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PDF LM3655 Data sheet ( Hoja de datos )
| Número de pieza | LM3655 | |
| Descripción | Charge Control and Protection IC for embedded single | |
| Fabricantes | National Semiconductor | |
| Logotipo |  |
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November 2004
www.DataSheet4U.com
LM3655
Charge Control and Protection IC for embedded single
cell Li-Ion/Polymer batteries
1.0 General Description
The LM3655 provides complete charge control, discharge
control and battery safety of a single Lithium-Ion cell. It
supports battery charging by using a variety of power supply
types including unregulated current-limited wall adapters,
regulated wall adapters and vehicle power adapters. Charge
current control is achieved using an external bipolar PNP
power transistor.
Furthermore, the LM3655 provides effective and compre-
hensive discharge control functionality. All operating load
current is supplied by the Li-Ion battery and passes through
this IC. This allows the battery power to disconnect due to
overload, short-circuit or low battery conditions. The IC also
offers extensive battery safety protection against over-
voltage and over-current. The internal safety circuit is
backed up by an identical circuit to provide safety redun-
dancy. The LM3655 requires minimal external components
and is packaged in a micro surface mount device for inte-
gration in a single cell battery pack.
2.0 Key Specifications
n 1% precision pin-selectable nominal 4.10V and 4.16V
termination voltages
n Up to 1.2A full-rate charge current
n Safety Shunt voltage 4.35V
n 800 mW power regulation of external PNP at 25˚C
allows operation up to 30V (peak-to-peak) and 18V DC
3.0 Features
n Input over-voltage protection for load and battery pack
n Input over-current protection for load and battery pack
n Reverse current protection
n Reverse charger protection
n Input short circuit protection that protects the cell from a
short on the charger-connector
n Output overload current and short circuit protection
n Complete charge control with pre-charging for depleted
batteries, full-rate and trickle charging.
n Support for charging with regulated and non-regulated
wall adapters and vehicle power adapters.
n Power regulation of the external Power PNP
n Chemistry selection for Li-ion and Li-polymer
n Complete linear Peak detector function for filtering ripple
on input power supply
n Digital filtering of the cell voltage transients during
transmit pulses when LM3655 is used in a battery pack
for cell phones.
n 25-pin, 2.5 mm x 2.5 mm microSMD package for
mounting on four layered PCB inside the battery pack.
4.0 Applications
n Cell phones and other portable applications which use
embedded Li-ion batteries
5.0 Typical Application Circuit
20111501
Because the LM3655 and associated external components provide safety protection for both the Li-Ion cell and the phone circuitry, appropriate precautions
must be taken in system design and layout to ensure proper operation.
© 2004 National Semiconductor Corporation DS201115
www.national.com
1 page  
10.0 Pin Functions (Continued)
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10.4 VDETECT
This pin is coupled to the external power supply through a series resistance (R4). It is used to determine when an external source
(charger) is connected, which in turn initiates the device’s charge control logic. The CHRG_DETB output is set based on input to
this pin.
10.5 DISABLE
The phone can stop the charge current through use of the DISABLE logic input pin of the IC. Asserting a logic high on the
DISABLE Pin of the IC will force the control pin (CNTRL) to turn off the external Drive (Q2) and Pass (Q1) transistors so there
is no charge current to the cell. The DISABLE input can be driven high by the phone’s logic at any time to interrupt the charge
current. Use of the DISABLE pin during charging can allow the phone to measure the cell’s true voltage by peripheral circuitry
(without the presence of charge current input) if desired.
Additionally, a high-to-low transition on the DISABLE pin (thus re-enabling the charger operation), will reset the charge control
state machine.
10.6 CHEMISTRY
The CHEMISTRY pin provides a logic input to the IC that determines the termination threshold for Li-ion cell charging. A logic low
applied to this pin selects the lower charging threshold or termination voltage (VTERML), a logic high selects the higher charging
threshold (VTERMH).
Because different cell types may require slightly different charge termination thresholds, the LM3655 supports a pin-
programmable selection between two different settings. The lower threshold is nominally 4.10V, and the higher threshold is
nominally 4.16V.
10.7 HIB_EN
This pin provides a logic input to the IC that when held high during a debounce period of 32 mS, M4 will be latched open even
if the cell voltage is above VCHARGE_LOW. This pin has a 10K pull-down resistor internal to the IC so that the IC will default on.
10.8 HIS_DIS
This pin provides a logic input to the IC that when held low momentarily, the latch holding M4 open is cleared allowing it to be
closed when the cell voltage is above VCHARGE_LOW. This pin has a 100K pullup resistor to the CELL pin internal to the IC.
10.9 BATT_DETB
BATT_DETB indicates to the LM3655 IC that a cell is present in the system. This pin provides a logic input to the IC that when
held low, the IC will be able to detect the presence of a charger. There is a 100K pull-up resistor internal to the IC on this pin, which
is supplied from the charger (not from the cell).
A series 10K resistor is to be used between this pin and the removable battery to protect the IC against ESD.
10.10 CHRG_STATE
CHRG_STATE is an open-drain logic output to the phone, and can be used to provide a simple battery-metering indication during
charge mode. During charge mode, with current flowing into the cell, the Li-ion cell voltage cannot be used for an accurate
indication of state of charge. If a battery is at a relatively low state of charge, it will remain in the “full-rate” charge mode for some
period of time when connected to the external power supply. When the cell reaches a higher state of charge, the charge control
switches to the trickle/top-off mode. Thus, this signal is logic low during full-rate charge mode and high during the trickle/top-off
mode. The exact percentage of “full” at this crossover point will vary depending on many conditions, primarily full-rate charge
current level, but is expected to be >60% for typical use with a mid-rate charger.
