LTC2956 - Wake-Up Timer with Pushbutton Control

LTC2956
Wake-Up Timer with
Pushbutton Control
FEATURES
DESCRIPTION
1.5V to 36V Supply Input Range
nn Adjustable Wake-Up Period: 250ms to 39 Days
nn Adjustable Maximum Awake Time
nn 0.8µA Quiescent Current
nn 0.3µA Shutdown Current
nn Pushbutton Input with Debouncing
nn Low Leakage EN Output Allows DC/DC Converter
Control (LTC2956-1)
nn High Voltage EN Output Drives External P-Channel
MOSFET (LTC2956-2)
nn ±25kV ESD HBM on PB Input
nn 12-Lead 3mm × 3mm QFN and MSOP Packages
The LTC®2956 is a micropower, wide input voltage range,
configurable wake-up timer with pushbutton control. It
periodically wakes up and turns on a connected system
to perform tasks like monitoring temperature or capturing
images. After completing the task, the LTC2956 turns the
system off to conserve power.
nn
The wake-up timer period can be adjusted from 250ms to
39 days using configuration resistors. The system awake
time can be controlled by the input pulse at the SLEEP
pin or adjusted by the capacitor at the ONMAX pin. The
LTC2956 operates over a wide supply input range from
1.5V to 36V. The low 800nA quiescent current suits battery powered applications.
APPLICATIONS
The pushbutton input allows the user to shutdown, turn
on or reset the wake-up timer. With the timer in shutdown,
the quiescent current drops to 300nA. The LTC2956 also
provides three status outputs to indicate mode transitions
and pushbutton events. Two versions are available for
applications requiring either positive or negative enable
polarities.
Heartbeat Timers
Periodic Wake-Up Control
nn Portable and Battery-Powered Equipment
nn Intervalometers
nn Data Acquisition
nn
nn
L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks and
PowerPath and ThinSOT are trademarks of Linear Technology Corporation. All other trademarks
are the property of their respective owners.
TYPICAL APPLICATION
+
VBAT
VIN
1µF
LT3060
VOUT
SHDN
VMAIN
10k
VIN
1.5nF
EN
10k
280k
100k
LONG PRESS STOPS
CYCLING TIMER
PB
10k
ONMAX LTC2956-1 PBOUT
TURNED ON
ONALERT
TURNING OFF
OFFALERT
PB
SLEEP
GND
LONG RANGE
SHORT PRESS STARTS
CYCLING TIMER
µP SHUTS OFF
POWER
SLEEP
µP
PERIOD
TIMER PERIODICALLY
ENABLES POWER
EN
100k
tAWAKE
9.76k
tLONG = 1s, tONMAX = 20ms, tPERIOD = 250ms
tSLEEP
tPERIOD
2956 TA01b
2956 TA01a
2956fa
For more information www.linear.com/LTC2956
1
LTC2956
ABSOLUTE MAXIMUM RATINGS
(Note 1)
VIN (Note 3)................................................. –0.3V to 40V
Input Voltages:
PB............................................................ –40V to 40V
SLEEP....................................................... –0.3V to 6V
LONG, PERIOD, RANGE, ONMAX.............0.3V to 3.6V
Output Voltages:
ONALERT, PBOUT, OFFALERT.................... –0.3V to 6V
EN/EN..................................................... –0.3V to 40V
Operating Temperature Range:
LTC2956C................................................. 0°C to 70°C
LTC2956I..............................................–40°C to 85°C
Storage Temperature Range:
QFN Package...................................... –65°C to 150°C
MSOP Package................................... –65°C to 150°C
Lead Temperature (Soldering, 10 sec):
MSOP Package.................................................. 300°C
PIN CONFIGURATION
PBOUT
OFFALERT
SLEEP
TOP VIEW
TOP VIEW
12 11 10
ONALERT 1
13
GND
RANGE
4
5
*EN/EN
8
PB
7
GND
ONMAX
LONG
RANGE
PERIOD
VIN
GND
6
VIN
LONG 3
PERIOD
ONMAX 2
9
UD PACKAGE
12-LEAD (3mm × 3mm) PLASTIC QFN
TJMAX = 125°C, θJA = ~68°C/W
EXPOSED PAD (PIN 13) IS GND, PCB CONNECTION OPTIONAL
*PIN 9 IS EN FOR LTC2956-1 AND IS EN FOR LTC2956-2
1
2
3
4
5
6
12
11
10
9
8
7
ONALERT
SLEEP
OFFALERT
PBOUT
*EN/EN
PB
MS PACKAGE
12-LEAD PLASTIC MSOP
TJMAX = 125°C, θJA = 135°C/W
*PIN 8 IS EN FOR LTC2956-1 AND IS EN FOR LTC2956-2
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2956CUD-1#PBF
LTC2956CUD-1#TRPBF
LGNH
12-Lead (3mm × 3mm) Plastic QFN
0°C to 70°C
LTC2956CUD-2#PBF
LTC2956CUD-2#TRPBF
LGTC
12-Lead (3mm × 3mm) Plastic QFN
0°C to 70°C
LTC2956IUD-1#PBF
LTC2956IUD-1#TRPBF
LGNH
12-Lead (3mm × 3mm) Plastic QFN
–40°C to 85°C
LTC2956IUD-2#PBF
LTC2956IUD-2#TRPBF
LGTC
12-Lead (3mm × 3mm) Plastic QFN
–40°C to 85°C
LTC2956CMS-1#PBF
LTC2956CMS-1#TRPBF
29561
12-Lead Plastic MSOP
0°C to 70°C
LTC2956CMS-2#PBF
LTC2956CMS-2#TRPBF
29562
12-Lead Plastic MSOP
0°C to 70°C
LTC2956IMS-1#PBF
LTC2956IMS-1#TRPBF
29561
12-Lead Plastic MSOP
–40°C to 85°C
LTC2956IMS-2#PBF
LTC2956IMS-2#TRPBF
29562
12-Lead Plastic MSOP
–40°C to 85°C
Consult LTC Marketing for parts specified with wider operating temperature ranges. *The temperature grade is identified by a label on the shipping container.
Consult LTC Marketing for information on nonstandard lead based finish parts.
