TI BQ3285LSSTR Real-time clock rtc Datasheet

bq3285E/L
Real-Time Clock (RTC)
Features
➤ BCD or binary format for clock
and calendar data
General Description
➤ Direct clock/calendar replacement for IBM® AT-compatible
computers and other applications
➤ Calendar in day of the week, day
of the month, months, and years,
with automatic leap-year adjustment
The CMOS bq3285E/L is a lowpower microprocessor peripheral
providing a time-of-day clock and
100-year calendar with alarm features and battery operation. The
bq3285L supports 3V systems.
Other bq3285E/L features include
three maskable interrupt sources,
square-wave output, and 242 bytes
of general nonvolatile storage.
➤ Functionally compatible with the
DS1285
-
Closely matches MC146818A
pin configuration
➤ Time of day in seconds, minutes,
and hours
-
➤ 2.7–3.6V operation (bq3285L);
4.5–5.5V operation (bq3285E)
12- or 24-hour format
Optional daylight saving
adjustment
➤ 242 bytes of general nonvolatile
storage
➤ Programmable square wave output
➤ 32.768kHz output for power management
➤ Three individually maskable interrupt event flags:
➤ System wake-up capability—
alarm interrupt output active in
battery-backup mode
➤ Less than 0.5µA load under battery operation
➤ Selectable Intel or Motorola bus
timing
-
Periodic rates from 122µs to
500ms
-
Time-of-day alarm once per
second to once per day
-
End-of-clock update cycle
➤ 24-pin plastic DIP, SOIC, or
SSOP
➤ 14 bytes for clock/calendar and
control
Pin Connections
1
2
3
4
5
6
7
8
9
10
11
12
24
23
22
21
20
19
18
17
16
15
14
13
The bq3285E/L write-protects the
clock, calendar, and storage registers
during power failure. A backup
battery then maintains data and operates the clock and calendar.
The bq3285E/L is a fully compatible
real-time clock for IBM AT-compatible
computers and other applications.
The only external components are a
32.768kHz crystal and a backup battery.
Pin Names
AD0–AD7
MOT
X1
X2
AD0
AD1
AD2
AD3
AD4
AD5
AD6
AD7
VSS
A 32.768kHz output is available for
sustaining power-management activities. Wake-up capability is provided by an alarm interrupt, which
is active in battery-backup mode.
VCC
SQW
EXTRAM
RCL
BC
INT
RST
DS
VSS
R/W
AS
CS
Multiplexed address/
RST
Reset input
data input/output
SQW
Square wave output
MOT
Bus type select input
EXTRAM Extended RAM enable
CS
Chip select input
RCL
RAM clear input
AS
Address strobe input
BC
3V backup cell input
DS
Data strobe input
X1–X2
Crystal inputs
R/W
Read/write input
VCC
Power supply
INT
Interrupt request
VSS
Ground
output
24-Pin DIP or SOIC/SSOP
PN3285E1.eps
SLUS004A -DECEMBER 1993 - REVISED MAY 2004
1
bq3285E/L
Block Diagram
AD0–AD7
Pin Descriptions
MOT
Bus type select input
The bq3285E/L bus cycle consists of two
phases: the address phase and the datatransfer phase. The address phase precedes the data-transfer phase. During the
address phase, an address placed on
AD0–AD7 and EXTRAM is latched into the
bq3285E/L on the falling edge of the AS signal. During the data-transfer phase of the
bus cycle, the AD0–AD7 pins serve as a bidirectional data bus.
MOT selects bus timing for either Motorola
or Intel architecture. This pin should be
tied to VCC for Motorola timing or to VSS for
Intel timing (see Table 1). The setting
should not be changed during system operation. MOT is internally pulled low by a
30KΩ resistor.
Table 1. Bus Setup
AS
Bus
Type
MOT
DS
R/W
AS
Level Equivalent Equivalent Equivalent
Motorola
VCC
DS, E, or
Φ2
R/W
Intel
VSS
RD,
MEMR, or
I/OR
WR,
MEMW, or ALE
I/OW
Multiplexed address/data input/
output
Address strobe input
AS serves to demultiplex the address/data
bus. The falling edge of AS latches the address on AD0–AD7 and EXTRAM. This demultiplexing process is independent of the
CS signal. For DIP and SOIC packages with
MOT = VSS, the AS input is provided a signal
similar to ALE in an Intel-based system.
AS
2
bq3285E/L
DS
EXTRAM
Data strobe input
Enables 128 bytes of additional nonvolatile
SRAM. It is connected internally to a 30K
Ω pull-down resistor. To access the RTC
registers, EXTRAM must be low.
When MOT = VCC, DS controls data transfer during a bq3285E/L bus cycle. During a
read cycle, the bq3285E/L drives the bus after the rising edge on DS. During a write
cycle, the falling edge on DS is used to latch
write data into the chip.
RCL
Read/write input
When MOT = VCC, the level on R/W identifies the direction of data transfer. A high
level on R/W indicates a read bus cycle,
whereas a low on this pin indicates a write
bus cycle.
BC
When MOT = VSS, R/W is provided a signal similar to WR, MEMW, or I/OW in an
Intel-based system. The rising edge on
R/W latches data into the bq3285E/L.
CS
Chip select input
Upon power-up, a voltage within the VBC
range must be present on the BC pin for
the oscillator to start up.
