Datasheet LT1505 (Analog Devices) - 7
| Hersteller | Analog Devices |
| Beschreibung | Constant-Current/Voltage High Efficiency Battery Charger |
| Seiten / Seite | 16 / 7 — PIN FUNCTIONS. BAT2 (Pin 20):. SENSE (Pin 21):. SPIN (Pin 22):. PRESET … |
| Dateiformat / Größe | PDF / 170 Kb |
| Dokumentensprache | Englisch |
PIN FUNCTIONS. BAT2 (Pin 20):. SENSE (Pin 21):. SPIN (Pin 22):. PRESET BATTERY VOLTAGE. PIN SELECTION. BAT (Pin 23):. VCC (Pin 24):
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LT1505
U U U PIN FUNCTIONS
the noninverting input to the amplifier, VA in the Block
BAT2 (Pin 20):
This pin is used to connect the battery to Diagram, that controls the charging current when the the internal preset voltage setting resistor. An internal device operates in constant voltage mode. The amplifier switch disconnects the internal divider from the battery VA controls the charging current to maintain the voltage when the device is in shutdown or when power is discon- on the VFB pin at the reference voltage (2.465V). Input bias nected. This disconnect function eliminates the current current for VA is approximately 3nA. The LT1505 incorpo- drain due to the resistor divider. This pin should be rates a resistor divider that can be used to select the connected to the positive node of the battery if the internal correct voltage for either three or four 4.1V or 4.2V preset divider is used. This pin should be grounded if an lithium-ion cells. For three cells the 3CELL pin is shorted external divider is used. Maximum input voltage on this to the VFB pin. For four cells the 3CELL pin is not con- pin is 20V. nected. For 4.1V cells the 4.1V pin is connected to the VFB
SENSE (Pin 21):
This pin is the noninverting input to the pin and the 4.2V pin is not connected. For 4.2V cells the current amplifier CA1 in the Block Diagram. Typical bias 4.2V pin is connected to VFB and the 4.1V pin is not current is – 50µA. connected. See the table below.
SPIN (Pin 22):
This pin is for the internal amplifier CA1
PRESET BATTERY VOLTAGE PIN SELECTION
bias. It must be connected as shown in the application 12.3V (3 × 4.1V Cell) 4.1V, VFB, 3CELL Short Together circuit. 16.4V (4 × 4.1V Cell) 4.1V, VFB, Short Together, 3CELL Floats
BAT (Pin 23):
Current Amplifier CA1 Inverting Input. 12.6V (3 × 4.2V Cell) 4.2V, VFB, 3CELL Short Together Typical bias current is – 50µA. 16.8V (4 × 4.2V Cell) 4.2V, VFB, Short Together, 3CELL Floats
VCC (Pin 24):
Input Supply. For good bypass, a low ESR For battery voltages other than the preset values, an capacitor of 10µF or higher is required. Keep the lead external resistor divider can be used. If an external divider length to a minimum. VCC should be between 11V and 24V. is used then the 4.1V, 4.2V and 3CELL pins should not be Do not force VCC below VBAT by more than 1V with the connected and BAT2 pin should be grounded. To maintain battery present. the tight voltage tolerance, the external resistors should
BOOSTC (Pin 25):
This pin is used to bootstrap and supply have better than 0.25% tolerance. Note that the VFB pin will the current sense amplifier CA1 for very low dropout float high and inhibit switching if it is left open. condition. VCC can be as low as only 0.4V above the battery
VC (Pin 18):
This is the control signal of the inner loop of voltage. A diode and a capacitor are needed to get the the current mode PWM. Switching starts at 0.9V, higher voltage from VBOOST. If low dropout is not needed and VCC VC corresponds to higher charging current in normal is always 3V or higher than VBAT, this pin can be left operation and reaches 1.1V at full charging current. A floating or tied to VCC. Do not force this pin to a voltage capacitor of at least 0.33µF to GND filters out noise and lower than VCC. Typical input current is 1mA. controls the rate of soft start. Pulling this pin low will stop
GBIAS (Pin 26):
This is the output of the internal 9.1V switching. Typical output current is 60µA. regulator to power the drivers and control circuits. This pin
PROG (Pin 19):
This pin is for programming the charge must be bypassed to a ground plane with a minimum of current and for system loop compensation. During normal 2.2µF ceramic capacitor. Switching will stop when VGBIAS operation, VPROG stays at 2.465V. If it is shorted to GND or drops below 7V. more than 1mA is drawn out of the pin, switching will stop.
