MITSUMI Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357 Control of Lithium Ion Batteries (switching regulator secondary) (two cells) Monolithic IC MM1357 Outline This IC is used to control two-cell chargers and the secondary side of switching regulators; it features enhanced functions for current switching and for overcharge detection and other kinds of protection. The control output is capable of driving a photocoupler LED. The charging current can be switched between high and low currents, and each can also be varied externally. Features 1. Charging voltage 2. Charging current (switchable between high and low levels, variable) 3. Reference voltage Package SOP-14B Applications 1. Switching regulator 2. AC adapter 3. Lithium ion battery charger : Can be set externally High : 320mV typ. Low : 145mV typ. : 1.207V typ. Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357 MITSUMI Block Diagram Pin Assignment 14 13 12 11 10 9 1 2 3 4 5 SIP-14B 6 8 7 1 OUT 8 CC OUT 2 CFB 9 S-GND 3 CSR 10 VFB+ 4 CC IN 11 VCC 5 ADJ1 12 REG OUT 6 P-GND 13 VREF 7 ADJ2 14 VFB- Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357 MITSUMI Pin Description Pin no. Pin name Input/output 1 OUT Output 2 CFB Input 3 CSR Input 4 CC IN Input 5 ADJ1 Input 6 P-GND Input Function Output pin for charging control An external photocoupler is controlled for constant-current, constant-voltage charging control. Amp inverting input pin for current control An external capacitor (approx. 0.1 µF) is connected between CFB and OUT, and phase compensation used to improve oscillation. Current detection pin Current is detected via the voltage drop across an external resistance between CSR and GND (R1), to control the charging current. Charging current switching signal input pin H (VCC) is the charging current 0.15V/R1, and L (GND) is the charging current 0.32V/R1. If for instance R1 is 0.1Ω, then switching is between 1.5A and 3.2A (typ.). The switching voltage VTH is as follows. When REG OUT is 2.5V, VTH is 2.05V typ. When REG OUT is 4V, VTH is 3.0V typ. When REG OUT is 5V, VTH is 3.7V typ. Amp non-inverting input pin 1 for current control The pin voltage is set at 0.15V typ. With CC-IN at H or open, the non-inverting input pin of the current control amp is at 0.15 V. By adjusting the pin voltage using an external resistance or by other means, the charging current can be varied. Power ground pin Amp non-inverting input pin 2 for current control The pin voltage is set at 0.32V typ. With CC-IN at L, the non-inverting input pin of the current control amp is at 0.32V. By adjusting the pin voltage using an external resistance or by other means, the charging current can be varied. Charging current switching signal output pin Output is in phase with CC IN. By connecting an external capacitor between CC OUT and REG OUT, a delay can be added only when the current switching CC IN goes from H to L. For instance, when REG OUT is 4V, on connecting an 0.1µF capacitor CC OUT becomes about 50mS (an example is shown in the Timing Chart section). 7 ADJ2 Input 8 CC OUT Output 9 S-GND Input Signal ground pin 10 VFB+ Input Amp non-inverting input pin for voltage control The charging voltage is set through the resistances at the VFB + pin and the VFB - pin. 11 VCC Input Power supply input pin 12 REG OUT Output 13 VREF Input 14 VFB- Input Reference voltage circuit output pin The reference voltage can be set between 2 and 6V. The input current to start the reference voltage should be set to 1mA or greater. Reference voltage circuit input pin The VREF pin voltage is set at 1.2V typ. The REG OUT voltage can be set through the resistances between REG OUT and VREF, and between VREF and GND. Amp inverter input pin for voltage control Amp inverting input pin for voltage control The charging voltage can be set through the resistances at the VFB + pin and VFB - pin. By connecting an external capacitor (approx. 