Interrupt request output
INT is an open-drain output. This allows
alarm INT to be valid in battery-backup
mode. To use this feature, INT must be connected to a power supply other than VCC.
INT is asserted low when any event flag is
set and the corresponding event enable bit
is also set. INT becomes high-impedance
whenever register C is read (see the Control/Status Registers section).
SQW
3V backup cell input
BC should be connected to a 3V backup cell
for RTC operation and storage register nonvolatility in the absence of system power.
When VCC slews down past VBC (3V typical),
the integral control circuitry switches the
power source to BC. When VCC returns
above VBC, the power source is switched to
VCC.
CS should be driven low and held stable
during the data-transfer phase of a bus cycle accessing the bq3285E/L.
INT
RAM clear input
A low level on the RCL pin causes the contents of each of the 242 storage bytes to be
set to FF(hex). The contents of the clock
and control registers are unaffected. This
pin should be used as a user-interface input
(pushbutton to ground) and not connected
to the output of any active component. RCL
input is only recognized when held low for
at least 125ms in the presence of VCC. Using RAM clear does not affect the battery
load. This pin is connected internally to a
30KΩ pull-up resistor.
When MOT = VSS, the DS input is provided
a signal similar to RD, MEMR, or I/OR in
an Intel-based system. The falling edge on
DS is used to enable the outputs during a
read cycle.
R/W
Extended RAM enable
RST
Reset input
The bq3285E/L is reset when RST is pulled
low. When reset, INT becomes high impedance, and the bq3285E/L is not accessible.
Table 4 in the Control/Status Registers section lists the register bits that are cleared
by a reset.
Square-wave output
Reset may be disabled by connecting RST
to VCC. This allows the control bits to reta i n th e i r s ta te s th ro u g h p o w erdown/power-up cycles.
SQW may output a programmable frequency square-wave signal during normal
(VCC valid) system operation. Any one of
the 13 specific frequencies may be selected
through register A. This pin is held low
when the square-wave enable bit (SQWE)
in register B is 0 (see the Control/Status
Registers section).
X1–X2
Crystal inputs
The X1–X2 inputs are provided for an external 32.768kHz quartz crystal, Daiwa DT-26
or equivalent, with 6pF load capacitance. A
trimming capacitor may be necessary for extremely precise time-base generation.
A 32.768kHz output is enabled by setting
the SQWE bit in register B to 1 and the
32KE bit in register C to 1 after setting
OSC2–OSC0 in register A to 011 (binary).
In the absence of a crystal, a 32.768kHz
waveform can be fed into the X1 input.
3
bq3285E/L
dar locations during the update cycle at the end of each
update period (see Figure 2). The alarm flag bit may
also be set during the update cycle.
Functional Description
Address Map
The bq3285E/L copies the local register updates into the
user buffer accessed by the host processor. When a 1 is
written to the update transfer inhibit bit (UTI) in register B, the user copy of the clock and calendar bytes remains unchanged, while the local copy of the same bytes
continues to be updated every second.
The bq3285E/L provides 14 bytes of clock and control/status registers and 242 bytes of general nonvolatile
storage. Figure 1 illustrates the address map for the
bq3285E/L.
Update Period
The update-in-progress bit (UIP) in register A is set
tBUC time before the beginning of an update cycle (see
Figure 2). This bit is cleared and the update-complete
flag (UF) is set at the end of the update cycle.
The update period for the bq3285E/L is one second. The
bq3285E/L updates the contents of the clock and calen-
Figure 1. Address Map
Figure 2. Update Period Timing and UIP
4
bq3285E/L
c.
Programming the RTC
Write the appropriate value to the hour
format (HF) bit.
The time-of-day, alarm, and calendar bytes can be written in either the BCD or binary format (see Table 2).
2.
Write new values to all the time, alarm, and
calendar locations.
These steps may be followed to program the time, alarm,
and calendar:
3.
Clear the UTI bit to allow update transfers.
1.
On the next update cycle, the RTC updates all 10 bytes
in the selected format.
Modify the contents of register B:
a.
Write a 1 to the UTI bit to prevent transfers between RTC bytes and user buffer.
b.
Write the appropriate value to the data
format (DF) bit to select BCD or binary
format for all time, alarm, and calendar
bytes.
Table 2. Time, Alarm, and Calendar Formats
Range
Address
RTC Bytes
Decimal
Binary
Binary-Coded
Decimal
0
Seconds
0–59
00H–3BH
00H–59H
1
Seconds alarm
0–59
00H–3BH
00H–59H
2
Minutes
0–59
00H–3BH
00H–59H
3
Minutes alarm
0–59
00H–3BH
00H–59H
Hours, 12-hour format
1–12
01H–OCH AM;
81H–8CH PM
01H–12H AM;
81H–92H PM
Hours, 24-hour format
0–23
00H–17H
00H–23H
Hours alarm, 12-hour format
1–12
01H–OCH AM;
81H–8CH PM
01H–12H AM;
81H–92H PM
Hours alarm, 24-hour format
0–23
00H–17H
00H–23H
6
Day of week (1=Sunday)
1–7
01H–07H
01H–07H
7
Day of month
1–31
01H–1FH
01H–31H
8
Month
1–12
01H–0CH
01H–12H
9
Year
0–99
00H–63H
00H–99H
4
5
5
bq3285E/L
Square-Wave Output
n
The bq3285E/L divides the 32.768kHz oscillator frequency to produce the 1Hz update frequency for the
clock and calendar. Thirteen taps from the frequency divider are fed to a 16:1 multiplexer circuit. The output of
this mux is fed to the SQW output and periodic interrupt generation circuitry. The four least-significant bits
of register A, RS0–RS3, select among the 13 taps (see
Table 3). The square-wave output is enabled by writing
a 1 to the square-wave enable bit (SQWE) in register B.
