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PDF MAX1612EEE Data sheet ( Hoja de datos )
| Número de pieza | MAX1612EEE | |
| Descripción | Bridge-Battery Backup Controllers for Notebooks | |
| Fabricantes | Maxim Integrated | |
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19-4785; Rev 0; 11/98
EVFAOLLULAOTWIOSNDKAITTAMSAHNEUEATL
Bridge-Battery Backup Controllers
for Notebooks
General Description
The MAX1612/MAX1613 manage the bridge battery
(sometimes called a hot-swap or auxiliary battery) in
portable systems such as notebook computers. They
feature a step-up DC-DC converter that boosts 2-cell or
3-cell bridge-battery voltages up to the same level as
the main battery. This voltage boosting technique
reduces the number of cells otherwise required for a 6-
cell plus diode-OR bridging scheme, reducing overall
size and cost. Another key feature is a trickle-charge
timer that minimizes battery damage caused by con-
stant charging and eliminates trickle-charge current
drain on the main battery once the bridge battery is
topped off.
These devices contain a highly flexible collection of
independent circuit blocks that can be wired together
in an autonomous stand-alone configuration or used in
conjunction with a microcontroller. In addition to the
boost converter and charge timer, there is a micropow-
er linear regulator (useful for RTC/CMOS backup as
well as for powering a microcontroller) and a high-pre-
cision low-battery detection comparator.
The two devices differ only in the preset linear-regulator
output voltage: +5.0V for the MAX1612 and +3.3V for
the MAX1613. Both devices come in a space-saving
16-pin QSOP package.
Applications
Notebook Computers
Portable Equipment
Backup Battery Applications
Features
o Reduce Battery Size and Cost
o Four Key Circuit Blocks
Adjustable Boost DC-DC Converter
NiCd/NiMH Trickle Charger
Always-On Linear Regulator (+28V Input)
Low-Battery Detector
o Low 18µA Quiescent Current
o Selectable Charging/Discharging Rates
o Preset Linear-Regulator Voltage
5V (MAX1612)
3.3V (MAX1613)
o 4V to 28V Main Input Voltage Range
o Internal Switch Boost Converter
o Small 16-Pin QSOP Package
PART
MAX1612EEE
MAX1613EEE
Ordering Information
TEMP. RANGE
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
16 QSOP
16 QSOP
Typical Operating Circuit
Pin Configuration
MAIN BATTERY
OR
WALL
ADAPTER
LRI
DC-DC
OUTPUT
V+
BBATT
AUXILIARY
BRIDGE
BATTERY
MAX1612
MAX1613
APPLICATION
CIRCUIT
MAX1630
DC-DC
CONVERTER
+3.3V
+5V
VCPU
TOP VIEW
ISET 1
BBATT 2
LX 3
LBO 4
BBON 5
DCMD 6
CCMD 7
FULL 8
MAX1612
MAX1613
QSOP
16 LRI
15 LRO
14 PGND
13 CD
12 CC
11 GND
10 LBI
9 FB
________________________________________________________________ Maxim Integrated Products 1
For free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800.
For small orders, phone 1-800-835-8769.
1 page  
Bridge-Battery Backup Controllers
for Notebooks
Pin Description
PIN NAME
FUNCTION
Bridge-Battery Charge-Current Input. Connect a current-setting resistor from this input to a voltage
1
ISET
higher than the bridge battery. Maximum current rating is 10mA. Pulling ISET below 0.4V resets the
internal counter.
2
BBATT
Bridge-Battery Connection. Bridge-battery charger output.
3 LX Step-Up DC-DC Converter N-Channel MOSFET Drain. The maximum operating range is 12V.
4
LBO
Open-Drain Low-Battery Detector Output. When VLBI falls below 1.8V, LBO sinks current. When
VLBI rises above 2.0V, LBO becomes high impedance.
Bridge-Battery On Input. When high, the DC-DC converter turns off. When pulled low through an
5
BBON
external resistor, the resistor sets the peak inductor current. The inductor current is approximately
42,000 times the current in the external resistor (RBBON).
Discharge Command Input. When low with CCMD high, the internal timer counts down at a
6
DCMD
frequency set by the CD capacitor. When both DCMD and CCMD are low, discharge takes
precedence.
Charge Command Input. When low with DCMD high, the internal switch from ISET to BBATT is
7
CCMD
closed, charging the bridge battery. CCMD is inhibited if DCMD is low. The internal timer counts up
at a frequency set by the CC capacitor.
8
FULL
Open-Drain Bridge-Battery Full Indicator Output. When the internal timer reaches all 1sec, FULL
goes high impedance.
9
FB
Feedback Input of Step-Up DC-DC Converter. Regulates to 2V. Connect feedback resistors to set
output voltage (Figure 2).
10
LBI
Low-Battery-Detector Input. When LBI falls below 1.8V, LBO goes low and sinks current. When LBI
goes above 2.0V, LBO goes high impedance. Hysteresis is typically 200mV.