This information can be used to provide a simple “charging” or “ready” indication by the system for the battery status meter during
charge. If combined with a timer, or other means of interaction by the system (such as periodic control of the DISABLE pin
combined with cell voltage measurements during periods of no current flow) a more complete metering method may be
implemented if desired.
10.11 CHRG_DET
This is an open-drain output to the phone’s power management IC that indicates the connection of an external power supply.
Typical application uses a 30K pull-up resistor to RADIO_B+. When a charger is detected, this output is pulled LOW by the
internal logic of the LM3655. This signal may be pulled up to a low-voltage logic rail such as 2.75V or 1.8V regulated voltage. It
is assumed that the voltage used to pull-up is no higher than the cell voltage.
10.12 CNTRL
This is an analog output to control Q2, the NPN drive transistor. The CNTRL output is adjusted to deliver the appropriate level of
current required by the charge algorithm for full-rate or trickle/top-off charging. During full-rate charging, CNTRL is set such that
Q1 will be saturated. During trickle/top-off mode, CNTRL will be set in order to maintain the appropriate cell clamp voltage (4.10V
or 4.16V as desired). Furthermore, if the power-monitoring circuit determines that excess power is being dissipated in, the CNTRL
signal will be further reduced to limit current flowing through Q1. This ensures that the Q1 pass device remains within safe power
dissipation limits.
5 www.national.com
5 Page 
11.0 Charge Control Functions (Continued)
Unless otherwise noted, the following specifications apply over the Normal Temperature Range.
Specification
Test Conditions
Min
“VTERMX = VTERMH” −20˚C to +70˚C
Q1 Unsaturated Threshold “Q1UNSAT”
@ 25˚C
Chemistry Pin HIGH
3.90
550
Over Normal Temperature Range
550
“VPHONE_ON” at CELL Pin
Maximum Full Rate Current “ICHRG-MAX”
@ 25˚C
Cell voltage at which phone is operational
2.88
1.0
Over Normal Temperature Range
1.0
Maximum Power Dissipation of Pass
Transistor
For R4A + R4B = 2 kΩ
“PPASS_MAX”
@ 25˚C
@ −20˚C
VPS – VCELL = 5V to 22V
530
530
@ +70˚C
475
www.DataSheet4U.com
Typ Max Units
4.25 V
-
-
3.00
795
795
3.12
mW
mW
V
1.2 1.4
1.2 1.4
A
A
650 800 mW
650 880 mW
650 800 mW
11.2.6 Trickle/Top-Off Mode
After the full-rate charge is completed and the cell is charged to VTERMX, the current will be reduced to the trickle charge current.
The pass transistor Q1 will no longer be in saturation and will now operate in linear mode. The maximum trickle current is
ITRICKLE_MAX unless the power dissipation of Q1 exceeds PPASS_MAX. If the power dissipation of Q1 exceeds PPASS_MAX, the
trickle current will be further reduced until the power dissipation of Q1 is less than or equal to PPASS_MAX.
During the transition from full-rate to trickle charge, the voltage of the cell will relax (IR drop due to cell internal impedance), but
the cell will again eventually be charged up again to VTERMX. While the LM3655 allows the trickle current continue to flow to the
cell, it will constantly monitor the cell voltage not to exceed VTERMX. The IC will maintain the cell voltage at VTERMX by gradually
reducing the trickle current, and eventually no charge current will flow into the cell.
The charge rate between VSUV and VCHARGE_LOW is limited to the lowest setting of the Trickle charge range (ITRICKLEMIN). Once
VCHARGE_LOW is reached, the trickle charger will remain charging but can use the full range of trickle charge, from ITRICKLEMIN to
ITRICKLEMAX.
11.2.7 Peak Detector Function
The LM3655 device uses two independent peak detector circuits. One is used for filtering the ripple from the input power supply,
and the other for minimizing the IR drop of the cell voltage during transmit pulses (if the phone is operated while connected to a
charger). The peak detector circuits allow the device to be less sensitive to the ripple-induced noise that could unintentionally
trigger the internal circuit thresholds of the IC.
The peak detector circuit for smoothing the power supply ripple has its input connected across to the emitter of Q1 to CELL for
monitoring Q1 VCE voltage and voltage across M5. The filtered voltage from the peak detector is used by the circuit that regulates
the power of the external PNP pass transistor Q1. The power limiting circuit determines the maximum charge current such that
the maximum power dissipation of Q1 [(Q1 VCE +Ma5)* Ic] is lways at PPASS_MAX.
The peak detector for the cell voltage is used to smooth the sensed values for cell voltage drop during the transmit pulses. The
peak detector is in essence a digital filter with transient response characteristics as outlined below. Two parameters are
associated with the peak detector, decay rate and attack rate. Figure 4 a) and b) below show the decay and attack rates of the
power supply ripples and for the transmit pulses on the cell (output) voltage respectively. The typical input voltage filter decay and
attack rates are respectively 5.0 ms and 15.6 µs. The typical output voltage filter decay and attack rates are respectively 4 mV/ms
and 1.4V/ms.
11 www.national.com
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| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet LM3655.PDF ] | |
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