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參數(shù)資料
| 型號： | SAA1502ATS |
| 廠商： | NXP SEMICONDUCTORS |
| 元件分類： | 電源管理 |
| 英文描述： | Safety IC for Li-ion |
| 中文描述： | 1-CHANNEL POWER SUPPLY SUPPORT CKT, PDSO16 |
| 封裝： | 5.30 MM, PLASTIC, MO-150AC, SOT-338-1, SSOP-16 |
| 文件頁數(shù)： | 5/20頁 |
| 文件大?。?/td> | 108K |
| 代理商： | SAA1502ATS |
1998 Jan 15
5
Philips Semiconductors
Preliminary specification
Safety IC for Li-ion
SAA1502ATS
A short time is needed to charge the gate of SW1. During
this time the backgate diode between drain and source of
SW1 conducts.
The system will remain in the discharge enable mode
unless:
The battery voltage drops below 3.95 V, which results in
re-entering normal operation. This transition is not
externally noticeable, because both switches remain low
ohmic.
A charger is connected which will immediately
deactivate SW1 if I
ch
> 280 mA. As an additional safety
precaution also V
CC
> 4.18 V yields the same reaction,
because a small current of a charger may be undetected
with the condition of I
ch
> 280 mA, leading to
overcharging the Li-ion cell.
Current protection will deactivate both switches and is
detected by a voltage drop or rise of V
VM
when both
switches are activated. A release of this state can only be
achieved by removing the load (or charger).
The temperature protection overrules all other states and
yields deactivation of both switches. This situation is
activated at a junction temperature of 130
°
C and released
at a junction temperature of 60
°
C. The temperature
protection is followed by a return to its preceding mode.
Normal mode
In case of correct temperature, battery voltage and
(dis)charge current, the system will be in the normal
operation mode. Both the charge and discharge output will
be active high, so both switches are conducting
(SW1 = SW2 = 1).
Discharge inhibit mode
If the battery drops below 2.3 V, the system will switch to
the discharge inhibit mode. In this mode only charging of
the battery is allowed (SW1 = 1, SW2 = 0). The system will
return to the normal operation mode as soon as the battery
voltage will exceed 3.6 V, or by detection of a charge
current.
The overdischarge detection of 2.3 V has a delay of 40 ms
typical. The voltage detection level 3.6 V has a delay of
50 ms typical. Because a charge current is necessary to
increase the battery voltage, the system will normally
switch to the normal operation mode at V
CC
= 2.3 V by
detecting a charge current. But if the charge current is too
small to detect, the 3.6 V detection is a backup.
To prevent an instable situation between the normal
operation and the discharge inhibit mode when the battery
is charged at a voltage below 2.3 V, an extra condition of
V
bat
> 2.3 V is included going from the discharge inhibit to
the normal operation mode.
Power-down mode
At low battery voltage the supply current is reduced to
100 nA for minimizing the discharge of the battery by the
SAA1502ATS.
At the Power-down mode all analog circuitry, except
circuitry for detecting a charger present (V
CC
V
VM
> 3 V),
is disabled. The Power-down mode is entered when the
system is in the discharge inhibit mode and no charger is
present. The discharge inhibit mode will be entered again
as soon as a charger is connected.
The detection of a charger is accomplished by detecting a
voltage difference of 3 V between V
CC
and VM. In this
mode the voltage difference (see Fig.5) is:
V
CC
V
VM
= V
bat
V
R1
+ V
j(DO)
+ V
ds(CO)
≈
V
bat
+ 0.6 V.
So in the application the battery has to be charged in the
Power-down mode until such a voltage that
V
CC
V
VM
= 3 V.
Reset mode
If the battery voltage is below 1.9 V, the system will be in
the reset mode. Because in this mode the charge pump is
disabled and battery charging should be possible, the
charge FET is switched on with a reduced V
gs
voltage.
As soon as the battery voltage exceeds 2.25 V the system
will switch to the discharge inhibit mode and the charge
pump will be activated again.
Zero voltage start-up
The system has to be able to charge the battery at ‘0 Volt’.
This means that when connecting a charger in case of a
complete empty battery, the charge FET has to be active.
In the reset mode the charge FET (SW1) is connected via
a diode to V
CC
, so that the charge FET will be active when
the V
VM
voltage is negative. The discharge inhibit mode
will be entered as soon as a battery voltage exceeds
2.25 V.
Charge inhibit mode
If the battery voltage exceeds 4.18 V, the charge inhibit
mode will be entered. At this mode the battery can only be
discharged (SW1 = 0, SW2 = 1). The overcharge
detection has a delay of 40 ms. This delay can be
increased by an external capacitor. The delay time is then
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