Electronic Components Datasheet Search |
|
CLM7660 Datasheet(PDF) 3 Page - Calogic, LLC |
|
CLM7660 Datasheet(HTML) 3 Page - Calogic, LLC |
3 / 8 page CLM7660 CORPORATION CIRCUIT DESCRIPTION The CLM7660 is an excellent voltage doubler, the device has all the characteristic with the exception of two inexpensive 10 µF polarized electrolytic external capacitors. Figure 3 demonstrates the most effective means of using the device as a voltage doubler. Capacitor C1 is charged to a voltage, V+, for the half cycle when switches S1 and S3 are closed. (Note Switches S2 and S4 are open during this half cycle.) During the second half of the operation, switches S2 and S4 are closed, with S1 and S3 open, thereby shifting capacitor C1 negatively by V+ volts. Charge is then transferred from C1 to C2, such that voltage on C2 is exactly V+, asumming ideal switches and no load on C2. The four switches in Figure 3 are MOS power switches, S1 is a P-Channel device, S2, S3 and S4 are N-Channel devices. The major challenge with this approach while integrating the switches, the substrates of S3 and S4 must always remain reversed-biased with respect to their sources, but not so much as to degrade their ON-resistances. In addition, at circuit start-up, and under short circuit conditions (VOUT=V +), the output voltage must be sensed and the substrate bias adjusted accordingly. Failure to accomplish this will result in high power losses and probable device latch-up. The above problem is eliminated in the CLM7660 by a logic network which senses the output voltage (VOUT) together with the level translators, and switches the substrates of S3 and S4 to the correct level to maintain necessary reverse bias. The voltage regulator portion of the CLM7660 is an integral part of the anti-latch-up circuitry. Its inherent voltage drop can degrade operation at low voltages. To improve low-voltage operation, the LV pin should be connected to GND, disabling the regulator. For supply voltages greater than 3.5V, the LV terminal must be left open to ensure latch-up proof operation and prevent device damage. THEORETICAL POWER EFFICIENCY CONSIDERATIONS In theory, a voltage multiplier can approach 100% efficiency if certain conditions are met: 1. The drive circuitry consumes minimal power. 2. The output switches have extremely low ON-resistance and virtually no offset. 3. The impedances of the pump and reservoir capacitors are negligible at the pump frequency. When larger values of C1 and C2 are used, the CLM7660 approaches the above conditions for negative voltage multiplication. Energy is lost only if the transfer of the charge between capacitors if a change in voltage occurs. The energy lost is defined by: E=1/2C1 (V12-V22) During the pump and transfer cycles V1 and V2 are the voltages on C1. If the impedances of C1 and C2 are high at the pump frequency (see Figure 3), compared to the value of RL, there will be a substantial difference in voltages V1 and V2. The most optimum selection would be to make C2 as large as possible to eliminate output voltage ripple, and to utilize a large value for C1 to achieve maximum efficiency of operation. OPERATIONAL RULES: Never exceed maximum supply voltages. Never connect LV terminal to GND for supply voltages over 3.5V. Never short circuit the output to V + supply voltages above 5.5V for extended periods; however, transient conditions including start-up are acceptable. For polarized capacitors, the + terminal of C1 must be connected to pin 2 of the CLM7660 and the + terminal to of C2 must be connected to GND. For high-voltage, elevated temperature applications add a diode DX (reference Figure 1). The 1N914 diode is an appropriate choice. CALOGIC CORPORATION, 237 Whitney Place, Fremont, California 94539, Telephone: 510-656-2900, FAX: 510-651-3025 |
Similar Part No. - CLM7660 |
|
Similar Description - CLM7660 |
|
|
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 |