A 32.768kHz output may be selected by setting
OSC2–OSC0 in register A to 011 while SQWE = 1 and
32KE = 1.
n
The update-ended interrupt, which occurs at the end
of each update cycle.
Each of the three interrupt events is enabled by an individual interrupt-enable bit in register B. When an event
occurs, its event flag bit in register C is set. If the corresponding event enable bit is also set, then an interrupt
request is generated. The interrupt request flag bit
(INTF) of register C is set with every interrupt request.
Reading register C clears all flag bits, including INTF,
and makes INT high-impedance.
Two methods can be used to process bq3285E/L interrupt
events:
Interrupts
n
The bq3285E/L allows three individually selected interrupt events to generate an interrupt request. These
three interrupt events are:
n
The alarm interrupt, programmable to occur once per
second to once per day, is active in battery-backup
mode, providing a “wake-up” feature.
n
The periodic interrupt, programmable to occur once
every 122µs to 500ms.
Enable interrupt events and use the interrupt request
output to invoke an interrupt service routine.
Do not enable the interrupts and use a polling routine
to periodically check the status of the flag bits.
The individual interrupt sources are described in detail
in the following sections.
Table 3. Square-Wave Frequency/Periodic Interrupt Rate
Register A Bits
Square Wave
OSC1
OSC0
RS3
RS2
RS1
RS0
0
1
0
0
0
0
0
0
1
0
0
0
0
1
256
Hz
3.90625
ms
0
1
0
0
0
1
0
128
Hz
7.8125
ms
0
1
0
0
0
1
1
8.192
kHz
122.070
µs
0
1
0
0
1
0
0
4.096
kHz
244.141
µs
0
1
0
0
1
0
1
2.048
kHz
488.281
µs
0
1
0
0
1
1
0
1.024
kHz
976.5625
µs
0
1
0
0
1
1
1
512
Hz
1.95315
ms
0
1
0
1
0
0
0
256
Hz
3.90625
ms
0
1
0
1
0
0
1
128
Hz
7.8125
ms
0
1
0
1
0
1
0
64
Hz
15.625
ms
0
1
0
1
0
1
1
32
Hz
31.25
ms
0
1
0
1
1
0
0
16
Hz
62.5
ms
0
1
0
1
1
0
1
8
Hz
125
ms
0
1
0
1
1
1
0
4
Hz
250
ms
0
1
0
1
1
1
1
2
Hz
500
ms
0
1
1
X
X
X
Frequency
Units
Periodic Interrupt
OSC2
None
X
6
32.768
Period
Units
None
kHz
same as above defined
by RS3–RS0
bq3285E/L
Periodic Interrupt
Update Cycle Interrupt
The mux output used to drive the SQW output also
drives the interrupt-generation circuitry. If the periodic
interrupt event is enabled by writing a 1 to the periodic
interrupt enable bit (PIE) in register C, an interrupt request is generated once every 122µs to 500ms. The period between interrupts is selected by the same bits in
register A that select the square wave frequency (see Table 3). Setting OSC2–OSC0 in register A to 011 does not
affect the periodic interrupt timing.
The update cycle ended flag bit (UF) in register C is set to
a 1 at the end of an update cycle. If the update interrupt
enable bit (UIE) of register B is 1, and the update transfer
inhibit bit (UTI) in register B is 0, then an interrupt request
is generated at the end of each update cycle.
Accessing RTC bytes
The EXTRAM pin must be low to access the RTC registers. Time and calendar bytes read during an update
cycle may be in error. Three methods to access the time
and calendar bytes without ambiguity are:
Alarm Interrupt
The alarm interrupt is active in battery-backup mode,
providing a “wake-up” capability. During each update
cycle, the RTC compares the hours, minutes, and seconds bytes with the three corresponding alarm bytes. If
a match of all bytes is found, the alarm interrupt event
flag bit, AF in register C, is set to 1. If the alarm event
is enabled, an interrupt request is generated.
n
n
An alarm byte may be removed from the comparison by
setting it to a “don’t care” state. An alarm byte is set to
a “don’t care” state by writing a 1 to each of its two
most-significant bits. A “don’t care” state may be used to
select the frequency of alarm interrupt events as follows:
n
n
n
n
n
If none of the three alarm bytes is “don’t care,” the
frequency is once per day, when hours, minutes, and
seconds match.
If only the hour alarm byte is “don’t care,” the
frequency is once per hour, when minutes and
seconds match.
Enable the update interrupt event to generate
interrupt requests at the end of the update cycle. The
interrupt handler has a maximum of 999ms to access
the clock bytes before the next update cycle begins (see
Figure 3).
Poll the update-in-progress bit (UIP) in register A. If
UIP = 0, the polling routine has a minimum of tBUC
time to access the clock bytes (see Figure 3).
Use the periodic interrupt event to generate
interrupt requests every tPI time, such that UIP = 1
always occurs between the periodic interrupts. The
interrupt handler has a minimum of tPI/2 + tBUC
time to access the clock bytes (see Figure 3).