BGATE (Pin 27):
Low Side Power MOSFET Drive. When a microprocessor controlled DAC is used to pro- gram charging current, it must be capable of sinking
PGND (Pin 28):
MOSFET Driver Power Ground. A solid current at a compliance up to 2.465V. system ground plane is very important. See the LT1505 Demo Manual for further information. 1505fc 7
U U U PIN FUNCTIONS
the noninverting input to the amplifier, VA in the Block
BAT2 (Pin 20):
This pin is used to connect the battery to Diagram, that controls the charging current when the the internal preset voltage setting resistor. An internal device operates in constant voltage mode. The amplifier switch disconnects the internal divider from the battery VA controls the charging current to maintain the voltage when the device is in shutdown or when power is discon- on the VFB pin at the reference voltage (2.465V). Input bias nected. This disconnect function eliminates the current current for VA is approximately 3nA. The LT1505 incorpo- drain due to the resistor divider. This pin should be rates a resistor divider that can be used to select the connected to the positive node of the battery if the internal correct voltage for either three or four 4.1V or 4.2V preset divider is used. This pin should be grounded if an lithium-ion cells. For three cells the 3CELL pin is shorted external divider is used. Maximum input voltage on this to the VFB pin. For four cells the 3CELL pin is not con- pin is 20V. nected. For 4.1V cells the 4.1V pin is connected to the VFB
SENSE (Pin 21):
This pin is the noninverting input to the pin and the 4.2V pin is not connected. For 4.2V cells the current amplifier CA1 in the Block Diagram. Typical bias 4.2V pin is connected to VFB and the 4.1V pin is not current is – 50µA. connected. See the table below.
SPIN (Pin 22):
This pin is for the internal amplifier CA1
PRESET BATTERY VOLTAGE PIN SELECTION
bias. It must be connected as shown in the application 12.3V (3 × 4.1V Cell) 4.1V, VFB, 3CELL Short Together circuit. 16.4V (4 × 4.1V Cell) 4.1V, VFB, Short Together, 3CELL Floats
BAT (Pin 23):
Current Amplifier CA1 Inverting Input. 12.6V (3 × 4.2V Cell) 4.2V, VFB, 3CELL Short Together Typical bias current is – 50µA. 16.8V (4 × 4.2V Cell) 4.2V, VFB, Short Together, 3CELL Floats
VCC (Pin 24):
Input Supply. For good bypass, a low ESR For battery voltages other than the preset values, an capacitor of 10µF or higher is required. Keep the lead external resistor divider can be used. If an external divider length to a minimum. VCC should be between 11V and 24V. is used then the 4.1V, 4.2V and 3CELL pins should not be Do not force VCC below VBAT by more than 1V with the connected and BAT2 pin should be grounded. To maintain battery present. the tight voltage tolerance, the external resistors should
BOOSTC (Pin 25):
This pin is used to bootstrap and supply have better than 0.25% tolerance. Note that the VFB pin will the current sense amplifier CA1 for very low dropout float high and inhibit switching if it is left open. condition. VCC can be as low as only 0.4V above the battery
VC (Pin 18):
This is the control signal of the inner loop of voltage. A diode and a capacitor are needed to get the the current mode PWM. Switching starts at 0.9V, higher voltage from VBOOST. If low dropout is not needed and VCC VC corresponds to higher charging current in normal is always 3V or higher than VBAT, this pin can be left operation and reaches 1.1V at full charging current. A floating or tied to VCC. Do not force this pin to a voltage capacitor of at least 0.33µF to GND filters out noise and lower than VCC. Typical input current is 1mA. controls the rate of soft start. Pulling this pin low will stop
GBIAS (Pin 26):
This is the output of the internal 9.1V switching. Typical output current is 60µA. regulator to power the drivers and control circuits. This pin
PROG (Pin 19):
This pin is for programming the charge must be bypassed to a ground plane with a minimum of current and for system loop compensation. During normal 2.2µF ceramic capacitor. Switching will stop when VGBIAS operation, VPROG stays at 2.465V. If it is shorted to GND or drops below 7V. more than 1mA is drawn out of the pin, switching will stop.
BGATE (Pin 27):
Low Side Power MOSFET Drive. When a microprocessor controlled DAC is used to pro- gram charging current, it must be capable of sinking
PGND (Pin 28):
MOSFET Driver Power Ground. A solid current at a compliance up to 2.465V. system ground plane is very important. See the LT1505 Demo Manual for further information. 1505fc 7