MAX8568AETE+ Maxim Integrated Products, MAX8568AETE+ Datasheet - Page 11

• Manufacturer Part Number: MAX8568AETE+
• Description: IC BATT MANAGE LITH 16-TQFN
• Manufacturer: Maxim Integrated Products

Specifications of MAX8568AETE+

• Function: Back-Up Management
• Battery Type: Lithium-Ion (Li-Ion); Nickel-Metal Hydride (NiMH)
• Voltage - Supply: 2.8 V ~ 5.5 V
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 16-TQFN Exposed Pad
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The lithium charger acts like a current-limited voltage
source. The battery regulation voltage for lithium mode,
V
If V
Connect TERMV to a resistor-divider from REF to GND.
Adjust V
Select R12 to be in the 100kΩ to 1MΩ range. Calculate
R11 as follows:
where V
The MAX8568 can charge NiMH backup batteries from
the main battery connected at IN. Connect NI/LI to
BKSU for NiMH backup battery charging. V
the maximum cell voltage and also the trip point for the
fast-charge-to-trickle-charge transition. V
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, V
V
charging stops and fast charging starts. When the bat-
tery rises to V
charging begins. If, for any reason, the battery contin-
Figure 2. Resistor-Divider for Setting the Maximum Battery
Voltage, V
Batteries
BK(LIMAX)
BK(NIHI)
TERMV
REF
TERMV
BK(LIMAX)
. When the battery falls to V
= 1.2V, then the final charge voltage is 4.2V.
, is:
=1.25V.
R
V
BK(NIHI)
11
Using an NiMH Backup Battery
BK(LIMAX)
with resistors R11 and R12 (Figure 2).
, for Rechargeable Lithium-Type Backup
______________________________________________________________________________________
=
R
TERMV
, fast charging stops and trickle
STRTV
12
REF



= 3.5 x V
V
3 5
16
15
14
BK LIMAX
.
Complete Backup-Management ICs
(
×
V
REF
TERMV
)
BK(NILO)
−
R11
R12
for Lithium and NiMH Batteries
STRTV
1



BK(NILO)
TERMV
sets the
, trickle
sets
and
ues to rise when trickle charged, all charging ceases at
V
set as follows:
Resistor-dividers (see Figure 3) set V
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 V
V
Once V
age is:
Figure 3. 2-Resistor-Dividers for Setting V
BK(NIMAX)
BK(NIMAX)
BK voltage where fast charge begins:
BK voltage where trickle charge begins:
BK voltage where all charging stops:
BK(NIHI)
. V
are:
V
R
BK(NIMAX)
R
V
15
BK(NILO)
V
13
BK(NIMAX)
is selected, the maximum battery volt-
BK(NIHI)
=
V
=
TERMV
STRTV
R
BK(NILO)
16
R
REF
, V
14
= 1.283 x V



= 1.163 x V
16
15
14
1 163
BK(NIHI)



= 1.493 x V
.
V
V
BK NILO
BK NIHI
= V
V
BK(NILO)
REF
(
(
×
STRTV
, and V
V
REF
R13
R14
BK(NIHI)
BK(NILO)
)
)
TERMV
STRTV
TERMV
−
, V
1
−



BK(NIMAX)
1
BK(NIHI)
R15
R16



and V
and V
BK(NIHI)
TERMV
, and
are
11