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參數(shù)資料
| 型號： | ADP3802 |
| 廠商： | Analog Devices, Inc. |
| 元件分類： | 基準(zhǔn)電壓源/電流源 |
| 英文描述： | High Frequency Switch Mode Dual Li-Ion Battery Chargers(高頻開關(guān)模式雙鋰離子充電器) |
| 中文描述： | 高頻開關(guān)雙鋰離子電池充電器（高頻開關(guān)模式雙鋰離子充電器） |
| 文件頁數(shù)： | 11/20頁 |
| 文件大?。?/td> | 278K |
| 代理商： | ADP3802 |
ADP3801/ADP3802
–11–
REV. 0
ADP3800
COMP
EOC
(a)
EOC
Output Terminates Charge
270
V
2N3906
ADP3800
EOC
VL
100k
V
0.1
m
F
(b)
EOC
Turns on LED to Signal Charge Completion
2N3904
3
2
ADP3800
EOC
VL
COMP
100k
V
100k
V
2N3906
0.1
m
F
10k
V
20k
V
20k
V
270
V
(c)
EOC
Terminates Charge and Turns on LED
100k
V
ADP3800
EOC
*LEVEL SHIFTED TO
TO DRIVE PMOS
VL
100k
V
100k
V
2N3906
1
m
F
COMP
RESET
J
K
Q
Q
74H73A
BATSELB*
A/B + BATSELA*
100k
V
0.1
m
F
20k
V
2N3904
3
2
10k
V
(d) Flip-Flop Switches Between Batteries on
EOC
Signal
Figure 23.
EOC
Output Circuits
COMP Node
Both the current loop and the voltage loop share a common,
high impedance compensation node, labeled COMP. A series
capacitor and resistor on this node help to compensate both
loops. The resistor is included to provide a zero in the loop
response and boost phase margin.
The voltage at the COMP node determines the duty cycle of the
PWM. The threshold levels are typically 1.0 V for 0% duty cycle
and 2.0 V for 100% duty cycle, resulting in a total range of
1.0 V. When the ADP3801/ADP3802 first turns on, the COMP
capacitor is at 0.0 V. It has to charge up to at least 1.0 V before
the duty cycle rises above 0% and the pass transistor turns on.
This “soft-start” behavior is desirable to avoid undue stress on
the external components. In addition, whenever the part is
placed in Shutdown or in UVLO, the COMP capacitor is dis-
charged to ensure soft start upon recovery.
The current available to charge and discharge the COMP ca-
pacitor during normal operation is 100
μ
A. Thus, the slew rate
at this node is equal to 100
μ
A divided by the capacitor. For a
typical capacitance of 1
μ
F, the slew rate is 0.1 V/ms. Thus, it
takes about 10 ms before the ADP3801/ADP3802 starts to
operate from a soft-start state. This is regardless of the internal
oscillator frequency. One important note is that the COMP
node is a high impedance point. Any external resistance or leak-
age current on this node will cause an error in both the charge
current control and the final battery voltage.
Gate Drive
The ADP3801/ADP3802 gate drive is designed to provide high
transient currents to drive the pass transistor. The rise and fall
times are typically 20 ns and 200 ns respectively when driving
a 1 nF load, which is typical for a PMOSFET with R
DS(ON)
=
60 m
. Figure 15 shows the typical transient response of the
output stage driving this load from a 10 V supply.
A voltage clamp is added to limit the pull-down voltage to 7 V
below VCC. For example, if VCC is 10 V then the output will
pull down to 3 V minimum, limiting the V
GS
voltage applied to
the external FET.
Low Dropout Regulator and Reference
A 3.3 V LDO is used to generate a regulated supply for internal
circuitry. Additionally, the LDO can deliver up to 10 mA of
current to power external circuitry such as a microcontroller. A
1.0
μ
F capacitor must be placed close to the VL pin to ensure
stability of the regulator. Due to the design of the regulator,
stability is not contingent on the ESR for the output capacitor.
Many different types of capacitors can be used providing flex-
ibility and ease of design. The LDO also includes a high accu-
racy, low drift internal reference equal to half of VL to set levels
within the part. During shutdown and UVLO, both the refer-
ence and the LDO remain active.
Shutdown
The IC may be placed in shutdown at any time to stop charging
of the batteries and to conserve power. For example, to safely
switch from one battery to the next, the part should be shut
down to momentarily interrupt charging. Also, if the batteries
have completed charging or no batteries are present, then the
part may be placed in shutdown to save power. A logic low on
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相關(guān)代理商/技術(shù)參數(shù) |
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| ADP3802AR | 制造商:AD 制造商全稱:Analog Devices 功能描述:High Frequency Switch Mode Dual Li-Ion Battery Chargers |
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