For more information on lead free part marking, go to: http://www.linear.com/leadfree/
For more information on tape and reel specifications, go to: http://www.linear.com/tapeandreel/
2
2956fa
For more information www.linear.com/LTC2956
LTC2956
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.3V, RCOM = 100k unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
VIN
Supply Voltage Range
CONDITIONS
MIN
IIN
VIN Supply Current
Awake State, PB Hi
Sleep State, PB Hi
Off State, PB Hi
l
l
l
VUVL
VIN Undervoltage Lockout
VIN Rising
l
VUVL(HYST)
VIN Undervoltage Lockout Hysteresis
l
TYP
1.5
1.08
MAX
UNITS
36
V
3
0.8
0.3
10
3
1
µA
µA
µA
1.24
1.4
V
100
mV
Wake-Up Timer
tPERIOD
Period Accuracy
RPERIOD
Period-Setting Resistor Range
RPERIOD = 100kΩ
l
237
l
32.4
250
263
ms
324
kΩ
Timing (Refer to Timing Diagram)
tSLEEP_MIN
Minimum Sleep Duration
l
76
128
180
ms
tAWAKE_MIN
Minimum Awake Time
l
4
8
12
ms
tONMAX
Maximum Awake Time
SLEEP = 0V, CONMAX = 3900pF
l
32
52
72
ms
tDB
PB Debounce Time
PB Goes Low → EN Goes High
l
19
32
45
ms
tPD(SLEEP)
SLEEP Propagation Delay
SLEEP → EN Transitions
l
2
4
ms
tPBOUT_FIRST
Width of First PBOUT Pulse After Entering Awake State
l
76
128
180
ms
tLONG
Long Power Down Time
RLONG = 9.76k, RCOM = 100k
RLONG = Open, RCOM = 100k
l
l
76
9.83
128
16.4
180
22.9
ms
s
tOFF
OFFALERT Pulse Width
PB = 2V
l
0.6
1
1.4
s
l
–36
36
V
Input Pins: PB, ONMAX, SLEEP
VPB(MIN,MAX)
PB Voltage Range
IPB
PB Input Current
PB = 0V
PB = –36V
l
–1
–4
–8
–400
µA
µA
VPB(TH)
PB Input Threshold
PB Falling
l
0.5
0.9
1.5
V
IPB = 0µA, –1µA
l
1.5
l
0.45
0.9
1.35
MΩ
l
0.7
1
1.3
V
VPB(HYST)
PB Input Hysteresis
VPB(OC)
PB Open Circuit Voltage
0.7
V
V
RPB
PB Pull-Up Resistance
VSLEEP(TH)
SLEEP Input Threshold Voltage
VSLEEP(HYST)
SLEEP Input Hysteresis
ISLEEP
SLEEP Leakage Current
SLEEP = 1V
l
0
±100
nA
VONMAX(TH)
ONMAX Input Threshold Voltage
ONMAX Rising
l
0.6
1
1.5
V
IONMAX
ONMAX Pull-Up Current
ONMAX = 0V
l
–1.1
–2
–2.8
µA
SLEEP Falling
80
mV
2956fa
For more information www.linear.com/LTC2956
3
LTC2956
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VIN = 3.3V, RCOM = 100k unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Output Pins: EN/EN, PBOUT, ONALERT, OFFALERT, PERIOD, RANGE, LONG
VEN(VOH)
EN Voltage Output High (LTC2956-1)
I = 0µA, –1µA
l
1.5
VEN(VOH)
EN Voltage Output High (LTC2956-2)
I = 0µA, –1µA
l
V
VIN – 1.5
REN/EN
EN/EN Pull-Up Resistance
l
0.45
VOL
Output Low Voltage (EN/EN)
Output Low Voltage (ONALERT, PBOUT)
Output Low Voltage (OFFALERT)
I = 1mA
I = 3mA
I = 6mA
IOH
Input Leakage Current (RANGE, LONG)
Leakage Current (PBOUT, ONALERT, OFFALERT)
VPERIOD
PERIOD Open Circuit Voltage
VIN
V
1.35
MΩ
l
l
l
0.4
0.4
0.4
V
V
V
V = 1.5V
V = 5V
l
l
±100
±100
nA
nA
I = –1µA
l
0.5
V
Note 1: Stresses beyond those listed under Absolute Maximum Ratings
may cause permanent damage to the device. Exposure to any Absolute
Maximum Rating condition for extended periods may affect device
reliability and lifetime.
Note 2: All currents into device pins are positive; all currents out of device
pins are negative; all voltages are referenced to GND unless otherwise
noted.
0.9
0.3
0.4
Note 3: A substrate diode limits the VIN pin to a minimum of –0.3V with
respect to GND. This pin may go below –0.3V with current limited to less
than 50mA.