11
GND
Ground
Charge Oscillator Capacitor Input. This capacitor programs the charging oscillator frequency,
12 CC which sets the time for the internal counter to reach all 1s. Determine the capacitor value by: CC
(in nF) = 4.3 · charge time (in hours).
Discharge Oscillator Capacitor Input. This capacitor sets the discharging oscillator frequency,
13 CD which determines the maximum time to decrement the counter from all 1s to all 0s. Calculate the
capacitor value as follows: CD (in nF) = 4.3 · discharge time (in hours).
14
PGND
Power Ground and Step-Up DC-DC Converter N-Channel MOSFET Source
15
LRO
5V (MAX1612) or 3.3V (MAX1613) Linear-Regulator Output. Bypass to GND with a 1µF capacitor.
Maximum external load current is 10mA.
16 LRI Linear-Regulator Supply Input
_______________________________________________________________________________________ 5
5 Page 
Bridge-Battery Backup Controllers
for Notebooks
Table 5. Surface-Mount Inductor Information
MANUFACTURER
AND PART
Sumida CD43-8R2
Sumida CD43-150
Sumida CD54-100
Sumida CD54-150
Sumida CD54-220
INDUCTANCE
(µH)
8.2
15
10
15
22
RESISTANCE
(Ω)
0.132
0.235
0.100
0.140
0.180
RATED CURRENT
(A)
1.26
0.92
1.44
1.30
1.11
HEIGHT
(mm)
3.2
3.2
4.5
4.5
4.5
where VOUT is the DC-DC converter’s output voltage
and VTRIP is the voltage level the main battery must fall
below to trip the low-battery comparator. For example,
for a +5V boost DC-DC output, a 4.75V main battery
trip level is feasible. For this case, R1 = 750kΩ, R2 =
26kΩ, and R3 = 474kΩ.
Step 6: Select a resistor value to set the charging cur-
rent. The resistor value at ISET limits the current
through the switch for bridge-battery charging. There is
a voltage drop across the high-voltage switch (see
Electrical Characteristics) with a typical value of 1V.
The maximum charge current through the internal high-
voltage switch is 10mA.
RISET = (VCHARGE - VSWITCH - VBBATT) / ICHARGE
where VCHARGE is the charging supply voltage,
VSWITCH is the drop across the high-voltage internal
switch, VBBATT is the bridge battery voltage, and
ICHARGE is the charge current (in amperes).
Stand-Alone Application
To reduce cost and save space, the MAX1612/
MAX1613 can be operated in a stand-alone configura-
tion, which eliminates the need for a microcontroller. A
stand-alone configuration could also reduce the work-
load of an existing microcontroller in the system, thus
allowing these unused I/Os to be used for other appli-
cations.
Figure 3 shows the MAX1612/MAX1613 operating with-
out the microcontroller by using the low-battery detec-
tor to monitor the main battery. If the main battery is too
low, LBO pulls BBON and DCMD low to start the DC-
DC step-up converter and allow the bridge battery to
discharge. If the bridge battery requires charging,
FULL pulls CCMD low to start the battery charging
process. If both CCMD and DCMD are low, discharg-
ing takes precedence and the bridge battery keeps the
boost DC-DC converter active.
Microcontroller-Based Application
The MAX1612/MAX1613 are also suited to operate in a
microcontroller-based system. A microcontroller-based
application provides more flexibility by allowing for sep-
arate, independent control of the charging process, the
DC-DC converter, and the counter. Independent con-
trol can be beneficial in situations where other subsys-
tems are operating, so that automatic switchover of
power might create some timing issues. If necessary, a
microcontroller can be used to reset the counter by tak-
ing ISET low. Another advantage of a microcontroller-
based system is the ability to stop charging the bridge
battery during a fault condition.
Figure 4 shows an example of how the MAX1612/
MAX1613 can be interfaced to a MAX1630 to deliver
the input voltage to the main DC-DC converter. In this
example, the microcontroller monitors the main bat-
tery’s status and switches over to the bridge battery
when VMAIN falls below a specified trip level (see
Design Procedure). When VMAIN falls below the LBI
threshold, LBO goes low. This signals the microcon-
troller, via an I/O, to switch over to the bridge battery as
the input source to the system main DC-DC converter.
In this application, the microcontroller also initiates the
bridge-battery charging process. When CCMD goes
low with DCMD high, the battery is charged through the
internal switch. The counter increments until it overflows
and FULL goes high, indicating a full charge. The
microcontroller I/O can read and write the appropriate
states to control the execution and timing of the entire
process.
If the main DC-DC is supplied by the main source, the
MAX1612/MAX1613’s step-up converter turns off, mini-
mizing power consumption. The device typically draws
only 18µA of quiescent current under this condition.
______________________________________________________________________________________ 11
11 Page | ||
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| PDF Descargar | [ Datasheet MAX1612EEE.PDF ] | |
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