Oscillator Control
When power is first applied to the bq3285E/L and VCC is
above VPFD, the internal oscillator and frequency divider
are turned on by writing a 010 pattern to bits 4 through 6
of register A. A pattern of 011 behaves as 010 but additionally transforms register C into a read/write register. This
allows the 32.768kHz output on the square wave pin to be
turned on. A pattern of 11X turns the oscillator on, but
keeps the frequency divider disabled. Any other pattern to
these bits keeps the oscillator off.
If only the hour and minute alarm bytes are “don’t
care,” the frequency is once per minute, when seconds
match.
If the hour, minute, and second alarm bytes are
“don’t care,” the frequency is once per second.
Figure 3. Update-Ended/Periodic Interrupt Relationship
7
bq3285E/L
Register A provides:
Power-Down/Power-Up Cycle
n
The bq3285E and bq3285L power-up/power-down cycles are
different. The bq3285L continuously monitors VCC for out-oftolerance. During a power failure, when VCC falls below VPFD
(2.53V typical), the bq3285L write-protects the clock and storage registers. The power source is switched to BC when VCC is
less than VPFD and BC is greater than VPFD, or when VCC is
less than VBC and VBC is less than VPFD. RTC operation and
storage data are sustained by a valid backup energy source.
When VCC is above VPFD, the power source is VCC. Writeprotection continues for tCSR time after VCC rises above VPFD.
RS0–RS3 - Frequency Select
7
-
7
-
0
RS0
n
2
RS2
1
RS1
0
RS0
5
OS1
4
OS0
3
-
2
-
1
-
0
-
6
-
5
-
4
-
3
-
2
-
1
-
0
-
This read-only bit is set prior to the update cycle. When
UIP equals 1, an RTC update cycle may be in progress.
UIP is cleared at the end of each update cycle. This bit
is also cleared when the update transfer inhibit (UTI)
bit in register B is 1.
Register A programs:
n
6
OS2
7
UIP
1
RS1
3
RS3
UIP - Update Cycle Status
Register A
Register A Bits
4
3
2
OS0 RS3 RS2
4
-
These three bits control the state of the oscillator and
divider stages. A pattern of 010 enables RTC operation
by turning on the oscillator and enabling the frequency
divider. A pattern of 011 behaves as 010 but additionally
transforms register C into a read/write register. This allows the 32.768kHz output on the square wave pin to be
turned on. A pattern of 11X turns the oscillator on, but
keeps the frequency divider disabled. When 010 is written, the RTC begins its first update after 500ms.
The four control/status registers of the bq3285E/L are
accessible regardless of the status of the update cycle
(see Table 4).
5
OS1
5
-
OS0–OS2 - Oscillator Control
Control/Status Registers
6
OS2
6
-
These bits select one of the 13 frequencies for the SQW output and the periodic interrupt rate, as shown in Table 3.
The bq3285E continuously monitors VCC for out-of-tolerance.
During a power failure, when VCC falls below VPFD (4.17V
typical), the bq3285E write-protects the clock and storage
registers. When VCC is below VBC (3V typical), the power
source is switched to BC. RTC operation and storage data
are sustained by a valid backup energy source. When VCC is
above VBC, the power source is VCC. Write-protection continues for tCSR time after VCC rises above VPFD.
7
UIP
Status of the update cycle.
The frequency of the square-wave and the periodic
event rate.
Oscillator operation.
Table 4. Control/Status Registers
Loc.
Reg. (Hex) Read Write
1
Bit Name and State on Reset
7 (MSB)
6
5
4
3
2
A
0A
Yes
Yes
UIP
na OS2 na OS1 na OS0 na
B
0B
Yes
Yes
UTI
na
PIE
0
AIE
0
UIE
0 SQWE
0
C
0C
Yes
No2 INTF
0
PF
0
AF
0
UF
0
-
0
D
0D
Yes
No
na
-
0
-
0
-
0
-
0
Notes:
VRT
RS3
0 (LSB)
na RS2 na RS1 na
na = not affected.
1. Except bit 7.
2. Read/write only when OSC2–OSC0 in register A is 011 (binary).
8
1
DF
na
32KE na
-
0
HF
RS0 na
na DSE na
-
0
-
0
-
0
-
0
bq3285E/L
SQWE - Square-Wave Enable
Register B
7
UTI
6
PIE
5
AIE
Register B Bits
4
3
2
UIE SQWE DF
1
HF
7
-
0
DSE
6
-
5
-
4
-
3
SQWE
2
-
1
-
0
-
1
-
0
-
This bit enables the square-wave output:
Register B enables:
1 = Enabled
n
Update cycle transfer operation
n
Square-wave output
n
Interrupt events
n
Daylight saving adjustment
0 = Disabled and held low
UIE - Update Cycle Interrupt Enable
7
-
6
-
5
-
4
UIE
3
-
2
-
Register B selects:
n
This bit enables an interrupt request due to an update
ended interrupt event:
Clock and calendar data formats
All bits of register B are read/write.
1 = Enabled
DSE - Daylight Saving Enable
7
-
6
-
5
-
4
-
0 = Disabled
3
-
2
-
1
-
0
DSE
The UIE bit is automatically cleared when the UTI bit
equals 1.
AIE - Alarm Interrupt Enable
This bit enables daylight-saving time adjustments when
written to 1:
n
n
7
-
On the last Sunday in October, the first time the
bq3285E/L increments past 1:59:59 AM, the time
falls back to 1:00:00 AM.
