ETC DS1632S

DS1632
PC Power-Fail and Reset Controller
www.dalsemi.com
FEATURES
•
•
•
•
•
•
•
•
•
•
•
•
PIN ASSIGNMENT
Power-fail detector for personal computers
and workstations
Connects directly to popular personal
computer chip sets
On chip 32.768 kHz oscillator for real time
clock
Provides battery backup power to clock chip
Pushbutton reset input
Accurate 5% or 10% +5-volt power supply
monitoring
Complementary outputs for reset, power-fail,
and low battery
Provides for reset pulse width of either 95 ms
or 190 ms
Eliminates the need for discrete components
Low-power CMOS circuitry
16-pin DIP or SOIC surface mount package
0°C to 70°C operation
PBRST
1
16
VCC
X1
2
15
PF
X2
3
14
PF
VBAT
4
13
VCCO
LB
5
12
RST
LB
6
11
RST
TOL
7
10
RD
GND
8
9
OSCOUT
16-Pin DIP (300-mil)
See Mech. Drawings Section
PBRST
1
16
VCC
X1
X2
2
3
15
14
PF
PF
VBAT
4
13
VCCO
LB
5
12
RST
RST
LB
6
11
TOL
7
10
GND
8
9
RD
OSCOUT
16-Pin SOIC (300-mil)
See Mech. Drawings Section
PIN DESCRIPTION
PBRST
X1, X2
VBAT
LB, LB
RST, RST
RD
TOL
GND
OSCOUT
VCCO
PF, PF
VCC
- Pushbutton Reset Input
- Crystal Inputs
- Battery Input
- Low Battery Outputs
- Reset Outputs
- Reset Duration
- Selects 5% Or 10% Detection
- Ground
- Oscillator Out
- Switched Power Out
- Power-Fail Outputs
- +5-Volt Power In
DESCRIPTION
The DS1632 PC Power-Fail and Reset Controller is designed to do various functions involving battery
backup and other functions typically accomplished with discrete components. The DS1632 provides a
32.768 kHz battery-backed crystal oscillator and switched VCC/VBAT power via VCCO for the real time
clock function located in accompanying chip sets. In addition, the DS1632 provides for reset on both
1 of 6
Powered by ICminer.com Electronic-Library Service CopyRight 2003
111999
DS1632
power-up and via pushbutton input, power-fail status signals for the processor, and low battery warning
signals. The DS1632 is capable of detecting power failure at both the 5% and 10% power supply
tolerances, and the reset pulse width can be set for either 95 ms or 190 ms. The device is designed to
connect directly to popular laptop and notebook chip sets which eliminates the need for discrete
components and reduces cost.
BLOCK DIAGRAM Figure 1
OPERATION - CRYSTAL OSCILLATOR SECTION
The DS1632 crystal oscillator is designed to be hooked directly to a 32.768 kHz crystal. By using the
Daiwa Part No. DT26S, Seiko Part No. DS-VT-200 or equivalent, the oscillator will be accurate enough
to run a real time clock to within ±2 minutes per month. If another crystal is to be selected, it should have
a specified load capacitance (CL) of 6 pF. The crystal oscillator will run as long as either VCC or VBAT is
present, providing that VBAT is greater than 2.3V. The oscillator output provides a rail to rail swing with
regards to VCC or VBAT, whichever is greater. The crystal oscillator is also used internally as a time base.
2 of 6
Powered by ICminer.com Electronic-Library Service CopyRight 2003
DS1632
OPERATION – POWER-FAIL, BATTERY BACKUP
The DS1632 provides a switch to direct power from the battery (VBAT) or the incoming supply (VCC),
depending on which is greater. This switch has a voltage drop of less than 0.2 volts. The VCC input is
constantly monitored by a precision comparator for an out-of-tolerance condition. When such a condition
occurs, the power-fail signals are driven to their active state immediately. The reset signals are also driven
active, but this action is delayed by a time determined by the level of the input on the reset duration pin
(RD). If RD is tied to ground then reset signals will become active after 9 ms. If RD is tied to VCC, then
reset signals will become active after 18 ms. Once active, both the reset signals and the power-fail signals
will remain active as long as a (VCC) out-of-tolerance condition persists. If an out-of-tolerance condition
is not long enough to activate the reset signals, then only the power-fail signals would be affected. When
power returns to within nominal limits the power-fail signals will return immediately to the inactive state.
However, the reset signals remain in the active state for a time which is dependent on the state of the RD
pin. If RD is tied to ground, the reset signals will remain active for 95 ms. If RD is tied to VCC, then the
reset signals will remain active for 190 ms after power is within nominal limits. The delay action on the
reset signals allows time for the power supply and microprocessor clock oscillators to stabilize. The
tolerance pin (TOL) selects the point at which power-fail detection occurs. With the tolerance pin
grounded, power-fail detection occurs in the range of 4.75V to 4.5V. If the tolerance pin is connected to
VCC, then power-fail detection occurs in the range of 4.5V to 4.25V. During most power supply
conditions the VCC input will supply power to all functions within the chip and also to the VCCO pin. The
battery pin (VBAT) only supplies power when VCC is less than VBAT. When VCC is below the level of VBAT
only the VCCO and the OSC OUT pin remain powered by VBAT. All other outputs will be driven to ground
when in a logic low state and will be driven to VCC when in a logic high state. This is done to preserve
battery capacity by avoiding battery drain resulting from loads on these outputs. The output ground level
will be maintained for all levels of VCC, even VCC = GND. However, the output VCC level will be
maintained only for VCC > 2.0V. Internal battery power consumption is less than 2 µA while VBAT is
supplying power. The external load on OSC OUT and VCCO must be added to internal consumption to
determine the total load on the battery.