tDB
tDB
PB
PBOUT
tLONG
tPBOUT_FIRST
tPD(SLEEP)
tPD(SLEEP)
SLEEP
tAWAKE_MIN
EN
tSLEEP_MIN
tPERIOD
tSLEEP_MIN
tONMAX
tOFF
OFFALERT
ONALERT
2956 EC TD
Timing Diagram
4
2956fa
For more information www.linear.com/LTC2956
LTC2956
TYPICAL PERFORMANCE CHARACTERISTICS
Supply Current vs Temperature
1.4
1.30
SLEEP STATE
1.75
1.25
IVIN (µA)
IVIN (µA)
TA = 85°C
1.2
1.50
SLEEP STATE
0.75
0.50
0
–50
–25
0
50
25
TEMPERATURE (°C)
1.0
TA = 25°C
0.8
TA = –40°C
0.6
OFF STATE
0.25
1.28
VUVL (V)
2.00
1.00
Undervoltage Lockout vs
Temperature
Supply Current vs Supply Voltage
75
0.4
100
1.24
1.22
0
5
10
15
2956 G01
Wake-Up Period vs PERIOD
Resistance
1.26
20 25
VIN (V)
30
35
1.20
–50
40
NRANGE = 4
3.5 RCOM = 100k
RRANGE = 17.4k
75
100
2956 G03
10000
NRANGE = 1
RPERIOD = 100k
254
25
0
50
TEMPERATURE (°C)
2956 G02
Wake-Up Period vs Temperature
256
4.0
–25
Maximum Awake Time vs CONMAX
2.0
1.5
252
tONMAX (ms)
2.5
tPERIOD (ms)
tPERIOD (seconds)
3.0
250
248
1000
100
1.0
246
0.5
0
0
50
244
–50
100 150 200 250 300 350 400
RPERIOD (kΩ)
–25
0
50
25
TEMPERATURE (°C)
75
2956 G04
EN Output High Voltage vs
Supply Voltage
65
4.0
3.5
3.0
VEN(VOH) (V)
VEN(VOH) (V)
tONMAX (ms)
45
2.5
2.0
40
30
–50
–25
0
50
25
TEMPERATURE (°C)
75
100
2956 G07
1.0
1000
2956 G06
VIN = 7V
3.6
3.4
3.2
1.5
35
100
CONMAX (nF)
3.8
60
50
10
EN Output High Voltage vs
Temperature
4.0
CONMAX = 3.9nF
55
1
2956 G05
Maximum Awake Time vs
Temperature
70
10
100
1
2
3
4
VIN (V)
5
6
7
2956 G08
3.0
–50
–25
25
0
50
TEMPERATURE (°C)
75
100
2956 G09
2956fa
For more information www.linear.com/LTC2956
5
LTC2956
TYPICAL PERFORMANCE CHARACTERISTICS
EN/EN Output Low Voltage vs
Temperature
0.4
IEN = 1mA
0.2
0.1
50
VIN = 3.3V
TA = 25°C
45
TA = 85°C
0.3
VEN/EN(VOL) (V)
VEN/EN(VOL) (V)
0.3
PB Debounce Time vs
Temperature
TA = –40°C
40
tDB (ms)
0.4
EN/EN Output Low Voltage vs
Current
0.2
35
30
0.1
25
0
–50
–25
25
0
50
TEMPERATURE (°C)
75
0
0.0
100
2956 G10
0.5
1.0
1.5
2.0
IEN/EN (mA)
2.5
20
–50
3.0
–200
300
–160
250
–120
200
0
50
25
TEMPERATURE (°C)
ONALERT Output Low Voltage vs
Current
0.4
VIN = 3.3V
0
40
–40
TA = 85°C
TA = –40°C
0.2
TA = –40°C
0.1
50
–20
0
20
PB VOLTAGE (V)
40
2956 G13
6
150
100
TA = 25°C
TA = 85°C
TA = 25°C
VVOL (V)
PB VOLTAGE (mV)
IPB (µA)
–40
100
2956 G12
0.3
–80
75
2956 G11
PB Voltage vs External PB
Resistance to Ground
PB Input Current vs PB Voltage
–25
0
10
30
0
20
40
50
EXTERNAL PB RESISTANCE TO GROUND (kΩ)
2956 G14
0
0
2
4
8
6
10
IOFFALERT (mA)
12
14
16
2956 G15
2956fa
For more information www.linear.com/LTC2956
LTC2956
PIN FUNCTIONS
EN: Enable Output (LTC2956-1). EN is an active high output
to control the turn-on/off of a load. Connect this pin to
the RUN or SHUTDOWN pin of a voltage regulator. The
LTC2956-1 pulls EN high through an internal 900k resistor and Schottky diode to a 3.3V regulated supply when
the pushbutton is pressed or when the wake-up period
is reached. EN pulls low during the Sleep state. This pin
may be left open if unused.
EN: Inverted Enable Output (LTC2956-2). EN is an active
low output to control the turn-on/off of the system power.
It may drive a voltage regulator’s active low enable input,
or it may drive the gate of a P-channel MOSFET directly.
In the Sleep state, the LTC2956-2 pulls this pin to VIN
through an internal 900k resistor. The LTC2956-2 pulls
EN to GND when the pushbutton is pressed or when the
wake-up timer period is reached. This pin may be left
open if unused.
Exposed Pad (QFN only): Exposed Pad. Leave open or
connect to device ground.
GND: Device Ground.
LONG: Long Power Down Time Selection Input. Connect a
resistor from the LONG pin to GND. Together with the 100k
resistor between the RANGE and LONG pin, this adjusts
the tLONG power down time (tLONG can be adjusted from
128ms to 16.4s). If SLEEP is pulled high or PB is pulled
low longer than tLONG, the part goes into SHUTDOWN
mode. See Applications Information for details.
OFFALERT: Off Alert Open Drain Output. The LTC2956
pulls this pin low for 1 second (tOFF) whenever the part
goes from RUN mode to SHUTDOWN mode. This pin can
be connected to the interrupt input of the system (with a
pull-up resistor to the system supply) to alert the system
before shutdown. It can also be used to drive an external
LED to give a visual indication. This pin may be left open
if unused.
ONALERT: On Alert Open Drain Output. The LTC2956 pulls
this pin low whenever the part goes from SHUTDOWN
mode to RUN mode. The pin stays low while the EN pin
is high and it can be used as an input to the system to
request for initial boot up routine. This pin may be left
open if unused.
ONMAX: Maximum Awake Timer Capacitor Input. Connect
a capacitor from this pin to GND adjust the maximum
allowed awake time (tONMAX) at 13.3ms/nF. If this pin is
left floating, the minimum awake time is limited to 8ms.
Tie this pin to GND if unused.
PB: Pushbutton Input. This is an active low input with a
900kΩ pull-up to an internal 3.3V regulated supply. Connect one terminal of the pushbutton switch to this pin and
connect the other terminal of a pushbutton switch to GND.
The pin may be left open if unused.
PBOUT: Debounced Pushbutton Open Drain Output. This
pin follows the debounced PB input. This pin may be left
open if unused.
PERIOD: Wake-Up Timer Adjust Input. Connect a resistor
from the PERIOD pin to GND to adjust the wake-up timer
period. See the Application Section for resistor selection
information.
RANGE: Wake-Up Timer Range Selection Input. Connect a
resistor from the RANGE pin to GND and a 100k resistor
between the RANGE and LONG pin to choose the wakeup timer period range setting. See Application Section for
information about the resistor selection.
SLEEP: SLEEP Input. The SLEEP input is active during
RUN mode. In the Awake state, a falling edge at the SLEEP
input will pull EN low (EN high) and put the system into
the Sleep state. If the SLEEP input goes high during the
Sleep state, the LTC2956 re-enters the Awake state and
pulls EN high (EN low) to turn on the system. Holding
SLEEP high for more than tLONG will force the system into
the SHUTDOWN mode. If unused, tie SLEEP to GND, and
use the ONMAX pin to control the awake time.
