Datasheet LT1769 (Analog Devices) - 8
| Manufacturer | Analog Devices |
| Description | Constant-Current/Constant-Voltage 2A Battery Charger with Input Current Limiting |
| Pages / Page | 16 / 8 — TEST CIRCUITS. Test Circuit 1. Test Circuit 2. OPERATION |
| File Format / Size | PDF / 243 Kb |
| Document Language | English |
TEST CIRCUITS. Test Circuit 1. Test Circuit 2. OPERATION
Model Line for this Datasheet
Text Version of Document
LT1769
TEST CIRCUITS Test Circuit 1
SPIN LT1769 RS3 – SENSE 200Ω + VC R R S1 CA2 CA1 S2 100Ω + BAT 200Ω 1k 0.047 60k – µF + VBAT VREF PROG 1µF 300Ω RPROG + LT1006 1k 1769 TC01 – + ≈ 0.65V 20k
Test Circuit 2
LT1769 OVP + VA – V PROG REF 10k IPROG 10k – LT1013 + + 0.47µF RPROG 2.465V 1769 TC02
U OPERATION
The LT1769 is a current mode PWM step-down (buck) shift resistors R2 and R3, forming the current mode inner switcher. The battery DC charge current is programmed 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- charge current through RS1 to a much lower current IPROG stant-voltage charging, the 0.5%, 2.465V reference and fed into the PROG pin. Amplifier CA2 compares the output the amplifier VA reduce the charge current when battery of CA1 with the programmed current and drives the PWM voltage reaches the preset level. For NiMH and NiCd, VA control loop to force them to be equal. High DC accuracy can be used for overvoltage protection. When the input is achieved with averaging capacitor CPROG. Note that voltage is removed, the VCC pin drops to 0.7V below the IPROG has both AC and DC components. IPROG goes battery voltage, forcing the charger into a low battery drain through R1 and generates a ramp signal that is fed to the (3µA typical) sleep mode. To shut down the charger, PWM control comparator C1 through buffer B1 and level simply pull the VC pin low with a transistor. 1769fa 8
TEST CIRCUITS Test Circuit 1
SPIN LT1769 RS3 – SENSE 200Ω + VC R R S1 CA2 CA1 S2 100Ω + BAT 200Ω 1k 0.047 60k – µF + VBAT VREF PROG 1µF 300Ω RPROG + LT1006 1k 1769 TC01 – + ≈ 0.65V 20k
Test Circuit 2
LT1769 OVP + VA – V PROG REF 10k IPROG 10k – LT1013 + + 0.47µF RPROG 2.465V 1769 TC02
U OPERATION
The LT1769 is a current mode PWM step-down (buck) shift resistors R2 and R3, forming the current mode inner switcher. The battery DC charge current is programmed 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- charge current through RS1 to a much lower current IPROG stant-voltage charging, the 0.5%, 2.465V reference and fed into the PROG pin. Amplifier CA2 compares the output the amplifier VA reduce the charge current when battery of CA1 with the programmed current and drives the PWM voltage reaches the preset level. For NiMH and NiCd, VA control loop to force them to be equal. High DC accuracy can be used for overvoltage protection. When the input is achieved with averaging capacitor CPROG. Note that voltage is removed, the VCC pin drops to 0.7V below the IPROG has both AC and DC components. IPROG goes battery voltage, forcing the charger into a low battery drain through R1 and generates a ramp signal that is fed to the (3µA typical) sleep mode. To shut down the charger, PWM control comparator C1 through buffer B1 and level simply pull the VC pin low with a transistor. 1769fa 8