5
-
4
-
3
-
2
-
1
HF
0
-
7
-
1
-
0
-
6
PIE
5
-
4
-
3
-
2
-
1
-
0
-
This bit enables an interrupt request due to a periodic
interrupt event:
0 = 12-hour format
1 = Enabled
DF - Data Format
5
-
2
-
PIE - Periodic Interrupt Enable
1 = 24-hour format
6
-
3
-
0 = Disabled
This bit selects the time-of-day and alarm hour format:
7
-
4
-
1 = Enabled
HF - Hour Format
6
-
5
AIE
This bit enables an interrupt request due to an alarm
interrupt event:
On the first Sunday in April, the time springs
forward from 2:00:00 AM to 3:00:00 AM.
7
-
6
-
0 = Disabled
4
-
3
-
2
DF
1
-
0
-
This bit selects the numeric format in which the time,
alarm, and calendar bytes are represented:
1 = Binary
0 = BCD
9
bq3285E/L
UTI - Update Transfer Inhibit
7
UTI
6
-
5
-
4
-
PF - Periodic Event Flag
3
-
2
-
1
-
This bit is set to a 1 every tPI time, where tPI is the time
period selected by the settings of RS0–RS3 in register A.
Reading register C clears this bit.
0
-
7
-
This bit inhibits the transfer of RTC bytes to the user
buffer:
6
PF
5
-
4
-
3
-
2
-
1
-
0
-
1 = Inhibits transfer and clears UIE
INTF - Interrupt Request Flag
0 = Allows transfer
This flag is set to a 1 when any of the following is true:
Register C
AIE = 1 and AF = 1
PIE = 1 and PF = 1
7
6
5
INTF
-
Register C is the read-only event status register.
7
INTF
6
PF
Register C Bits
5
4
3
2
AF
UF
0
32KE
1
0
0
0
4
-
3
-
2
-
1
-
0
-
UIE = 1 and UF = 1
Bits 0, 1, 3 - Unused Bits
Reading register C clears this bit.
These bits are always set to 0.
Register D
Register D is the read-only data integrity status register.
7
-
6
-
5
-
4
-
3
0
2
-
1
0
0
0
Bits 0–6 - Unused Bits
These bits are always set to 0.
32KE - 32kHz Enable Output
VRT - Valid RAM and Time
Register D Bits
7
6
5
4
3
VRT
0
0
0
0
This bit may be set to a 1 only when the OSC2–OSC0
bits in register A are set to 011. Setting OSC2–OSC0 to
7
-
6
-
5
-
4
-
3
-
2
32KE
1
-
0
-
2
0
1
0
0
0
1
0
0
0
1 = Valid backup energy source
anything other than 011 clears this bit. If SQWE in register B and 32KE are set, a 32.768kHz waveform is output on the square wave pin.
0 = Backup energy source is depleted
7
-
UF - Update Event Flag
This bit is set to a 1 at the end of the update cycle.
7
-
6
-
5
-
4
UF
3
-
2
-
1
-
0
-
AF - Alarm Event Flag
This bit is set to a 1 when an alarm event occurs. Reading register C clears this bit.
7
-
6
-
5
AF
4
-
3
-
2
-
1
-
0
-
10
5
0
4
0
3
0
2
0
When the backup energy source is depleted (VRT = 0),
data integrity of the RTC and storage registers is not
guaranteed.
7
VRT
Reading register C clears this bit.
6
0
6
-
5
-
4
-
3
-
2
-
1
-
0
-
bq3285E/L
Absolute Maximum Ratings—bq3285E
Symbol
Parameter
Value
Unit
Conditions
VCC
DC voltage applied on VCC relative to VSS
-0.3 to 7.0
V
VT
DC voltage applied on any pin excluding VCC
relative to VSS
-0.3 to 7.0
V
VT ≤ VCC + 0.3
TOPR
0 to +70
°C
Commercial
Operating temperature
TSTG
Storage temperature
-55 to +125
°C
TBIAS
Temperature under bias
-40 to +85
°C
TSOLDER
Soldering temperature
260
°C
Note:
For 10 seconds
Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability.
Absolute Maximum Ratings—bq3285L
Symbol
Parameter
Value
Unit
Conditions
VCC
DC voltage applied on VCC relative to VSS
-0.3 to 6.0
V
VT
DC voltage applied on any pin excluding VCC
relative to VSS
-0.3 to 6.0
V
VT ≤ VCC + 0.3
TOPR
Operating temperature
0 to +70
°C
Commercial
TSTG
Storage temperature
-55 to +125
°C
TBIAS
Temperature under bias
-40 to +85
°C
TSOLDER
Soldering temperature
260
°C
Note:
For 10 seconds
Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional operation should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Exposure to conditions beyond the operational limits for extended periods of time may affect device reliability.
11
bq3285E/L
Recommended DC Operating Conditions—bq3285E (TA = TOPR)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
VCC
Supply voltage
4.5
5.0
5.5
V
VSS
Supply voltage
0
0
0
V
VIL
Input low voltage
-0.3
-
0.8
V
VIH
Input high voltage
2.2
-
VCC + 0.3
V
VBC
Backup cell voltage
2.5
-
4.0
V
Note:
Typical values indicate operation at TA = 25°C.