VIN: Power Supply Input (1.5V to 36V).
2956fa
For more information www.linear.com/LTC2956
7
LTC2956
BLOCK DIAGRAM
VIN
REGULATOR
VCC
VCC
M4
VCC
900k
EN (LTC2956-1)
900k
PB
–
CMP1
LOGIC
+
0.9V
M5
32ms
DEBOUNCE
VIN
M2
900k
SLEEP
–
EN (LTC2956-2)
CMP2
M3
+
1V
PBOUT
M6
OSC2
f = 1kHz
CLK
PROGRAMMABLE
DIVIDER
÷ 1, 4, …222
ONALERT
M7
OSC1
400kΩ
RPERIOD
OFFALERT
f = 2kHz •
M1
+
IPERIOD
M8
S3
0.4V
ONMAX
TIMER
AMP
ONMAX
–
PERIOD
VCC
VCC
S1
S2
LONG
RANGE
GND
2956 BD
RPERIOD
RLONG
8
RCOM
RRANGE
2956fa
For more information www.linear.com/LTC2956
LTC2956
OPERATION
OFF STATE:
EN = 0
OFFALERT = 1
ONALERT = 1
VLONG < VCC/2
tOFF = TRUE
SHUTTING OFF
STATE:
EN = 1
OFFALERT = 0
POWER-ON
VLONG > VCC/2
tSLEEP_MIN = TRUE AND
PB = LOW
SHUTDOWN MODE
FROM OFF STATE:
ONALERT = 0
EN = 1
(PB = LOW FOR tLONG)
OR (tONMAX = FALSE AND
SLEEP = HIGH FOR tLONG)
AWAKE STATE:
EN = 1
tPERIOD RESTART
PB = HIGH AND
tAWAKE_MIN = TRUE AND
(SLEEP↓ = TRUE OR
tONMAX = TRUE)
tSLEEP_MIN = TRUE AND
(tPERIOD = TRUE OR
PB = LOW OR
SLEEP = HIGH)
SLEEP STATE:
EN = 0
ONALERT = 1
OFFALERT = 1
RUN MODE
2956 F01
Figure 1. Functional State Diagram
2956fa
For more information www.linear.com/LTC2956
9
LTC2956
OPERATION
OVERVIEW
The LTC2956 is a micropower, highly configurable wake-up
timer with pushbutton control. It controls power to a connected system to allow that system to perform a periodic
task. After completing the task, the LTC2956 turns the
system off to conserve power. Figure 1 shows a simplified state diagram of the LTC2956. The LTC2956 has two
modes of operation: RUN mode and SHUTDOWN mode.
In RUN mode, the LTC2956 cycles between the Awake
state and the Sleep state with a period of tPERIOD. During
the Awake state the EN pin is pulled high to turn the system on, and the tONMAX timer runs. The LTC2956 exits the
Awake state when a falling edge is detected on the SLEEP
pin or if the tONMAX timer expires. The LTC2956 ignores
any SLEEP pin transitions for tAWAKE_MIN (typically 8ms)
after entering the Awake state to ensure that the minimum
on time is met.
In the Sleep state, the EN output stays low, and the connected system turns off. The LTC2956 returns to the Awake
state if the tPERIOD time is reached, if the pushbutton
(connected to the PB pin) is pressed, or if a logic high
is detected on the SLEEP pin. The minimum duration for
the Sleep state is tSLEEP_MIN (typically 128ms), and any
input or tPERIOD transitions during this time are ignored in
order to allow the system supply to sufficiently discharge.
SHUTDOWN mode is a very low power mode with the timer
disabled, entered through a long press of the pushbutton
or a long high pulse at the SLEEP input. This is useful for
products that are shipped with their batteries installed. A
short press on the pushbutton brings the LTC2956 back
into RUN mode. The LTC2956 can be configured to start
in either RUN or SHUTDOWN mode at power-up via the
LONG pin (see the Applications Information section).
SHUTDOWN mode consists of the Shutting Off state and
the Off state. The Shutting Off state occurs first during
the transition from RUN mode to SHUTDOWN mode, and
allows time for the system to perform any shutdown tasks
before the EN pin goes low in the Off state. This state is
indicated by the OFFALERT pin pulling low and lasts for
10
tOFF (typically 1s). Once the tOFF timer completes, the
LTC2956 transitions to the Off state, the EN pin is pulled
low and all timers are disabled, and the quiescent current
drops to about 0.3μA.
When the LTC2956 returns to the RUN mode from the
SHUTDOWN mode, it first enters the From Off state to
allow the connected system to run initialization tasks. This
is indicated by the ONALERT pin pulling low. The EN pin
is pulled high to turn the connected system on.
The LTC2956 turns the connected system on and off
via the EN pin. The LTC2956-1's active high EN pin can
be connected to the system supply RUN pin while the
LTC2956-2's active low EN pin can directly control the
system supply through a P-channel MOSFET.
The wake-up timer period can be adjusted from 250ms to
39 days via resistors at the PERIOD and RANGE pins. The
timing of the long pushbutton press and SLEEP pulse can
be adjusted via resistors connected to the LONG pin. To
minimize the quiescent current, the RANGE, LONG, and
PERIOD pins are biased only when the LTC2956 performs
a configuration cycle.
Timer configuration is performed once every 66 seconds
while the part is operating in RUN mode, and it is also
performed following power-up and whenever the LTC2956
exits the SHUTDOWN mode. During configuration, the
LTC2956 biases and reads the voltages at the RANGE
and LONG pins that are defined by external configuration
resistors. See Configuration section for more details.
Operations with SLEEP Tied Low (Passive System)
The LTC2956 is designed to control the power of both
active and passive systems. With a passive system where
the SLEEP pin is not managed by a microcontroller, the
SLEEP pin can be tied low and a capacitor connected to
the ONMAX pin determines the awake time. The minimum
tONMAX must be longer than the maximum expected time
the system takes to complete its routine tasks.
