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PDF MAX8568A Data sheet ( Hoja de datos )
| Número de pieza | MAX8568A | |
| Descripción | (MAX8568A/B) Complete Backup-Management ICs | |
| Fabricantes | Maxim Integrated Products | |
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19-3450; Rev 1; 5/05
EVAALVUAAILTAIOBNLEKIT
Complete Backup-Management ICs
for Lithium and NiMH Batteries
General Description
The MAX8568A/MAX8568B backup-battery-management
ICs are complete charging and backup switchover con-
trol solutions for PDAs, Smart Phones, and other smart
portable devices. They charge both NiMH and
rechargeable lithium battery types and feature pro-
grammable charge current and termination voltage.
Separate optimized charge algorithms for both lithium
and NiMH cells are included on-chip.
The MAX8568A/MAX8568B also manage backup
switchover from a primary power source. An accurate on-
chip voltage detector monitors the main supply and
backs up two system supplies (typically I/O and memory)
when main power falls. On-chip drivers switch external
MOSFETs to disconnect the main supply from the system
loads so the backup source is not drained.
Low-voltage backup cells can be stepped up by an on-
chip synchronous-rectified, low-quiescent-current boost
converter. Additionally, a low-quiescent-current LDO gen-
erates a second backup voltage. The MAX8568A LDO is
preset to 2.5V while the MAX8568B LDO is preset to 1.8V.
Both devices are supplied in 16-pin 3mm x 3mm thin
QFN packages rated for -40°C to +85°C operation.
Applications
PDAs and PDA Phones
Smart Phones
DSCs and DVCs
Palmtops and Wireless Handhelds
Internet Appliances and Web-Books
Pin Configuration
TOP VIEW
12 11 10 9
GND 13
STRTV 14
TERMV 15
REF 16
MAX8568A
MAX8568B
8 OD2
7 OD1
6 LDO
5 BKSU
123 4
Features
♦ Automatically Manage All Backup Switchover
Functions
♦ Charge Both NiMH and Rechargeable Lithium
Backup Batteries
♦ On-Chip Battery Boost Converter for 1-Cell NiMH
♦ Two Backup Output Voltages
♦ Programmable Charge Current
♦ Programmable Charge Voltage Limit
♦ Low 17µA Operating Current in Backup Mode
♦ Eliminate Many Discrete Components
♦ Tiny 3mm x 3mm Thin QFN Package
Ordering Information
PART
TEMP RANGE
PIN-
PACKAGE
MAX8568AETE
-40°C to +85°C
16 Thin QFN
3mm x 3mm
(T1633-4)
MAX8568BETE
-40°C to +85°C
16 Thin QFN
3mm x 3mm
(T1633-4)
TOP
MARK
ACK
ACL
Typical Operating Circuit
MAIN BATTERY
2.8V TO 5.5V
BACKUP
BATTERY
I/O OUT
3.3V, 50mA
I/O IN
IN REF
BK MAX8568A
MAX8568B
TERMV
LX
BKSU
STRTV
PGND
GND
IN
MEM OUT
1.8V OR 2.5V, 10mA
MEM IN
BKV INOK
OD1 CHGI
LDO
THIN QFN
NI
OD2 NI/LI LI
________________________________________________________________ Maxim Integrated Products 1
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Datasheet pdf - http://www.DataSheet4U.net/
1 page  
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Complete Backup-Management ICs
for Lithium and NiMH Batteries
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 7, VIN = VINOK = 3.6V, VBK = 1.4V, VNI/LI = VBKSU = 3.3V, VBKV = GND = PGND = 0V, VSTRTV = VTERMV = 1.2V,
R5 = 250kΩ, TA = -40°C to +85°C, unless otherwise noted. Typical values are at TA = +25°C.) (Note 3)
PARAMETER
LX Current Limit (ILIM)
n-Channel Switch Maximum On-Time
p-Channel Zero-Channel Crossing Current
LOW-DROPOUT REGULATOR
BKSU Input Voltage Range
LDO Output-Voltage Accuracy
CONDITIONS
MIN
400
3.5
5
VBKSU = 3.3V
MAX8568A
MAX8568B
2.7
2.375
1.71
MAX
600
6.5
35
5.0
2.625
1.89
Note 1: All units are 100% production tested at TA = +25°C. Limits over the operating range are guaranteed by design.
Note 2: All backup step-up converter specifications are with VIN = VINOK = 0V, unless otherwise noted.
