User manual MAXIM MAX713

[. . . ] 19-0100; Rev 6; 12/08 KIT ATION EVALU ILABLE AVA NiCd/NiMH Battery Fast-Charge Controllers Features Fast-Charge NiMH or NiCd Batteries Voltage Slope, Temperature, and Timer Fast-Charge Cutoff Charge 1 to 16 Series Cells Supply Battery's Load While Charging (Linear Mode) Fast Charge from C/4 to 4C Rate C/16 Trickle-Charge Rate Automatically Switch from Fast to Trickle Charge Linear Mode Power Control 5µA (max) Drain on Battery when Not Charging 5V Shunt Regulator Powers External Logic General Description The MAX712/MAX713 fast-charge Nickel Metal Hydride (NiMH) and Nickel Cadmium (NiCd) batteries from a DC source at least 1. 5V higher than the maximum battery voltage. 1 to 16 series cells can be charged at rates up to 4C. A voltage-slope detecting analog-to-digital converter, timer, and temperature window comparator determine charge completion. The MAX712/MAX713 are powered by the DC source via an on-board +5V shunt regulator. [. . . ] Upon insertion of the battery (time 2), the MAX712/MAX713 detect current flow into the battery and switch to fast-charge state. Once full charge is detected, the device reverts to trickle charge (time 3). If the battery is removed (time 4), the MAX712/MAX713 remain in trickle charge and the output voltage is once again regulated as in time 1. battery pack is higher during a fast-charge cycle than while in trickle charge or while supplying a load. The voltage across some battery packs may approach 1. 9V/cell. The 1. 5V of overhead is needed to allow for worst-case voltage drops across the pass transistor (Q1 of Typical Q1 DC IN R2 R1 2N3904 D1 MAX712/MAX713 Powering the MAX712/MAX713 AC-to-DC wall-cube adapters typically consist of a transformer, a full-wave bridge rectifier, and a capacitor. Figures 10­12 show the characteristics of three consumer product wall cubes. All three exhibit substantial 120Hz output voltage ripple. When choosing an adapter for use with the MAX712/MAX713, make sure the lowest wall-cube voltage level during fast charge and full load is at least 1. 5V higher than the maximum battery voltage while being fast charged. Typically, the voltage on the V+ MAX712 MAX713 DRV Figure 5. DRV Pin Cascode Connection (for high DC IN voltage or to reduce MAX712/MAX713 power dissipation in linear mode) Table 4. MAX712/MAX713 Charge-State Transition Table POWER_ON_RESET 0 1 1 1 1 1 1 1 1 1 1 1 UNDER_VOLTAGE x 1 x x x 0 0 0 0 0 0 x x 0 x IN_REGULATION x x 1 x x 0 0 0 0 0 0 x x 0 x COLD x x x 0 x 1 1 1 1 1 0 x x x x HOT x x x x 0 1 1 1 1 1 1 x 0 x x Set trickle No change No change No change No change*** Set fast No change No change Set fast Set fast No change*** Set fast** Trickle to fast transition inhibited Trickle to fast transition inhibited Set trickle Set trickle Set trickle RESULT* Only two states exist: fast charge and trickle charge. * Regardless of the status of the other logic lines, a timeout or a voltage-slope detection will set trickle charge. ** If the battery is cold at power-up, the first rising edge on COLD will trigger fast charge; however, a second rising edge will have no effect. *** Batteries that are too hot when inserted (or when circuit is powered up) will not enter fast charge until they cool and power is recycled. _______________________________________________________________________________________ 9 NiCd/NiMH Battery Fast-Charge Controllers MAX712/MAX713 DC IN V+ REF DRV VLIMIT charge until one of the three fast-charge terminating conditions is triggered. If DC IN exceeds 20V, add a cascode connection in series with the DRV pin as shown in Figure 5 to prevent exceeding DRV's absolute maximum ratings. Select the current-limiting component (R1 or D4) to pass at least 5mA at the minimum DC IN voltage (see step 6 in the Getting Started section). The maximum current into V+ determines power dissipation in the MAX712/MAX713. maximum current into V+ = (maximum DC IN voltage - 5V)/R1 power dissipation due to shunt regulator = 5V x (maximum current into V+) Sink current into the DRV pin also causes power dissipation. Do not allow the total power dissipation to exceed the specifications shown in the Absolute Maximum Ratings. C2 D1 GND CELL_VOLTAGE CURRENT-SENSE AMPLIFIER PGM3 FAST_CHARGE Av X V+ OPEN REF BATT1 0 0 0 0 8 512 256 128 64 CC BATT- Fast Charge The MAX712/MAX713 enter the fast-charge state under one of the following conditions: 1) Upon application of power (batteries already installed), with battery current detection (i. e. , GND voltage is less than BATT- voltage), and TEMP higher than TLO and less than THI and cell voltage higher than the UVLO voltage. 2) Upon insertion of a battery, with TEMP higher than TLO and lower than THI and cell voltage higher than the UVLO voltage. [. . . ] Thermistors T2 and T3 can be replaced by standard resistors if absolute temperature charge cutoff is acceptable. All resistance values in Figures 9a and 9b should be chosen in the 10k to 500k range. MAX712/MAX713 __________Applications Information Battery-Charging Examples T2 MAX712 MAX713 BATTAMBIENT TEMPERATURE T3 0. 022F 1F NOTE: FOR ABSOLUTE TEMPERATURE CHARGE CUTOFF, T2 AND T3 CAN BE REPLACED BY STANDARD RESISTORS. Figures 13 and 14 show the results of charging 3 AA, 1000mAh, NiMH batteries from Gold Peak (part no. GP1000AAH, GP Batteries (619) 438-2202) at a 1A rate using the MAX712 and MAX713, respectively. The Typical Operating Circuit is used with Figure 9a's thermistor configuration . [. . . ]