2956fa
For more information www.linear.com/LTC2956
LTC2956
OPERATION
Figure 2 shows the timing waveform of a passive system
application using a LTC2956-1. When the tPERIOD time is
reached, the LTC2956 enters the Awake state and pulls the
EN output high to turn on the system. The tPERIOD timer
restarts and the tONMAX timer starts running. Once the
tONMAX timer expires, the LTC2956 re-enters the Sleep state
and pulls the EN output low. The tPERIOD timer continues
to run until the next period is reached.
Note that the tPERIOD timer is a digital counter inside the
LTC2956, but it is illustrated as a simple ramp in all the
figures in this data sheet. The tONMAX timer counts using
both the analog ramp on the ONMAX pin as well as an
internal digital counter. It is also represented as a simple
ramp in all the figures in this data sheet.
The LTC2956 ignores the tONMAX timer during the first 8ms
(tAWAKE_MIN) after the EN output is pulled high which limits
the minimum tAWAKE time to tAWAKE_MIN (8ms typical).
Operations with SLEEP Toggling (Active System)
With an active system, i.e. microprocessor based, the
system can toggle the SLEEP pin to terminate the Awake
state immediately after it has completed a routine/periodic
task. The LTC2956 will pull the EN output low to turn off
the system and enter the Sleep state. This keeps the awake
time to a minimum and helps minimize the drain on the
system battery.
Figure 3 shows the timing waveform for an active system application. When the tPERIOD time is reached, the
LTC2956-1 enters the Awake state and pulls the EN output
high to turn on the system. The tPERIOD timer resets, and
the tONMAX timer start running. When the system has
completed its periodic task, the LTC2956 is commanded
to re-enter the Sleep state by pulling the SLEEP pin low.
The LTC2956 ignores both the SLEEP pin and tONMAX
timer during the tAWAKE_MIN interval (8ms typical) just
after EN goes high in order to guarantee that the system
has stabilized. If the system completes its task before
tAWAKE_MIN is reached, it can toggle SLEEP continuously
until the LTC2956 responds by pulling EN low (Figure 4). If
the system only toggles the SLEEP pin during tAWAKE_MIN,
the LTC2956 will not respond to the SLEEP pin’s falling
edge(s) and remains in the Awake state until the tONMAX
timer expires.
If SLEEP is held low during the entire Awake state period, the tONMAX timer will timeout (Figure 2) forcing the
tPERIOD
TONMAX
tONMAX
EN
SLEEP
IGNORED
IGNORED
OV
tAWAKE_MIN
tAWAKE_MIN
tPERIOD TIMER
STATE
SLEEP
AWAKE
SLEEP
AWAKE
2956 F02
Figure 2. Operation with SLEEP Tied Low (Passive System)
2956fa
For more information www.linear.com/LTC2956
11
LTC2956
OPERATION
tPERIOD
TONMAX
tONMAX
EN
IGNORED
IGNORED
SLEEP
tAWAKE_MIN
tAWAKE_MIN
tPERIOD TIMER
STATE
SLEEP
AWAKE
SLEEP
AWAKE
2956 F03
Figure 3. Operation with SLEEP Toggling (Active System)
tPERIOD
TONMAX
tONMAX
EN
IGNORED
IGNORED
SLEEP
tAWAKE_MIN
tAWAKE_MIN
tPERIOD TIMER
STATE
SLEEP
SLEEP
AWAKE
AWAKE
2956 F04
Figure 4. Toggling SLEEP Continuously to Enter Sleep State
LTC2956-1 back into the Sleep state. This tONMAX watchdog
timer feature is particularly useful in applications where
an active system’s software/firmware might encounter
a stuck state or infinite loop thus preventing the system
from excessively discharging the battery.
Power Up
The LTC2956 can be configured to power up automatically
in either RUN or SHUTDOWN mode. This is done through
12
the resistive divider setting at LONG pin. If the voltage on
the LONG pin is configured to be greater than VCC /2 (see
Table 2), the LTC2956 enters the RUN mode (see Figure
5). If the voltage on the LONG pin is configured to be less
than VCC /2, the LTC2956 enters the SHUTDOWN mode. In
SHUTDOWN mode, a press of the push button is needed
to transition the wake-up timer to the Awake state and
start the tPERIOD timer (Figure 6). tCONFIGURATION is the
system configuration time. It can last between 0.1s to 1s.
2956fa
For more information www.linear.com/LTC2956
LTC2956
OPERATION
VIN
PB
PBOUT
ONALERT
tCONFIGURATION
tSLEEP_MIN
EN
SLEEP
tPERIOD
tPERIOD
tPERIOD TIMER
tPERIOD
STOP
TONMAX
STATE
OFF
AWAKE/FROM OFF
SLEEP AWAKE
SLEEP
AWAKE
SLEEP
2956 F05
Figure 5. Wake-Up Timer Goes into RUN Mode After Power-Up (VLONG > VCC/2)
VIN
PB
tDB
tCONFIGURATION
PBOUT
ONALERT
EN
SLEEP
tPERIOD
tPERIOD
tPERIOD TIMER
STOP
TONMAX
STATE
OFF
AWAKE/FROM OFF
SLEEP AWAKE
SLEEP
AWAKE
2956 F06
Figure 6. Using the PB to Start the Wake-Up Timer
2956fa
For more information www.linear.com/LTC2956
13
LTC2956
OPERATION
The ONALERT open drain output is pulled low on the first
Awake state after exiting SHUTDOWN mode or when first
powered up with VLONG > VCC/2 selected. This output can
be used to notify an active system to perform a power-up
initialization routine.
Shutting Off with a Long PB Press
The LTC2956 can be put into the low power SHUTDOWN
mode by holding the push button PB input low for a duration longer than tLONG. The tLONG can be adjusted with
the resistive divider at the LONG pin. Figure 7 shows the
timing during a long press. After the tLONG timeout, the
part enters the Shutting Off state, and the OFFALERT pin
is pulled low. This state persists for tOFF (typically 1s) thus
SLEEP
allowing an active system to perform power down tasks
before the enable output is pulled low.
If the push button input is held low for a duration shorter
than tLONG, the LTC2956 pulls EN high but does not enter
the Shutting off state. Once PB is released, the LTC2956
pulls the EN output low if the SLEEP pin has pulsed once
or if tONMAX has timed out. This short press can be used
to override the timer for early wake-up or it can be used
with the PBOUT output to drive the software menu.
