. When this condition is detected, the C/10 indicator will ⎛ V ⎞ k 3 Ω I REF = – . 11 67 A 1.2 CHARGE µ • ⎝⎜R ⎠⎟ R 1.19V IMON SENSE 1.0 The voltage at BAT is divided down by an internal resistor 0.8 divider and is used by error amp EA to decrease ITH if the (V) 0.6 divider voltage is above the 1.19V reference. When the IMONV charging current begins to decrease, the voltage at IMON 0.4 will decrease in direct proportion. The voltage at IMON is 0.309V 0.2 then given by: 0 R 0 20 40 60 80 100 V = I( •R + 11.67 A µ • k IMON 3 ) ICHARGE (% OF MAXIMUM CURRENT) IMON CHARGE SENSE Ω • k3Ω 4006 F02
Figure 2. VIMON vs ICHARGE
4006fa 9