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PDF SC804A Data sheet ( Hoja de datos )
| Número de pieza | SC804A | |
| Descripción | Fully Integrated 4.4V Lithium-Ion Battery Charger System | |
| Fabricantes | Semtech | |
| Logotipo |  |
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SC804A
Fully Integrated 4.4V Lithium-Ion
Battery Charger Systwewmw.DawtaSihtehet4UT.ciomm er
POWER MANAGEMENT
PRELIMINARY
Description
Features
The SC804A is a fully integrated full-feature, single cell
constant-current/constant-voltage (CC/CV) 4.4V Lithium-
Ion battery charger. With an integrated timer and
complete charge control algorithm, the SC804A is ideal for
stand-alone charger applications. The SC804A contains
programmable pre-charge, fast-charge and termination
current settings. The SC804A can be programmed to
terminate charging based on the output current or the
time-out of the programmable timer. The fast charge
current is typically set with an external resistor, but it can
also be adjusted by applying an analog voltage to the AFC
pin. This feature allows use of a microcontroller to set
charging current via a DAC output.
The SC804A’s 14V input voltage range eliminates the
need for additional protection circuitry required by other
5V chargers to protect against faulty adapters. The
SC804A also incorporates an under-voltage lockout falling
threshold of 3V so that charging will continue if the input
supply goes into a current-limited mode.
Fully integrated charger with FET pass transistor,
reverse-blocking diode, sense resistor, timer, and
thermal protection
Battery voltage controlled to 1% accuracy
Programmable precharge, fastcharge & termination
current over wide range, with analog current control
reference input for design flexibility
Up to 1.5A continuous charge current
Input voltage range from 3V to 14V
Soft-start reduces start-of-charge adapter
load transients
NTC thermistor sense input and adjustable cold
temperature threshold
Adjustable 2 - 6 hour programmable charge timer
0.1μA battery drain current in shutdown and monitor
modes
Small 4mm x 4mm 16 lead MLPQ package
Over-current protection in all modes
Reference ground and battery sense inputs are provided
to eliminate voltage drops during charging due to high
charging currents.
The output voltage to the battery is controlled to within
1% of the programmed voltage. The SC804A can also
Tfuynpcitcioanl Aasppaligceanteiroanl pCuirrpcousiet current source or as a
current source for charging nickel-cadmium (NiCd) and
nickel-metal-hydride (NiMH) batteries.
Typical Application Circuit
Over-voltage protection
Remote Kelvin sensing at the battery terminals
Status indicators for charger-present, charger-active,
over-voltage fault, and error notification
Applications
Cellular phones
PDAs
Handheld meters
Charging stations
Handheld computers
Digital cameras
Programmable current
source
Charger VIN
C1
2.2 μF
R3
RT
NTC
OV_FLT
R1 R2
ERROR
14
13
3
7
4
8
6
5
VCC
OVPB
IPRGM
NTC
ITERM
FLTB
GND
RGND
CPB
CHRGB
RTIM
CTO
BSEN
VOUT
VOUT
AFC
11
10
12
2
1
16
15
9
SC804A
Battery
DAC ISET
Red Green
C2
2.2μF
R4
R5 R6
July 18, 2007
1 www.semtech.com
1 page  
POWER MANAGEMENT
Electrical Characteristics (Cont.)
Parameter
Symbol
Conditions
Pre-Charge Fault
Time-out
Complete Charge
Time-out
TPreQF
TQCOMP
RRTIM = 37.4kΩ
RTIM pulled to VCC
RRTIM = 37.4kΩ
RTIM pulled to VCC
CHRGB On
VCHRGB
Load = 5mA
CHRGB Off
ICHRGB
Leakage Current, V = 5V
CPB On
VCPB
Load = 5mA
CPB Off
ICPB Leakage Current, V = 5V
OVPB On
VOVPB
Load = 5mA
OVPB Off
IOVPB
Leakage Current, V = 5V
FLTB On
VFLTB
Load = 5mA
FLTB Off
IFLTB Leakage Current, V = 5V
Notes:
1) VCC_OP Max is the “Maximum Vsupply” as defined in EIA/JEDEC Standard No. 78, paragraph 2.11.
2) The absolute voltage on CTO must not exceed 6.0V to ensure normal operation.
3) The threshold error is tested at VCTO min and max only.
SC804A
www.DPatRaSEheLeItM4U.IcNomARY
DRAFT
Min Typ Max Units
-20%
-35%
51
44
+20%
+35%
min
-20% 3.37 +20%
-35% 2.89 +35%
hr
0.5 1
V
1 μA
0.5 1
V
1 μA
0.5 1
V
1 μA
0.5 1
V
1 μA
© 2005 Semtech Corp.