Pressing the pushbutton will always restart the tPERIOD
timer. This is useful for manual synchronization of the
wake-up time with an external event. When the external
event occurs, a short press will turn on the system and
the next turn on will be tPERIOD later.
IGNORED
0V
tAWAKE_MIN
PB
tDB
EN
PBOUT
OFFALERT
TLONG
START
STOP
tOFF
tLONG
RESTART
tPERIOD TIMER
STOP
HELD IN RESET BY PB
TONMAX
STATE
SLEEP
AWAKE
SHUTTING OFF
OFF
2956 F07
Figure 7. Holding PB Low to Enter SHUTDOWN Mode
14
2956fa
For more information www.linear.com/LTC2956
LTC2956
OPERATION
SLEEP
IGNORED
0V
tAWAKE_MIN
tOFF
EN
OFFALERT
TLONG
STOP
tLONG
tPERIOD TIMER
RESTART
STOP
tONMAX MUST BE LONGER THAN
tLONG TO ALLOW TRANSITION TO
SHUTDOWN MODE
TONMAX
STATE
SLEEP
AWAKE
SHUTTING OFF
OFF
2956 F08
Figure 8. Holding SLEEP High to Enter SHUTDOWN Mode
Shutting Off with a Long SLEEP Pulse
In an active system, the LTC2956 can also be placed into
the low power SHUTDOWN mode by holding SLEEP high
for a duration greater than tLONG (Figure 8). The OFFALERT
pin is pulled low when tLONG times out and remains low
during the Shutting Off state. Unlike a long push button
press event, however, the tONMAX timer remains enabled
while SLEEP is pulled high. If tONMAX is adjusted to be
less than tLONG, a long SLEEP pulse can never trigger a
shutdown.
If the SLEEP pulse width is shorter than tLONG, the LTC2956
pulls the EN output high but does not enter the Shutting
Off state. Once SLEEP goes low (or if tONMAX times out
first), the EN output goes low and the device enters the
Sleep state.
Pulling SLEEP High During the Sleep State
During the Sleep state, the system can prompt the LTC2956
to enter the Awake state by pulling SLEEP pin high even if
the tPERIOD time is not up. This is illustrated in Figure 9.
The LTC2956 automatically restarts the tPERIOD timer when
it enters the Awake state in response to the logic high on
the SLEEP input.
Upon entering the Sleep state, the LTC2956 ignores all
inputs for tSLEEP_MIN. This allows time for the system’s
power supply to fully discharge before it is allowed to turn
on again. If the system pulls SLEEP high during tSLEEP_MIN,
the LTC2956 will wait until tSLEEP_MIN expires before reentering the Awake state.
Prolonging Awake Time
The LTC2956 restarts the tPERIOD timer on every rising edge
of EN. This allows the Awake time, tAWAKE to vary from cycle
to cycle while the turn-on period stay constant. However, if
tAWAKE extends toward or beyond tPERIOD, the next Awake
state may be delayed due to the minimum Sleep duration,
tSLEEP_MIN (128ms typically). This tSLEEP_MIN ensures that
the system supply has sufficient time to discharge. Refer
to Figure 10, the second Awake time is longer, resulting
in a longer tPERIOD due to tSLEEP_MIN.
2956fa
For more information www.linear.com/LTC2956
15
LTC2956
OPERATION
EN
IGNORED
SLEEP
IGNORED
tAWAKE_MIN
tSLEEP_MIN
tPERIOD TIMER
tSLEEP_MIN
RESTART
TONMAX
AWAKE
STATE
SLEEP
AWAKE
SLEEP
2956 F09
Figure 9. Pulling the SLEEP Input High to Enter Awake State
PROLONGED TURN-ON TIME
NORMAL TURN-ON TIME
EN
SLEEP
tSLEEP_MIN
tSLEEP_MIN
STOP
tPERIOD TIMER
tPERIOD
tPERIOD
tPERIOD
DELAY DUE
TO tSLEEP_MIN
TONMAX
STATE
AWAKE
SLEEP
AWAKE
SLEEP
AWAKE
SLEEP
2956 F10
Figure 10. Prolonged Awake State
Push Button Debounce and PBOUT
The PB input is debounced by an internal timer. This debounced signal is available at the PBOUT open drain output,
and it can be used to interrupt the system for software
purposes such as choosing an option from a menu. The
initial PBOUT pulse in Awake state typically has a width
of at least tPBOUT_FIRST (128ms typical) which allows the
16
system sufficient time to respond just after powering up
(see Figure 11). Subsequent PBOUT pulses have a width
of at least tPD_DB (32ms typical). Note that if the system’s
microcontroller toggles SLEEP during tPBOUT_FIRST, the
LTC2956 will enter the Sleep state and release PBOUT
high without waiting for tPBOUT_FIRST to complete.
2956fa
For more information www.linear.com/LTC2956
LTC2956
OPERATION
SLEEP
IGNORED
0V
IGNORED
IGNORED
tAWAKE_MIN
PB
32ms
32ms
32ms
32ms
32ms
EN
PBOUT
>32ms
tPBOUT_FIRST
>32ms
OFFALERT
START
TLONG
START
STOP
START
STOP
STOP
tLONG
HELD IN
RESET BY PB
TONMAX
STATE
SLEEP
HELD IN
RESET BY PB
HELD IN
RESET BY PB
AWAKE
SLEEP
2956 F11
Figure 11. PBOUT Echoing Debounced PB
APPLICATIONS INFORMATION
Configuration
Configuring the LTC2956 wake-up timer is a 3-step process.
The wake-up timer period is determined by the resistor to
ground at the PERIOD pin and the resistive divider at the
RANGE pin. Then the minimum time required for a long
push button press that forces the wake-up timer into the
SHUTDOWN mode is determined by another resistive
divider at the LONG pin. Finally, the maximum awake time
(tONMAX) is set with a capacitor to GND at the ONMAX pin.
The LTC2956 biases and samples the voltages or current
at these pins once every 66s while in RUN mode. The part
also samples these pins following power-up and when in
from Off state.
