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74LV4799DB Arkusz danych(PDF) 5 Page - NXP Semiconductors |
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74LV4799DB Arkusz danych(HTML) 5 Page - NXP Semiconductors |
5 / 18 page Philips Semiconductors Product specification 74LV4799 Timer for NiCd and NiMH chargers 1998 Apr 20 5 Self-discharge mode. If DIS is HIGH and PWRS is inactive (LOW or open), the battery is being neither charged nor discharged. The circuit is in the self-discharge mode. This mode represents the battery leakage (self-discharge). The counter counts down. The clock frequency is determined by the external capacitor and resistor at the RS output. When the counter reaches the zero state, it stops. LED mode select. The LED output drives a battery status LED which indicates the charge/full status of the battery. For optimum flexibility, two modes of operation are built-in. • Mode 1: If SEL is LOW, the LED output is active LOW in the charge mode, and the LED blinks with a frequency of about 1 Hz during trickle charge. • Mode 2: If SEL is HIGH or open, the LED output blinks with a frequency of about 0.25 Hz in the charge mode, and is active LOW during trickle charge. In the discharge or self-discharge mode, the LED output is open except when PWRS is active (HIGH or pulsed). Then, the battery is charging and discharging simultaneously. Although the discharge mode is dominant, the LED output is active when PWRS is also active. NOTE: The blink frequency depends on the oscillator frequency. (See application information) Low indication. As part of the user interface, the MOLLI output shows when the battery needs to be charged. MOLLI stands for More Or Less Low Indication (active LOW). The function is as follows: In the discharge mode, (DIS is active LOW), the counter counts down and, when it reaches the zero state, it stops. If DIS is switched HIGH, the MOLLI output gives an output signal of four periods of about one second, with a 50% duty cycle. This can be used to activate a buzzer. The MOLLI output signal of four periods will be interrupted as soon as PWRS is activated. Alarm indication. If an almost completely discharged battery is connected to the charger, it may not be noticed by the user if the load switch is still on. To prevent damaging the battery, an alarm signal on the LED output will alert the user to switch off the load. The alarm signal is easily recognized, because the LED output will blink at a higher frequency than normal (about 5 Hz instead of 1 Hz). This alarm indication is only active if the SEL input is HIGH or open. If the SEL input is LOW, no alarm indication is present, because in many applications simultaneous charging and discharging is quite acceptable. (See charge/discharge mode) Scan test mode. If the SCAN input (pin 14) is made active HIGH, the circuit is in the test mode. The tester clock is connected to the IOSC pin (pin 13). In the scan mode, the on–chip oscillator is bypassed to allow rapid testing of the divider/counter. The scan test patterns are available on request. The scan test data is entered serially through the SCI input (pin 15). The scan out data is present on the MOLLI/SCO output (pin 6), which then acts as a scan output. Remaining energy indication. The scan test facility can be used as a remaining energy indication because the value of the counter can be read out at the scan output (MOLLI/SCO). This is done by briefly interrupting the normal mode of operation, putting the circuit in the scan mode, and reading out the counter value. The circuit then reverts to the normal mode. This only works correctly with the MOLLI/SCO output and SCI input linked (round coupled loop) and with exactly 49 clock pulses applied to the IOSC input. The serial scan-out data is available on the MOLLI/SCO output. The value of the counter can be decoded by reading the correct bits. Details are given later in the section “Application information”. Output drivers EN and EN. In one-cell battery (low-voltage) applications, the drive from the ENABLE output (EN) is insufficient to provide the base current directly for the external bipolar PNP regulator transistor. The inverse signal has therefore been made available at the ENABLE output (EN) to drive an extra bipolar NPN transistor that can provide the base current for the bipolar PNP regulator transistor as shown in Figure 2. FUNCTION TABLE 1 OPERATING INPUTS OUTPUTS DIVIDER/COUNTER OPERATING MODES PWRS VIN DIS EN EN RC RD RS MODE VALUE Charge H or H H H L Z Z Count up 22 sections < max Trickle charge H or H H Z Stop max Charge/discharge H or H L H L Z Z Count down 18 sections ≥ min Discharge L or open X L L Z Z Z Count down 18 sections ≥ min Self-discharge L or open X H L Z Z Z Count down 27 sections ≥ min |
Podobny numer części - 74LV4799DB |
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Podobny opis - 74LV4799DB |
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