OPERATION - PUSHBUTTON RESET
The DS1632 provides an input pin for direct connection to a pushbutton. The pushbutton reset input
PBRST requires an active low level input. While TTL levels are sufficient to properly activate this input,
it has been primarily designed for contact closure. Internally, this input is debounced and timed such that
RST and RST signals of 95ms or 190 ms minimum are generated. If RD is tied to ground, then a reset
pulse of 95 ms is generated. If RD is tied to VCC then a reset pulse of 190 ms is generated. The delay time
is started as the pushbutton reset input is released from low level.
OPERATION - LOW BATTERY WARNING
The DS1632 provides outputs which warn of a low battery condition. Whenever VCC is within nominal
limits, the VBAT input is continuously monitored. If the VBAT input is out of tolerance, the low battery
outputs are driven to their active states, and will remain in the active state as long as VCC is within
nominal limits or until the battery input is restored to an in limit status. On power-up, if the VBAT input is
out of tolerance, the low battery outputs are not guaranteed active until power-fail is deactivated, but
guaranteed active prior to reset inactive. When VCC is below the VCC fail trip point both LB and LB will
be driven to ground.
For application information, please reference Application Note 64, published separately.
3 of 6
Powered by ICminer.com Electronic-Library Service CopyRight 2003
DS1632
ABSOLUTE MAXIMUM RATINGS*
Voltage on VCC Pin Relative to Ground
Voltage on I/O Relative to Ground
Operating Temperature
Storage Temperature
Soldering Temperature
*
-0.5V to +7.0V
-0.5V to VCC + 0.5V
0°C to 70°C
-55°C to +125°C
260°C for 10 seconds
This is a stress rating only and functional operation of the device at these or any other conditions
above those indicated in the operation sections of this specification is not implied. Exposure to
absolute maximum rating conditions for extended periods of time may affect reliability.
RECOMMENDED DC OPERATING CONDITIONS
PARAMETER
Supply Voltage
SYMBOL
VCC
MIN
4.5
(0°C to 70°C)
TYP
5.0
MAX
5.5
UNITS
V
NOTES
1
PBRST
Input High Level
VIH
2.0
VCC+0.3
V
1, 3
PBRST
Input Low Level
VIL
-0.3
+0.8
V
1, 3
VBAT
2.3
3.5
V
1
Battery Supply Voltage
DC ELECTRICAL CHARACTERISTICS
PARAMETER
3.0
(0°C to 70°C; VCC=4.5 to 5.5V)
SYMBOL
MIN
Output Current @ 2.4V
IOH
Output Current @ 0.4V
IOL
Output Voltage @ -500 µA
VOH
Low Level @ RST
VOL
Operating Current
ICC
TYP
MAX
UNITS
NOTES
1
mA
5, 7
4
mA
7
V
1, 6
0.4
V
1
0.5
2.0
mA
2
VCC-0.5V VCC-0.1V
VCC Trip Point (TOL=GND)
VCCTP
4.50
4.62
4.75
V
1
VCC Trip Point (TOL=VCC)
VCCTP
4.25
4.37
4.50
V
1
Battery Fail Trip Point
VBATTP
2.30
2.45
2.55
V
1
Supply Voltage Output
VCCO
VCC-0.2
Supply Current Output
ICCO1
V
100
DC ELECTRICAL CHARACTERISTICS
PARAMETER
SYMBOL
Battery Current
Battery Backup Current
mA
(0°C; VCC=<VBAT)
MIN
TYP
MAX
UNITS
IBAT
2
µA
ICCO2
500
µA
CAPACITANCE
PARAMETER
Input Capacitance
Output Capacitance
4
NOTES
4
(tA=25°C)
SYMBOL
CIN
MIN
COUT
4 of 6
Powered by ICminer.com Electronic-Library Service CopyRight 2003
TYP
MAX
5
UNITS
pF
7
pF
NOTES
DS1632
AC ELECTRICAL CHARACTERISTICS
PARAMETER
(0°C to 70°C; VCC=5V ± 10%)
SYMBOL
tPB
MIN
tRPD
MAX
UNITS
ms
NOTES
Reset Pulse Width
tRST
95
105
ms
RD=GND
Reset Pulse Width
tRST
190
210
ms
RD=VCC
Reset Active on Power-Up
tRPU
95
105
ms
RD=GND
Reset Active on Power-Up
tRPU
190
210
ms
RD=VCC
Reset Active on Power-Down
tRPD
9
11
ms
RD=GND
Reset Active on Power-Down
tRPD
18
22
ms
RD=VCC
VCC Slew Rate Power-Down
tF
300
µs
VCC Slew Rate Power-Down
tFB
10
µs
VCC Slew Rate Power-Up
tR
10
µs
PBRST
= VIL
TIMING DIAGRAM: PUSHBUTTON RESET
TIMING DIAGRAM: POWER-DOWN
5 of 6
Powered by ICminer.com Electronic-Library Service CopyRight 2003
TYP
DS1632
TIMING DIAGRAM: POWER-UP
NOTES:
1. All voltages are referenced to ground.
2. Measured with outputs open.
3. The PBRST input has an internal pull-up of 10kΩ=to VCC.
4. Supply current output is specified with 0.2V drop from VBAT or VCC.
5. RST , PF , and LB are open-drain outputs.
6. RST and PF remain within 0.5 volts of VCC on power down until VCC drops below 2.0V.
7. Sink and source currents apply to all outputs except OSC OUT which has a drive capability of
sourcing 500 µA at VOH = VCCO - 0.5V and sinking 1 mA at VOL = 0.5 V.
6 of 6
Powered by ICminer.com Electronic-Library Service CopyRight 2003