MAX6909 MAXIM [Maxim Integrated Products], MAX6909 Datasheet - Page 17

• Manufacturer Part Number: MAX6909
• Description: I2C-Compatible Real-Time Clocks with uP Supervisor and NV RAM Controller
• Manufacturer: MAXIM [Maxim Integrated Products]

Table 3. Hex Register Address/Description (continued)
Diode and resistor selection is determined by the user,
according to the maximum current desired for the battery
or SuperCap charging. The maximum charging current
can be calculated as shown in the following example.
Assume that a system power supply of 3V is applied to
V
that the trickle charger has been enabled with no diode
and resistor R1 between V
current I
As the SuperCap charges, the voltage difference
between V
charge current decreases. The MAX6909 does not fea-
ture a trickle charger.
BATT provides power as a battery backup. V
the primary power in dual-supply systems where BATT is
connected as a backup source to maintain the timekeep-
ing function and RAM + register contents. When V
rises above the reset threshold, V
MAX6909/MAX6910. When V
CC
WRITE (HEX)
and a SuperCap is connected to BATT. Also assume
EA
EC
FC
E4
E6
E8
EE
F0
F2
F4
F6
F8
FA
FE
MAX
Power Control, Trickle Charger, and
CC
would therefore be calculated as follows:
I
MAX
and V
I
READ (HEX)
2
______________________________________________________________________________________
=
C-Compatible Real-Time Clocks with µP
BATT
ED
E5
E7
E9
EB
EF
FB
FD
3 0
F1
F3
F5
F7
F9
FF
R
.
1
V
decreases, and therefore the
CC
≈
1 7
3 0
.
and BATT. The maximum
CC
Battery Switchover
.
RAM 18
RAM 19
RAM 20
RAM 21
RAM 22
RAM 23
RAM 24
RAM 25
RAM 26
RAM 27
RAM 28
RAM 29
RAM 30
RAM Burst
k
Supervisor and NV RAM Controller
V
Ω
falls below the reset
RST
≈
1 76
, V
.
DESCRIPTION
CC
mA
CC
powers the
provides
CC
threshold, VRST, and is less than V
MAX6909/MAX6910. If V
old, V
MAX6909/MAX6910. When RESET and RESET are active,
all inputs (MR, WDI, CE IN, and the 2-wire interface) are
disabled. In addition, when operating from BATT, the out-
puts RESET, RESET, and PFO remain in the active state,
PZT is high impedance and CE OUT is pulled to OUT.
The timekeeping function remains active, together with
the alarm function and crystal fail function if enabled. To
minimize power consumption when operating from BATT,
some functions are disabled; see Table 5. MAX6909/
MAX6910 functional blocks remain active when powered
from V
A battery can be connected prior to application of V
with no current being drawn from the battery and the
MAX6909/MAX6910 remaining inactive. This is the
freshness seal mode of operation. On the very first
application of V
must rise above the reset threshold. The battery should
only be changed with V
timekeeping functions.
The trickle charger can be enabled and disabled
through software control but is automatically disabled
whenever V
POR CONTENTS (HEX)
CC
RST
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
or BATT.
, and is more than V
CC
N/A
falls below V
CC
to the MAX6909/MAX6910, V
CC
CC
applied in order to maintain
BATT
falls below the reset thresh-
POR CONTENTS (BCD)
.
TPD
TPD
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
Indeterminate
, V
, BATT powers the
CC
N/A
powers the
CC
CC
17