Step 1: Set tPERIOD with resistors at the PERIOD and
RANGE pins
The required resistance value at the PERIOD pin to set
the wake-up timer period can be determined as follows:
RPERIOD = 400 • tPERIOD/NRANGE [kΩ/s]
NRANGE is the internal clock divider and can be adjusted
through the resistive divider at the RANGE pin as shown
in Table 1. It is advisable to select an NRANGE value that
yields the largest allowable RPERIOD value. The LTC2956’s
oscillator can run with values of RPERIOD ranging from
32.4kΩ to 324kΩ.
For example, if a tPERIOD of 3s is desired, RPERIOD = 75k
and NRANGE = 16 could be used, but RPERIOD = 300k and
NRANGE = 4 is a better choice.
2956fa
For more information www.linear.com/LTC2956
17
LTC2956
APPLICATIONS INFORMATION
Table 1. RANGE Programming
RECOMMENDED tPERIOD
NRANGE
RRANGE* [kΩ]
0.25s to 0.8s
1
9.76
0.4s to 3.2s
4
17.4
1.6s to 12.8s
16
26.1
6.4s to 51.2s
64
35.7
25.6s to 3.4min
256
47.5
102s to 14min
1,024
61.9
6.8min to 55min
4,096
78.7
27min to 3.6hr
16,384
100
1.82hr to 15hr
65,536
127
7.28hr to 58hr
262,144
162
29hr to 233hr
1,048,576
210
233hr to 932hr
4,194,304
280
*RCOM = 100kΩ
Step 2: Set required pushbutton time for shutdown with
the resistive divider at the LONG pin
The resistive divider at the LONG pin sets the tLONG value
and Power Up mode as shown in Table 2:
Table 2. tLONG Programming
tLONG
POWER UP MODE
RLONG* [kΩ]
0.128s
SHUTDOWN
9.76
0.256s
SHUTDOWN
17.4
0.512s
SHUTDOWN
26.1
1.024s
SHUTDOWN
35.7
2.048s
SHUTDOWN
47.5
4.096s
SHUTDOWN
61.9
8.192s
SHUTDOWN
78.7
16.384s
SHUTDOWN
100
0.128s
RUN
127
0.256s
RUN
162
0.512s
RUN
210
1.024s
RUN
280
2.048s
RUN
383
4.096s
RUN
576
8.192s
RUN
1020
16.384s
RUN
Open
*RCOM = 100kΩ
18
Step 3: Set maximum Awake time using capacitor at
ONMAX pin
The value of CONMAX can be determined by the equation:
CONMAX = tONMAX • 75 [nF/s]
For example, a tONMAX of 133ms requires a 10nF capacitor.
High Voltage PowerPath™ Switching
The high voltage EN open drain output of the LTC2956-2
is designed to switch on/off an external power P-channel
MOSFET. This allows a user to connect/disconnect a power
supply (or battery) to its load by toggling the PB pin.
Figure 12 shows the LTC2956-2 switching a 24V battery
application. R6 slows down the turning on of M1 so as
to limit the inrush current when needed to charge up the
capacitor at VOUT. R5 is optional – it helps to speed up
the turning off of M1 and also to keep M1 off when the
input voltage rise time is fast.
+
+
M1
12V
LEAD-ACID
BATTERIES
PB
+
D1
12V
R5*
100k
C1
100nF
VIN
R6
100k
VOUT
COUT
EN
PBOUT
GND
CONMAX
RPERIOD
*R5 IS OPTIONAL
LTC2956-2
ONMAX
PERIOD
ONALERT
OFFALERT
SLEEP
LONG RANGE
RLONG
100k RRANGE
2956 F12
Figure 12. Switching 24V Battery Stack with
External P-Channel MOSFET
PB Pin in a Noisy Environment
The rugged PB pin is designed to operate in noisy environments. Transients below ground and above VIN
will not damage the PB pin. Additionally, the PB pin can
withstand ESD HBM strikes of up to ±25kV. However, if
the pushbutton switch is located physically far from the
2956fa
For more information www.linear.com/LTC2956
LTC2956
APPLICATIONS INFORMATION
LTC2956 PB pin, the parasitic capacitance and parasitic
series inductance of the connecting cable or PCB trace
can cause erratic behavior. The parasitic capacitance can
couple external noise onto the PB input; placing a 0.1μF
capacitor at the pin lessens the impact of this coupling.
The parasitic series inductance may cause unpredictable
ringing at the PB pin; placing a 5.1k resistor from the PB
pin to the pushbutton switch reduces this ringing. Figure
13 shows an example of this RC network at the PB pin.
External Pull-Up Resistor on PB Pin
An internal 900k pull-up resistor on the PB pin makes an
external pull-up resistor unnecessary. Leakage current on
the PB board trace, however, will affect the open circuit
voltage on the PB pin. If the leakage is too large (>2μA),
the PB voltage may fall close to the threshold window. To
mitigate the effect of board leakage, a 10k pull-up resistor
to VIN can be used (see Figure 14).
VIN
PARASITICS
TRACE
CAPACITANCE
VIN
R8
5.1k
NOISE
C5
0.1µF
TRACE
INDUCTANCE
PB
LTC2956-1
GND
2956 F13
Figure 13. Noisy PB Trace
VCC
VIN
VIN
R8
10k
EXTERNAL BOARD
LEAKAGE CURRENT
LTC2956-1/
LTC2956-2
Enhancing VIN Ruggedness and Reverse Battery
Protection
Placing a 1k resistor and a 10nF capacitor at the VIN pin can
be used to enhance ruggedness in some applications (see
Figure 15). The peak operating current of the LTC2956 is
less than 10μA, creating an insignificant 10mV drop across
the 1k resistor. The 10nF bypass capacitor in combination
with the 1k series resistor can protect against high voltage
input transients that momentarily exceed the 40V absolute
maximum voltage rating of the VIN pin. These can occur
during hot-plugging into a battery or AC adapter. This R-C
filter can also protect against transients that may appear
on the PCB ground during large ESD strikes at the PB pin.
A 1k resistor in series with the VIN pin also allows the
LTC2956 to withstand reverse-input voltages up to –40V.
The LTC2956’s VIN pin is internally clamped to one diode
voltage below ground and can tolerate up to 50mA of
reverse current. In applications where a battery could
be inserted backwards, this resistor will limit the reverse
current to a safe level thus allowing internal clamping to
protect the pin.
Figures 16a and 16b shows some additional simple reverse battery protection circuits that use a single MOSFET.
