Datasheet LT1510, LT1510-5 (Analog Devices) - 8

LT1510/LT1510-5
TEST CIRCUITS Test Circuit 2
LT1510 OVP + VA – VREF PROG I 10k PROG 10k – LT1013 + + 0.47µF RPROG 2.465V 1510 TC02
U OPERATIO
The LT1510 is a current mode PWM step-down (buck) level shift resistors R2 and R3, forming the current mode switcher. The battery DC charging current is programmed inner loop. The Boost pin drives the switch NPN QSW into by a resistor RPROG (or a DAC output current) at the PROG saturation and reduces power loss. For batteries like pin (see Block Diagram). Amplifier CA1 converts the lithium-ion that require both constant-current and con- charging current through RS1 to a much lower current stant-voltage charging, the 0.5%, 2.465V reference and IPROG (500µA/A) fed into the PROG pin. Amplifier CA2 the amplifier VA reduce the charging current when battery compares the output of CA1 with the programmed current voltage reaches the preset level. For NiMH and NiCd, VA and drives the PWM loop to force them to be equal. High can be used for overvoltage protection. When input volt- DC accuracy is achieved with averaging capacitor CPROG. age is not present, the charger goes into low current (3µA Note that IPROG has both AC and DC components. IPROG typically) sleep mode as input drops down to 0.7V below goes through R1 and generates a ramp signal that is fed to battery voltage. To shut down the charger, simply pull the the PWM control comparator C1 through buffer B1 and VC pin low with a transistor.
U U W U APPLICATIONS INFORMATION
Application Note 68, the LT1510 design manual, contains tantalum capacitors such as the AVX TPS and Sprague more in depth appications examples. 593D series have high ripple current rating in a relatively small surface mount package, but caution must be used
Input and Output Capacitors
when tantalum capacitors are used for input bypass. High In the chargers in Figures 1 and 2 on the first page of this input surge currents can be created when the adapter is data sheet, the input capacitor C hot-plugged to the charger and solid tantalum capacitors IN is assumed to absorb all input switching ripple current in the converter, so it must have a known failure mechanism when subjected to very have adequate ripple current rating. Worst-case RMS high turn-on surge currents. Highest possible voltage ripple current will be equal to one half of output charging rating on the capacitor will minimize problems. Consult with current. Actual capacitance value is not critical. Solid the manufacturer before use. Alternatives include new high 8