Note 3: Specifications to -40°C are guaranteed by design and not production tested.
UNITS
mA
µs
mA
V
V
Typical Operating Characteristics
(Circuit of Figure 7, VIN = 3.6V, VBK = 1.4V, VNI/LI = VBKSU = 3.3V, TA = +25°C, unless otherwise noted.)
NiMH CHARGE CURRENT
vs. BACKUP BATTERY VOLTAGE
12
10
8
6
FALLING
RISING
4
2
VIN = 3.9V
0
0 0.4 0.8 1.2 1.6
BACKUP BATTERY VOLTAGE (V)
2.0
LITHIUM CHARGE CURRENT
vs. BACKUP BATTERY VOLTAGE
14
12 VIN = 5V, VBK(LIMAX) = 4.2V
10
8
VIN = 3.9V
6 VBK(LIMAX) = 3.4V
4
2
0
0 0.6 1.2 1.8 2.4 3.0 3.6 4.2
BACKUP BATTERY VOLTAGE (V)
4.180
4.179
4.178
4.177
4.176
4.175
4.174
4.173
4.172
4.171
4.170
-40
Li-ION TERMINATION VOLTAGE
vs. TEMPERATURE
-15 10 35 60
TEMPERATURE (°C)
85
_______________________________________________________________________________________ 5
Datasheet pdf - http://www.DataSheet4U.net/
5 Page 
www.DataSheet.co.kr
Complete Backup-Management ICs
for Lithium and NiMH Batteries
The lithium charger acts like a current-limited voltage
source. The battery regulation voltage for lithium mode,
VBK(LIMAX), is:
VBK(LIMAX) = 3.5 x VTERMV
If VTERMV = 1.2V, then the final charge voltage is 4.2V.
Connect TERMV to a resistor-divider from REF to GND.
Adjust VTERMV with resistors R11 and R12 (Figure 2).
Select R12 to be in the 100kΩ to 1MΩ range. Calculate
R11 as follows:
R11 =
R12
3.5 × VREF
VBK(LIMAX)
− 1
where VREF =1.25V.
Using an NiMH Backup Battery
The MAX8568 can charge NiMH backup batteries from
the main battery connected at IN. Connect NI/LI to
BKSU for NiMH backup battery charging. VTERMV sets
the maximum cell voltage and also the trip point for the
fast-charge-to-trickle-charge transition. VSTRTV sets the
trickle-to-fast-charge transition threshold.
In NiMH charge mode (NI/LI connected to BKSU), the
charger ramps the battery between two thresholds
measured at the battery connection BK, VBK(NILO) and
VBK(NIHI). When the battery falls to VBK(NILO), trickle
charging stops and fast charging starts. When the bat-
tery rises to VBK(NIHI), fast charging stops and trickle
charging begins. If, for any reason, the battery contin-
ues to rise when trickle charged, all charging ceases at
VBK(NIMAX). VBK(NILO), VBK(NIHI), and VBK(NIMAX) are
set as follows:
BK voltage where fast charge begins:
VBK(NILO) = VSTRTV
BK voltage where trickle charge begins:
VBK(NIHI) = 1.163 x VTERMV
BK voltage where all charging stops:
VBK(NIMAX) = 1.493 x VTERMV
Resistor-dividers (see Figure 3) set VSTRTV and VTERMV
by dividing down REF. To minimize operating current,
resistors between 100kΩ and 1MΩ should be used for
R14 and R16 in Figure 3. The formulas for the upper
divider-resistors in terms of VBK(NILO), VBK(NIHI), and
VBK(NIMAX) are:
R13
=
R14
VREF
VBK(NILO)
− 1
R15
=
R16
1.163 × VREF
VBK(NIHI)
− 1
Once VBK(NIHI) is selected, the maximum battery volt-
age is:
VBK(NIMAX) = 1.283 x VBK(NIHI)
16
REF
15
TERMV
14
STRTV
R11
R12
Figure 2. Resistor-Divider for Setting the Maximum Battery
Voltage, VBK(LIMAX), for Rechargeable Lithium-Type Backup
Batteries
16
REF
15
TERMV
14
STRTV
R13 R15
R16
R14
Figure 3. 2-Resistor-Dividers for Setting VBK(NILO) and VBK(NIHI)
______________________________________________________________________________________ 11
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| PDF Descargar | [ Datasheet MAX8568A.PDF ] | |
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