Electronic Components Datasheet Search |
|
MAX1913 Datasheet(PDF) 4 Page - Maxim Integrated Products |
|
MAX1913 Datasheet(HTML) 4 Page - Maxim Integrated Products |
4 / 11 page 60mA 1.5x High-Efficiency White LED Charge Pumps 4 _______________________________________________________________________________________ Detailed Description The MAX1912/MAX1913 are complete charge-pump boost converters requiring only four small ceramic capacitors. They employ a 750kHz fixed-frequency 50% duty-cycle clock. The MAX1912/MAX1913 use a 1.5x charge- pump mode. This operation has two phas- es (see Figure 1), charge and transfer. In charge phase, transfer capacitors C1 and C2 charge in series from the input voltage. In transfer phase, C1 and C2 are configured in parallel and connected from OUT to IN, transferring charge to COUT. If this system were allowed to operate unregulated and unloaded, it would generate an output voltage 1.5 times the input voltage. Output Regulation The output voltage is regulated by controlling the rate at which the transfer capacitors are charged. The switching frequency and duty cycle are constant, so the output noise spectrum is predictable. Input and out- put ripple are much smaller in value than with other regulating charge-pump topologies because the charge transferred per cycle is only the amount required to supply the output load. Soft-Start The MAX1912/MAX1913 include soft-start circuitry to limit inrush current at turn-on. When starting up with the output voltage at zero, the output capacitor is charged through a ramped current source, directly from the input with no charge-pump action until the output volt- age is near the input voltage. If the output is shorted to ground, the part remains in this mode without damage until the short is removed. Once the output capacitor is charged to the input volt- age, the charge-pumping action begins. Startup surge current is minimized by ramping up charge on the transfer capacitors. As soon as regulation is reached, soft-start ends and the part operates normally. If the SET voltage reaches regulation within 2048 clock cycles (typically 2.7ms), the part begins to run in nor- mal mode. If the SET voltage is not reached by 2048 cycles, the soft-start sequence is repeated. The devices will continue to repeat the soft-start sequence until the SET voltage reaches the regulation point. Shutdown Mode When driven low, SHDN turns off the charge pump. This reduces the quiescent current to approximately 0.1µA. The output is high impedance in shutdown. Drive SHDN high or connect to IN for normal operation. Thermal Shutdown The MAX1912/MAX1913 shut down when their die tem- perature reaches +160°C. Normal operation continues after the die cools by 15°C. This prevents damage if an excessive load is applied or the output is shorted to ground. Design Procedure Setting Output Current (MAX1912) The MAX1912 has a SET voltage threshold of 0.2V, used for LED current regulation (Figure 2). The current through the resistor and LED is: ILED = 0.2/R If additional matching LEDs with ballast resistors are connected to the output as in Figure 2, the current Pin Description PIN NAME FUNCTION 1 GND Ground 2 IN1 Supply Voltage Input. Connect to IN2. Bypass to GND with a 2.2µF ceramic capacitor. 3 C2- Transfer Capacitor 2 Connection, Negative Side 4 C1+ Transfer Capacitor 1 Connection, Positive Side 5 OUT Output. Bypass to GND with a 2.2µF ceramic capacitor. 6 SHDN Shutdown Input. Drive low to turn off the device and disconnect the load from the input. OUT is high impedance in shutdown. Drive high or connect to IN for normal operation. 7 C2+ Transfer Capacitor 2 Connection, Positive Side 8 IN2 Supply Voltage Input. Connect to IN1. 9 C1- Transfer Capacitor 1 Connection, Negative Side 10 SET SET programs the output voltage with a resistive-divider from OUT (MAX1913), or programs output current with a resistor from SET to GND (MAX1912). For the MAX1913, when SET is connected to IN, VOUT is internally set to 5V. |
Similar Part No. - MAX1913 |
|
Similar Description - MAX1913 |
|
|
Link URL |
Privacy Policy |
ALLDATASHEET.COM |
Does ALLDATASHEET help your business so far? [ DONATE ] |
About Alldatasheet | Advertisement | Datasheet Upload | Contact us | Privacy Policy | Link Exchange | Manufacturer List All Rights Reserved©Alldatasheet.com |
Russian : Alldatasheetru.com | Korean : Alldatasheet.co.kr | Spanish : Alldatasheet.es | French : Alldatasheet.fr | Italian : Alldatasheetit.com Portuguese : Alldatasheetpt.com | Polish : Alldatasheet.pl | Vietnamese : Alldatasheet.vn Indian : Alldatasheet.in | Mexican : Alldatasheet.com.mx | British : Alldatasheet.co.uk | New Zealand : Alldatasheet.co.nz |
Family Site : ic2ic.com |
icmetro.com |