Philips Semiconductors
Product specification
Timer for NiCd and NiMH chargers
74LV4799
Self-discharge mode.
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)
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 R output.
When the counter reaches the zero state, it stops.
S
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.
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 I
pin (pin 13). In
OSC
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.
• 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.
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
NOTE: The blink frequency depends on the oscillator frequency.
(See application information)
to the I
input.
Low indication.
OSC
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.
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.
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
FUNCTION TABLE 1
INPUTS
OUTPUTS
DIVIDER/COUNTER
MODE
OPERATING
MODES
PWRS
H or
V
IN
DIS
H
EN
EN
R
R
R
S
VALUE
< max
max
C
D
Charge
H
H
L
Z
Z
Count up 22 sections
Trickle charge
Charge/discharge
Discharge
H
H
X
X
H
Z
Stop
H or
L
H
L
L
L
Z
Z
Z
Z
Z
Count down 18 sections
Count down 18 sections
Count down 27 sections
≥ min
≥ min
≥ min
H or
L or open
L or open
L
Z
Z
Self-discharge
H
Z
5
1998 Apr 20
5秒后页面跳转
SI2301 N沟道MOSFET：资料手册参数分析
ADC0809逐次逼近寄存器型模数转换器：资料手册参数分析
AD9361捷变收发器：全面参数解析与关键特性概览
IRF3205功率MOSFET：资料手册参数分析
微信公众号
抖音公众号
浙公网安备 33010502006866号 浙ICP备10014259号-119
营业执照ICP证
技术参数
数据手册
如果您发现信息不准确，