Recommended DC Operating Conditions—bq3285L (TA = TOPR)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
VCC
Supply voltage
2.7
3.15
3.6
V
VSS
Supply voltage
0
0
0
V
VIL
Input low voltage
-0.3
-
0.6
V
VIH
Input high voltage
2.2
-
VCC + 0.3
V
VBC
Backup cell voltage
2.4
-
4.0
V
Note:
Typical values indicate operation at TA = 25°C.
Crystal Specifications—bq3285E/L (DT-26 or Equivalent)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
-
32.768
-
kHz
6
-
pF
25
30
°C
-0.042
ppm/°C
fO
Oscillation frequency
CL
Load capacitance
-
TP
Temperature turnover point
20
k
Parabolic curvature constant
-
-
Q
Quality factor
40,000
70,000
-
R1
Series resistance
-
-
45
KΩ
pF
C0
Shunt capacitance
-
1.1
1.8
C0/C1
Capacitance ratio
-
430
600
DL
Drive level
-
-
1
µW
∆f/fO
Aging (first year at 25°C)
-
1
-
ppm
12
bq3285E/L
DC Electrical Characteristics—bq3285E (TA = TOPR, VCC = 5V ± 10%)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
Conditions/Notes
ILI
Input leakage current
-
-
±1
µA
VIN = VSS to VCC
ILO
Output leakage current
-
-
±1
µA
AD0–AD7, INT, and SQW
in high impedance,
VOUT = VSS to VCC
VOH
Output high voltage
2.4
-
-
V
IOH = -2.0 mA
VOL
Output low voltage
-
-
0.4
V
IOL = 4.0 mA
ICC
Operating supply current
-
7
15
mA
Min. cycle, duty = 100%,
IOH = 0mA, IOL = 0mA
ICCSB
Standby supply current
-
300
-
µA
VIN = VSS or VCC,
CS ≥ VCC - 0.2
VSO
Supply switch-over voltage
-
VBC
-
V
ICCB
Battery operation current
-
0.3
0.5
µA
VPFD
Power-fail-detect voltage
4.0
4.17
4.35
V
IRCL
Input current when RCL = VSS.
-
-
185
µA
Internal 30K pull-up
Input current when MOT = VCC
-
-
-185
µA
Internal 30K pull-down
Input current when MOT = VSS
-
-
0
µA
Internal 30K pull-down
Input current when EXTRAM =
VCC
-
-
-185
µA
Internal 30K pull-down
Input current when EXTRAM =
VSS
-
-
0
µA
Internal 30K pull-down
VBC = 3V, TA = 25°C
IMOTH
IXTRAM
Note:
Typical values indicate operation at TA = 25°C, VCC = 5V or VBC = 3V.
13
bq3285E/L
DC Electrical Characteristics—bq3285L (TA = TOPR, VCC = 3.15V ± 0.45V)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
Conditions/Notes
ILI
Input leakage current
-
-
±1
µA
VIN = VSS to VCC
ILO
Output leakage current
-
-
±1
µA
AD0–AD7 and INT in high
impedance,
VOUT = VSS to VCC
VOH
Output high voltage
2.2
-
-
V
IOH = -1.0 mA
VOL
Output low voltage
-
-
0.4
V
IOL = 2.0 mA
ICC
Operating supply current
-
5
9
mA
Min. cycle, duty = 100%, IOH
= 0mA, IOL = 0mA
ICCSB
Standby supply current
-
100
-
µA
VIN = VSS or VCC,
CS ≥ VCC - 0.2
-
VPFD
-
V
VBC > VPFD
VSO
Supply switch-over voltage
-
VBC
-
V
VBC < VPFD
VBC = 3V, TA = 25°C,
VCC < VBC
ICCB
Battery operation current
-
0.3
0.5
µA
VPFD
Power-fail-detect voltage
2.4
2.53
2.65
V
IRCL
Input current when RCL = VSS.
-
-
120
µA
Internal 30K pull-up
Input current when MOT = VCC
-
-
-120
µA
Internal 30K pull-down
Input current when MOT = VSS
-
-
0
µA
Internal 30K pull-down
Input current when EXTRAM =
VCC
-
-
-120
µA
Internal 30K pull-down
Input current when EXTRAM =
VSS
-
-
0
µA
Internal 30K pull-down
IMOTH
IXTRAM
Note:
Typical values indicate operation at TA = 25°C, VCC = 3V.
14
bq3285E/L
Capacitance—bq3285E/L (TA = 25°C, F = 1MHz, VCC = 5.0V)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
Conditions
CI/O
Input/output capacitance
-
-
7
pF
VOUT = 0V
CIN
Input capacitance
-
-
5
pF
VIN = 0V
Note:
This parameter is sampled and not 100% tested. It does not include the X1 or X2 pin.