5
www.semtech.com
5 Page 
SC804A
POWER MANAGEMENT
Applications Information (Cont.)
The choice of RCT1 and RCT2 is somewhat arbitrary. The
simplest approach is to pick one and compute the other.
A good choice here is RCT1 = 115kΩ, and RCT2 = 221kΩ, as
these standard 1% tolerance values produce the closest
match to the desired voltage divider ratio. With these
resistor nominal values,
VCTO
=
VCC
RCT1
×
+
RCT2
RCT2
= 0.6577 × VCC
which is, nominally, only 0.2% below the target value of
105.6μ5A9t1o×aVV5CCV.
The CTO
charging
network
adapter.
will present a
The nominal
load of only
impedance
presented to the CTO pin is RCT1 || RCT2 = 75.6kΩ. Any
impedance on the order of 100kΩ (or less) is acceptable.
www.DPatRaSEheLeItM4U.IcNomARY
internal voltage references as VOUT pulls VCC DdoRwAnFtTo
near, or below, VCV, creating a reduced output regulation
voltage approximately 200mV below VCC. Thus VCC
cannot be pulled down below VOUT + 200mV. The dropout
voltage will be larger than 200mV whenever the minimum
path resistance multiplied by the output current exceeds
200mV, but it cannot be smaller than 200mV.
This greatest-of-two-limit dropout voltage behavior is
evident in the dropout voltage typical performance plot.
When operating in Adjust Mode (next section), the
regulated minimum dropout voltage depends on the
programmed VOUT regulation voltage, and dropout also
varies with the actual output voltage during CC charging.
See Figure 4 for an illustration of dropout voltage data.
Remote Kelvin Sensing at the Battery
The BSEN pin provides the positive Kelvin sensing voltage
feedback to the CV amplifier and should be connected as
close to the battery + terminal as possible. Likewise, the
RGND pin should be connected directly to the negative
terminal of the battery. This allows the designer great
flexibility in PCB layout and achieves greater accuracy
by sensing the battery voltage directly at the battery
terminals. When laying out the PCB, the designer should
route the BSEN and RGND trace directly to the battery
connection terminals, rather than just to the VOUT and
GND pins on the device.
Dropout Voltage
Dropout voltage is the smallest achievable difference
voltage between VCC and VOUT under a particular
operating condition. Dropout voltage is encountered
during CC charging whenever the current limit of the
charging adapter is less than the SC804A FCI programmed
current. In this case, the adapter voltage (the SC804A
input voltage) will be pulled down to the battery voltage
(the SC804A output voltage) plus the dropout voltage.
Dropout voltage is the larger of two values: (1) the I-R
component, which is the output current multiplied by the
minimum VCC-to-VOUT path resistance (which is highly
temperature dependent), and (2) a regulated minimum
difference voltage, which is output voltage dependent
but is independent of the output current. The regulated
minimum dropout voltage results from the collapse of
Adjust Mode
The SC804A can be configured for an output voltage
other than VCV using Adjust (ADJ) Mode. In Adjust Mode
the output voltage is determined by an external resistor
divider from VOUT to BSEN. When BSEN is connected in
this fashion, VVOUT (during Constant Voltage (CV) charging)
will be controlled such that the voltage at the BSEN pin
(VBSEN) is the reference voltage VBSEN-ADJ.
The output voltage can be set to any voltage desired by
an appropriate choice of divider network resistors, within
the following limits. When the SC804A is programmed for
adjust mode, VVOUT is required to be 150mV less than VVCC,
and VVOUT is required to be 400mV greater than VBSEN.
VVOUT within 150mV of VBSEN guarantees normal mode
operation. This implies that, for BSEN used as a Kelvin
sense of battery voltage, the product of the fast charge
current and the charge path resistance from VOUT to the
Kelvin sense point should not exceed 150mV to ensure
normal mode operation.
The SC804A Adjust Mode schematic is shown in Figures
3a and 3b. Referring to these schematics, the equation
for setting the output voltage is:
( )VOUT = VBSEN-ADJ_TYP x
1+
R11
R12
The capacitor C3 across R8 in the feedback network
introduces zero-pole frequency compensation for stability.
Place the zero according to the following equation to
ensure stability:
R11 × C3 = 2
1
× 100kHz
© 2005 Semtech Corp.
11
www.semtech.com
11 Page | ||
| Páginas | Total 21 Páginas | |
| PDF Descargar | [ Datasheet SC804A.PDF ] | |
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