Datenblatt-Suchmaschine für elektronische Bauteile |
|
ADM8660AN Datenblatt(PDF) 7 Page - Analog Devices |
|
ADM8660AN Datenblatt(HTML) 7 Page - Analog Devices |
7 / 8 page ADM660/ADM8660 REV. A –7– Table II. ADM8660 Charge-Pump Frequency Selection FC OSC Charge Pump C1, C2 GND Open 25 kHz 10 µF V+ Open 120 kHz 2.2 µF GND or V+ Ext Cap See Typical Characteristics GND Ext CLK Ext CLK Frequency/2 INVERTED NEGATIVE OUTPUT +1.5V TO +7V INPUT C1 C2 ADM660 ADM8660 V+ GND OUT LV OSC FC CAP+ CAP– CMOS GATE CLK OSC Figure 21. ADM660/ADM8660 External Oscillator Voltage Doubling Configuration Figure 22 shows the ADM660 configured to generate increased output voltages. As in the inverting mode, only two external ca- pacitors are required. The doubling function is achieved by re- versing some connections to the device. The input voltage is applied to the GND pin and V+ is used as the output. Input voltages from 2.5 V to 7 V are allowable. In this configuration, pins LV, OUT must be connected to GND. The unloaded output voltage in this configuration is 2 (VIN). Output resistance and ripple are similar to the voltage inverting configuration. Note that the ADM8660 cannot be used in the voltage doubling configuration. DOUBLED POSITIVE OUTPUT +2.5V TO +7V INPUT 10µF 10µF ADM660 V+ GND OUT LV OSC FC CAP+ CAP– Figure 22. Voltage Doubler Configuration Shutdown Input The ADM8660 contains a shutdown input that can be used to disable the device and hence reduce the power consumption. A logic high level on the SD input shuts the device down reducing the quiescent current to 0.3 µA. During shutdown the output voltage goes to 0 V. Therefore, ground referenced loads are not powered during this state. When exiting shutdown it takes several cycles (approximately 500 µs) for the charge pump to reach its final value. If the shutdown function is not being used, then SD should be hardwired to GND. Capacitor Selection The optimum capacitor value selection depends the charge- pump frequency. With 25 kHz selected, 10 µF capacitors are recommended, while with 120 kHz selected, 2.2 µF capacitors may be used. Other frequencies allow other capacitor values to be used. For maximum efficiency in all cases, it is recommended that capacitors with low ESR are used for the charge pump. Low ESR capacitors give both the lowest output resistance and lowest ripple voltage. High output resistance degrades the overall power efficiency and causes voltage drops, especially at high Inverting Negative Voltage Generator Figures 19 and 20 show the ADM660/ADM8660 configured to generate a negative output voltage. Input supply voltages from 1.5 V up to 7 V are allowable. For supply voltage less than 3 V, LV must be connected to GND. This bypasses the internal regulator circuitry and gives best performance in low voltage applications. With supply voltages greater than 3 V, LV may be either connected to GND or left open. Leaving it open facili- tates direct substitution for the ICL7660. INVERTED NEGATIVE OUTPUT +1.5V TO +7V INPUT C1 10µF C2 10µF ADM660 V+ GND OUT LV OSC FC CAP+ CAP– Figure 19. ADM660 Voltage Inverter Configuration INVERTED NEGATIVE OUTPUT +1.5V TO +7V INPUT C1 10µF C2 10µF ADM8660 V+ GND OUT LV FC CAP+ CAP– SD SHUTDOWN CONTROL Figure 20. ADM8660 Voltage Inverter Configuration OSCILLATOR FREQUENCY The internal charge-pump frequency may be selected to be either 25 kHz or 120 kHz using the Frequency Control (FC) input. With FC unconnected (ADM660) or connected to GND (ADM8660), the internal charge pump runs at 25 kHz while, if FC is connected to V+, the frequency is increased by a factor of five. Increasing the frequency allows smaller capacitors to be used for equivalent performance or, if the capacitor size is un- changed, it results in lower output impedance and ripple. If a charge-pump frequency other than the two fixed values is desired, this is made possible by the OSC input, which can ei- ther have a capacitor connected to it or be overdriven by an external clock. Please refer to the Typical Performance Charac- teristics, which shows the variation in charge-pump frequency versus capacitor size. The charge-pump frequency is one-half the oscillator frequency applied to the OSC pin. If an external clock is used to overdrive the oscillator, its levels should swing to within 100 mV of V+ and GND. A CMOS driver is, therefore, suitable. When OSC is overdriven, FC has no effect but LV must be grounded. Note that overdriving is permitted only in the voltage inverter configuration. Table I. ADM660 Charge-Pump Frequency Selection FC OSC Charge Pump C1, C2 Open Open 25 kHz 10 µF V+ Open 120 kHz 2.2 µF Open or V+ Ext Cap See Typical Characteristics Open Ext CLK Ext CLK Frequency/2 |
Ähnliche Teilenummer - ADM8660AN |
|
Ähnliche Beschreibung - ADM8660AN |
|
|
Link URL |
Privatsphäre und Datenschutz |
ALLDATASHEETDE.COM |
War ALLDATASHEET hilfreich? [ DONATE ] |
Über Alldatasheet | Werbung | Kontakt | Privatsphäre und Datenschutz | Linktausch | Hersteller 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 |