0.1µF) between VFB and OUT for phase compensation, oscillation can be improved. Absolute Maximun Ratings Item Storage temperature Operating temperature Power supply voltage Allowable loss Symbol TSTG TOPR VCC max. PD Ratings -40~+125 -20~+85 -0.3~+24 350 Units °C °C V mW Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357 MITSUMI Recommended Operating Conditions Item Operating temperature Operating voltage * Symbol TOPR VOPR Ratings -15~+80 +2~+20 * Units °C V The minimum operating voltage is under constant-current control Electrical Characteristics (Except where noted otherwise, Ta=25°C, REG OUT=4V, VCC=8.4V) Item VCC minimum input current Amp input for voltage control Input offset voltage Input bias current VFB+ Input bias current VFB- Symbol Measurement conditions Min. Typ. Max. Units ICC Excluding REG OUT input current 0.25 0.40 mA 1 20 20 VIO IB+ IB- Common-mode input voltage range * VI 0.7 5 mV 250 nA 250 nA REG OUT V -0.7 Amp input for current control ADJ1 pin input impedance RADJ1 13 kΩ 13 kΩ ADJ2 pin input impedance RADJ2 CFB pin input impedance RCFB 2 kΩ High-current mode 310 320 330 mV Current limit 1 VCL1 Current limit 2 VCL2 Low-current mode 137 145 153 mV OUT pin input current 1 IS1 OUT=8.4V (voltage-control amp) 20 mA OUT=4 V (voltage-control amp) 20 mA OUT pin input current 2 IS2 OUT=24V 2 µA OUT pin leakage current IL CC IN input impedance RCI 100 kΩ CC switching voltage L (VTR mode) VCL 2.6 V CC switching voltage H (CHG mode) VCH 3.4 V CC OUT output intake current ICO1 On switching from low to high current mode 6 µA 0.5 mA CC OUT output current ICO2 On switching from high to low current mode CC OUT output voltage range VCO 0.4 3.6 V Reference voltage VREF 1.195 1.207 1.219 V REG OUT output voltage variable range VREG 2.0 6.0 V 20 mA REG OUT maximum input current I max. 1.0 mA REG OUT minimum input current I min. Because there is an internal circuit for protection against shorts of external components, the common-mode input voltage range is 0.7V to REG OUT-0.7V. Values are set such that overvoltages do not occur when there is a short between VBF+ and REG OUT or between VFB- and GND. * Timing Chart Timing chart for connection of a timing capacitor CT to CC OUT With REG OUT at 4V and CT=0.1µF, TD is approx. 50mS. 8.4V VTH level CC-IN 0 4V CC-OUT VTH level 0 CSR 0.32V 0.15V TD CC IN VTH Low-current High-current CC OUT mode mode VTH Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357 MITSUMI Application Circuits Note 1 : 1. The REG OUT voltage can be set to 1.2V typ. (R5+R6)/R6. (REG OUT = 2 to 6V) 2. The value of R4 should be set according to the load. (Consider it to be a shunt regulator.) 3. The voltage under constant-voltage charging is equal to (R3/R2) REG OUT. When a highprecision voltage is required, use the knob for adjustment. 4. The current in constant-current charging can be set to either of two values, 0.15V/R1 (when CC-IN is H), and 0.32V/R1 (when CC-IN is L). 5. R7 is a resistance for current limiting. 6. The capacitors C1 and C5 are to prevent oscillation; C4 is for soft starting of the REG OUT voltage; and C2 is used to delay current switching (CC-OUT switched from H to L). Note 2 : This IC incorporates a voltage-controlling amp and protection against shorting to VREF ; when R2, R3, R5 and R6 are shorted, the voltage is limited to its minimum value. By means of a comparator within the VFB+, VFB- and VREF pin area, upon resistance shorting the OUT pin is forced to L. Note 3 : The above diagram is an example for reference purposes; in actual use the circuit should be studied thoroughly prior to use. Characteristics Current limit 1 vs temperature Current limit 2 vs temperature 0.2 Current limit 2 (V) Current limit 1 (V) 0.35 0.3 0.25 -25 0 25 50 Ambient temperature (°C) 75 85 0.15 0.1 -25 0 25 50 Ambient temperature (°C) 75 85 Control of Lithium Ion Batteries (switching regulator secondary) (two cells) MM1357 MITSUMI REG OUT voltage (4V)- temperature REG OUT voltage (4V) (V) Reference voltage vs temperature Reference voltage (V) 1.22 1.21 1.2 -25 0 25 50 75 85 4.05 REG OUT input current10mA 4 3.95 -25 3.5 CC IN, H 2.5 -25 0 H L 25 50 CC IN, L 4 2 CC IN, H CT=0.1µF CC OUT (V) CT=0µF CT=0.047µF 2 1 0 -1 0 20 40 60 80 100 120 0 2 3 REG OUT voltage (V) 4 3 2 1 REG OUT input current (mA) 100 6 8 6 4 2 0 -25 0 25 50 Ambient temperature (°C) 5 10 5 10 REG OUT voltage vs REG OUT input current Ta=25°C 1 4 CC OUT intake current vs temperature TIME (mS) 0 0.1 L 1 REG OUT voltage (V) CC OUT intake current (µA) 5 H 3 75 85 CC OUT-DELAY TIME Ta=25°C REG OUT=4V (CT is the capacitance between CC OUT and REG OUT) 3 75 85 5 Ambient temperature (°C) 4 50 CC switching voltage vs REG OUT voltage CC switching voltage (V) CC switching voltage (V) CC switching voltage vs temperature REG OUT=4V 3 25 Ambient temperature (°C) Ambient temperature (°C) CC IN, L 0 75 85