AC Test Conditions—bq3285E
Parameter
Test Conditions
Input pulse levels
0 to 3.0 V
Input rise and fall times
5 ns
Input and output timing reference levels
1.5 V (unless otherwise specified)
Output load (including scope and jig)
See Figures 4 and 5
Figure 4. Output Load A—bq3285E
Figure 5. Output Load B—bq3285E
15
bq3285E/L
AC Test Conditions—bq3285L
Parameter
Test Conditions
Input pulse levels
0 to 2.3 V
Input rise and fall times
5 ns
Input and output timing reference levels
1.2 V (unless otherwise specified)
Output load (including scope and jig)
See Figures 6 and 7
Figure 6. Output Load A—bq3285L
Figure 7. Output Load B—bq3285L
16
bq3285E/L
Read/Write Timing—bq3285E (TA = TOPR, VCC = 5V ± 10%)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
tCYC
Cycle time
160
-
-
ns
tDSL
DS low or RD/WR high time
80
-
-
ns
tDSH
DS high or RD/WR low time
55
-
-
ns
tRWH
R/W hold time
0
-
-
ns
tRWS
R/W setup time
10
-
-
ns
tCS
Chip select setup time
5
-
-
ns
tCH
Chip select hold time
0
-
-
ns
tDHR
Read data hold time
0
-
25
ns
tDHW
Write data hold time
0
-
-
ns
tAS
Address setup time
20
-
-
ns
tAH
Address hold time
5
-
-
ns
tDAS
Delay time, DS to AS rise
10
-
-
ns
tASW
Pulse width, AS high
30
-
-
ns
tASD
Delay time, AS to DS rise (RD/WR
fall)
35
-
-
ns
tOD
Output data delay time from DS rise
(RD fall)
-
-
50
ns
tDW
Write data setup time
30
-
-
ns
tBUC
Delay time before update cycle
-
244
-
µs
tPI
Periodic interrupt time interval
-
-
-
-
tUC
Time of update cycle
-
1
-
µs
17
Notes
See Table 3
bq3285E/L
Read/Write Timing—bq3285L (TA = TOPR, VCC = 3.15V ± 0.45V)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
tCYC
Cycle time
270
-
-
ns
tDSL
DS low or RD/WR high time
135
-
-
ns
tDSH
DS high or RD/WR low time
90
-
-
ns
tRWH
R/W hold time
0
-
-
ns
tRWS
R/W setup time
15
-
-
ns
tCS
Chip select setup time
8
-
-
ns
tCH
Chip select hold time
0
-
-
ns
tDHR
Read data hold time
0
-
40
ns
tDHW
Write data hold time
0
-
-
ns
tAS
Address setup time
30
-
-
ns
tAH
Address hold time
15
-
-
ns
tDAS
Delay time, DS to AS rise
15
-
-
ns
tASW
Pulse width, AS high
50
-
-
ns
tASD
Delay time, AS to DS rise (RD/WR
fall)
55
-
-
ns
tOD
Output data delay time from DS rise
(RD fall)
-
-
100
ns
tDW
Write data setup time
50
-
-
ns
tBUC
Delay time before update cycle
-
244
-
µs
tPI
Periodic interrupt time interval
-
-
-
-
tUC
Time of update cycle
-
1
-
µs
18
Notes
See Table 3
bq3285E/L
Motorola Bus Read/Write Timing—bq3285E/L
19
bq3285E/L
Intel Bus Read Timing—bq3285E/L
Intel Bus Write Timing—bq3285E/L
20
bq3285E/L
Power-Down/Power-Up Timing—bq3285E (TA = TOPR)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
tF
VCC slew from 4.5V to 0V
300
-
-
µs
tR
VCC slew from 0V to 4.5V
100
-
-
µs
tCSR
CS at VIH after power-up
20
-
200
ms
Conditions
Internal write-protection
period after VCC passes VPFD
on power-up.
Caution: Negative undershoots below the absolute maximum rating of -0.3V in battery-backup mode
may affect data integrity.
Power-Down/Power-Up Timing—bq3285E
21
bq3285E/L
Power-Down/Power-Up Timing—bq3285L (TA = TOPR)
Symbol
Parameter
Minimum
Typical
Maximum
Unit
tF
VCC slew from 2.7V to 0V
300
-
-
µs
tR
VCC slew from 0V to 2.7V
100
-
-
µs
tCSR
CS at VIH after power-up
20
-
200
ms
Conditions
Internal write-protection
period after VCC passes VPFD
on power-up.
Caution: Negative undershoots below the absolute maximum rating of -0.3V in battery-backup mode
may affect data integrity.
Power-Down/Power-Up Timing—bq3285L
22
bq3285E/L
Interrupt Delay Timing—bq3285E/L (TA = TOPR)
Minimum
Typical
Maximum
tRSW
Symbol
Reset pulse width
Parameter
5
-
-
µs
tIRR
INT release from RST
-
-
2
µs
tIRD
INT release from DS
-
-
2
µs
Interrupt Delay Timing—bq3285E/L
23
Unit
bq3285E/L
24-Pin DIP (P)
24-Pin DIP (0.600" DIP)
Inches
Millimeters
Dimension
Min.
Max.
Min.
Max.
A
0.160
0.190
4.06
4.83
A1
0.015
0.040
0.38
1.02
B
0.015
0.022
0.38
0.56
B1
0.045
0.065
1.14
1.65
C
0.008
0.013
0.20
0.33
D
1.240
1.280
31.50
32.51
E
0.600
0.625
15.24
15.88
E1
0.530
0.570
13.46
14.48
e
0.600
0.670
15.24
17.02
G
0.090
0.110
2.29
2.79
L
0.115
0.150
2.92
3.81
S
0.070
0.090
1.78
2.29
24-Pin SOIC (S)
24-Pin S (0.300" SOIC)
Inches
B
e
D
E
Millimeters
Dimension
Min.
Max.
Min.
Max.
