|
Details, datasheet, quote on part number:HT7470
| |
Datasheet text preview:
HT7470 Fast Battery Charger
Features
· · · · · · ·
Fast charge NiCd battery High resolution -V detector to determine peak charging voltage Auto cutoff for defective battery Fast charge from C/2 to 4C rate C/10 trickle charge rate Adjustable thermo protection Built-in safety timer
· · · · · ·
Direct drive LED display and alarm buzzer Automatic switching from fast to trickle charge Warm up option for battery Maximum voltage protection Auto-start function 12-bit A/D converter
General Description
The HT7470 is a 4-bit single-chip microcomputer specially designed for NiCd battery fast charge/discharge control. The advanced unique design and multiple protection features of the HT7470 eliminate excessive external components in application circuits, and ensure battery safety and high performance.
Pin Assignment
Block Diagram
Pin Description
Pin No.
1 2 3 4 5 6 7 8
Pin Name
EOC TC L E D1 VD D OSC O OSC I VSS RST
I/O
I I O -- O I -- I
Description
End of A/D conversion. The A/D conversion process takes place during the high period on this pin. When this pin falls low, this indicates the end of the A/D conversion. Over temperature input, active low. LED 1 indicates the charge, discharge and battery status. Positive voltage supply. (5V) OSCI and OSCO are connected to a resistor to generate the system clock. The frequency of the system clock is 1MHz. Negative power supply. Input to reset internal LSI, active low.
1
25th Aug '94
H T 7 47 0
Pin No.
9 10 11 12 13 14 15 16
Pin Name
S0/B Z S 1 /B Z DC HI WARM L E D2 DC H O CHGO SC
I/O
Description
I/O S0, S1 are charge rate inputs. I/O BZ, BZ are a buzzer driving pair. I I O O O O Discharge input, active low. Discharge before charging, active low. Warm-up key, active low. Used only to warm up the battery. LED2 indicates the charge, discharge and battery status. Discharge control output, active high. Charge control output, active high. A/D converter start conversion control output, active low.
Absolute Maximum Ratings
Supply Voltage ...... 0.3V to 5.5V Input Voltage........ VSS0.3V to VDD+0.3V Storage Temperature ....... 50°C to 125°C Operating Temperature ..... 20°C to 70°C
Electrical Characteristics
Symbol
VDD IDD VIL VIH IOL IOH IOL1 IOH1
Parameter
Operating voltage Operating current Input low voltage Input high voltage LED1, LED2 output sink curre nt LED1 output source current CHGO, DCHO, BZ, BZ, SC output sink current CHGO, DCHO, BZ, BZ, SC, LED2 output source current Pull-high resistance System clock -- 5V 5V 5V 5V 5V 5V 5V
Test condition VDD Condition
-- No load fSYS=1MHz -- -- VOL=0.5V VOH=4.5V VOL=0.5V VOH=4.5V S0, S1, WARM DCHI, RST, EOC, TC ROSC=18K
Min.
3.5 -- VSS 0.8VDD 2.5 2.5 2.5 1.5
Typ.
5 1.5 -- -- -- -- -- --
Max.
5.5 3 0.2VDD VDD -- -- -- --
Unit
V mA V V mA mA mA mA K MHz
RPH fSYS
5V 5V
-- --
50 1
-- --
2
25th Aug '94
H T 7 47 0
Fundamental Function
Charge Function Warm-up Function
The charge function of the HT7470 consists of two periods, the charging period and the status detection period. During the charging period, current is supplied to the battery for charging, while during the status detection period, the battery voltage and temperature are measured to determine if the battery is fully charged, open, shorted or damaged.
Trickle Function (C/10)
The HT7470 provides a battery warm-up function to warm up the battery and improve battery efficiency. The warm-up key is enabled only in the warm-up waiting period. A low 20ms pulse in the warm-up waiting period will force the HT7470 to warm-up the battery. During this time the discharge input will be inhibited. The warm-up function is identical to the charge fun ctio n. T he warm-up interval is dependent on the charge rate inputs and is described below:
When the battery has been detected to have reached full charge by the HT7470, the charge rate will switch to trickle charge automatically. The trickle charge function is dependent upon the charge inputs and is shown below. The trickle charge function is different but the trickle charge rate is identical to C/10. This f u n c t i o n is accomplished by adjusting the charge duty cycle which is also implemented in the HT7470. The charge rate KC, is calculated by the following equation: K= Charge current Battery capacity
Charge rate inputs
S1,S0 Charge Count Time (min)
4C
11 150 3.5
2C
10 300 7
1C
01 600 14
C/2
00 1200 28
During battery warm-up, full charge detection and abnormal charge detection are always enabled.
Full Charge Detection
C = Battery capacity
Discharge Function
The HT7470 provides a discharge function to prevent battery memory effect from occuring. If battery memory effect has occured this function will eliminate the effect gradually. The discharge input can be selected to discharge the b a t t e r y before the charge procedure has started. When the battery is empty the HT7470 will start the charge procedure automatically.
There are four full charge detection methods implemented in the HT7470 as described below:
· ·
-V detection Over Temperature: The TC input pin is logical low
Trickle Function (C/10)
3
25th Aug '94
|
|