A
0.095
0.105
2.41
2.67
A1
0.004
0.012
0.10
0.30
B
0.013
0.020
0.33
0.51
C
0.008
0.013
0.20
0.33
D
0.600
0.615
15.24
15.62
E
0.290
0.305
7.37
7.75
e
0.045
0.055
1.14
1.40
H
0.395
0.415
10.03
10.54
L
0.020
0.040
0.51
1.02
H
A
C
.004
A1
L
24
bq3285E/L
24-Pin SSOP (SS)
24-Pin SS (0.150" SSOP)
Inches
Dimension
Min.
Max.
Min.
Max.
A
0.061
0.068
1.55
1.73
A1
0.004
0.010
0.10
0.25
B
0.008
0.012
0.20
0.30
C
0.007
0.010
0.18
0.25
D
0.337
0.344
8.56
8.74
E
0.150
0.157
3.81
3.99
e
25
Millimeters
.025 BSC
0.64 BSC
H
0.230
0.244
5.84
6.20
L
0.016
0.035
0.41
0.89
bq3285E/L
Data Sheet Revision History
Change
No.
Page
No.
Description
Nature of Change
1
8
Register C, bit 2
Was 0; is na (not affected)
1
18
Output data delay time tOD
Was 80 ns max; is 100 ns max
2
1, 24, 26
Package option change
Lst time buy for some package options.
3
1, 24, 26
Package option change
Removed PLCC and added industrial SSOP package options
4
1, 11
Package option change
Industrial package option removed
Note:
Change 1 = Jan. 1995 B “Final” changes from Dec. 1993 A “Preliminary”.
Change 2 = Jan. 1999 C changes from Jan. 1995 B
Change 3 = Apr. 1999 D changes from Jan. 1999 C.
Change 4 = May 2004 (SLUS004A) changes from Apr. 1999 D
26
bq3285E/L
Ordering Information
bq3285E/L
Temperature:
blank = Commercial (0 to +70°C)
Package Option:
P = 24-pin plastic DIP (0.600)
S = 24-pin SOIC (0.300)
SS= 24-pin SSOP (0.150)
Device:
bq3285E Real-Time Clock with 242
bytes of general storage
or
bq3285L Real-Time Clock with 242
bytes of general storage
(3V operation)
bq3285L only available in 24-pin SSOP (0.150).
27
PACKAGE OPTION ADDENDUM
www.ti.com
18-Feb-2005
PACKAGING INFORMATION
Orderable Device
Status (1)
BQ3285EP
ACTIVE
PDIP
N
24
15
None
A42 SNPB
Level-NA-NA-NA
BQ3285ES
ACTIVE
SOIC
DW
24
25
None
CU SNPB
Level-1-220C-UNLIM
BQ3285ESS
ACTIVE
SSOP/
QSOP
DBQ
24
50
Pb-Free
(RoHS)
CU NIPDAU
Level-2-260C-1YEAR/
Level-1-220C-UNLIM
BQ3285ESSTR
ACTIVE
SSOP/
QSOP
DBQ
24
2500
Pb-Free
(RoHS)
CU NIPDAU
Level-2-260C-1YEAR/
Level-1-220C-UNLIM
2000
Level-1-220C-UNLIM
Package
Type
Package
Drawing
Pins Package Eco Plan (2)
Qty
Lead/Ball Finish
MSL Peak Temp (3)
BQ3285ESTR
ACTIVE
SOIC
DW
24
None
CU SNPB
BQ3285LSS
OBSOLETE
SSOP/
QSOP
DBQ
24
None
Call TI
Call TI
BQ3285LSSTR
OBSOLETE
SSOP
DB
24
None
Call TI
Call TI
(1)
The marketing status values are defined as follows:
ACTIVE: Product device recommended for new designs.
LIFEBUY: TI has announced that the device will be discontinued, and a lifetime-buy period is in effect.
NRND: Not recommended for new designs. Device is in production to support existing customers, but TI does not recommend using this part in
a new design.
PREVIEW: Device has been announced but is not in production. Samples may or may not be available.
OBSOLETE: TI has discontinued the production of the device.
(2)
Eco Plan - May not be currently available - please check http://www.ti.com/productcontent for the latest availability information and additional
product content details.
None: Not yet available Lead (Pb-Free).
Pb-Free (RoHS): TI's terms "Lead-Free" or "Pb-Free" mean semiconductor products that are compatible with the current RoHS requirements
for all 6 substances, including the requirement that lead not exceed 0.1% by weight in homogeneous materials. Where designed to be soldered
at high temperatures, TI Pb-Free products are suitable for use in specified lead-free processes.
Green (RoHS & no Sb/Br): TI defines "Green" to mean "Pb-Free" and in addition, uses package materials that do not contain halogens,
including bromine (Br) or antimony (Sb) above 0.1% of total product weight.
(3)
MSL, Peak Temp. -- The Moisture Sensitivity Level rating according to the JEDECindustry standard classifications, and peak solder
temperature.
Important Information and Disclaimer:The information provided on this page represents TI's knowledge and belief as of the date that it is
provided. TI bases its knowledge and belief on information provided by third parties, and makes no representation or warranty as to the
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incoming materials and chemicals. TI and TI suppliers consider certain information to be proprietary, and thus CAS numbers and other limited
information may not be available for release.
In no event shall TI's liability arising out of such information exceed the total purchase price of the TI part(s) at issue in this document sold by TI
to Customer on an annual basis.
Addendum-Page 1
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