Figure 16a illustrates a high-side PMOS in the power
path while Figure 16b shows a low-side NMOS in the
ground path. In each circuit, the MOSFET body diode is
orientated in the direction of normal current flow. When
the battery is installed incorrectly, the NMOS/PMOS gate
is low/high, thus preventing the circuit from turning on.
When the battery is properly installed, the NMOS/PMOS
FET gate voltage is taken high/low, and its channel shorts
out the diode.
900k
PB
TO LOAD
R7
1k
C1
10nF
>2µA
0.9V
GND
PB
2956 F13
VIN
LTC2956-1
Figure 14. External Pull-Up Resistor on PB Pin for
Board Leakage Greater than 2µA
GND
2956 F15
Figure 15. Enhancing VIN Ruggedness
2956fa
For more information www.linear.com/LTC2956
19
LTC2956
APPLICATIONS INFORMATION
+
+
C1
100nF
R20
10k
PB
R20
10k
VIN
C1
100nF
PB
LTC2956
LOAD
VIN
LTC2956
GND
LOAD
GND
2956 F16a
2956 F16b
Figure 16a. PMOS Reverse Battery Protection
Figure 16b. NMOS Reverse Battery Protection
Interface with Switching Regulators
The LTC2956-1 EN pin can be connected directly to most
switching regulator SHUTDOWN inputs. The EN pin high
level output voltage (VEN(VOH)) is typically 3.3V when
VIN > 3.5V, and VEN(VOH) = VIN – 0.1V if VIN <3.0V. With
a minimum VIN of 1.5V, VEN(OH) is still higher than most
SHUTDOWN thresholds. Figure 17 shows one such application. The LTC3528 regulator is a boost converter
with a SHUTDOWN high threshold of 0.88V (maximum).
If a higher VEN(VOH) is required, an external pull-up
resistor can be connected from the EN pin to any higher
voltage (<36V). The EN pin is designed to be able to sink
at least 1mA of current during turn-off, so this external
pull-up resistor value must be selected to source less
than 1mA with EN at 0V. The LTC2956-1 EN pin can also
be connected to switching regulators with a RUN/SS pin.
RUN/SS typically has a dual function of a SHUTDOWN
threshold and soft-start. Switching regulators optimized for
4.7µH
SW
VIN
1.5V TO 3.2V
LTC3528
VOUT
VIN
4.7µF
PB
VIN
EN
PBOUT
GND
CONMAX
RPERIOD
499k
PGOOD
22pF
22µF
VOUT
3.3V, 0.4A
FB
SHDN
GND
287k
LTC2956-1 ONALERT
OFFALERT
ONMAX
PERIOD
LONG RANGE
RLONG
100k
SLEEP
RRANGE
2956 F17
Figure 17. 2-Cell with 3.3V Output
20
2956fa
For more information www.linear.com/LTC2956
LTC2956
APPLICATIONS INFORMATION
micro-power applications may require an external pull-up
resistor and capacitor to create a soft-start ramp. The EN
pin’s integrated 900k pull-up resistance and an external
capacitor can be used for this purpose. Figure 18 shows
the LTC2956-1 EN pin connected to an LT8610 step-down
regulator’s EN/UV pin.
VIN
5.5V TO 25V
CIN
Layout Considerations
Figure 19 shows example PCB layouts for the QFN and MS
packages with external components. Position the bypass
capacitor close to the LTC2956 on the same side of the
PCB, and keep the traces short in order to give the best
protection against PB pin ESD transients.
VIN
TR/SS
BST
0.22µF
EN/UV
10nF
SW
INTVCC
RT
LT8610
PG
18.2k
BIAS
SYNC
GND
VIN
5V AT 2.5A
1M
FB
PGND
1µF
PB
L1
2.2µH
243k
10pF
47µF
EN
PBOUT
GND
CONMAX
RPERIOD
LTC2956-1
ONALERT
µP
OFFALERT
ONMAX
SLEEP
PERIOD
LONG RANGE
RLONG
100k
2956 F18
RRANGE
Figure 18. Enabling a Micropower DC/DC Converter
LTC2956UD
LTC2956MS
12 11 10
1
1
2
3
4
5
6
9
13
2
8
3
7
4
5
VIN
6
CVIN
CVIN
VIN
12
11
10
9
8
7
GND
GND
2956 F19
Figure 19. Recommended Layout for the VIN Bypass Capacitor
2956fa
For more information www.linear.com/LTC2956
21
LTC2956
TYPICAL APPLICATIONS
Micropower LED Beacon
2.2µF
+
C1+
VIN
C1
2.2µF
C1–
C2+
C2–
CPO
EN1
VIN
PB
GND
EN2
EN
PBOUT
LTC2956-1
ONMAX
PERIOD
LONG RANGE
RPERIOD
250k
RLONG
35.7k
4.7µF
LTC3216
LED1
ONALERT
ILED
OFFALERT
CONMAX
10nF
2.2µF
RCOM
100k
ISET1 ISET2
SLEEP
20k
GND
6.65k
RRANGE
26.1k
tLONG = 1s, tONMAX = 133ms, tPERIOD = 10s
2956 TA02
Micropower Overtemperature Detector
M1
+
C1
100nF
100nF
R5
100k
VCC
R6
100k
D+
470pF
D–
PB
VIN
GND
EN
PBOUT
LTC2956-2
YELLOW
LED1
ONALERT
ONMAX
PERIOD
RPERIOD
100k
LONG RANGE
LTC2996
VREF
VTH
9.76k
SLEEP
tLONG = 1s, tONMAX = 133ms, tPERIOD = 4s
RCOM
100k
RRANGE
26.1k
UT
VTL
147 k
RLONG
35.7k
VPTAT
20.5k
OFFALERT
CONMAX
10nF
GND
OT
FAULT AT 125°C
D1
BAS116
tALERT
22
Q1
MMBT
3904
2956 TA03
2956fa
For more information www.linear.com/LTC2956
LTC2956
TYPICAL APPLICATIONS
Micropower, Reverse Battery Protected Pushbutton Controller and Sleep Timer with Hot-Swap Controller
RSENSE
45mΩ
25V
Z1*
M2
OUT
+
OV = 29.4V
UVH = 25.1V
UVL = 24.6V
R7
1k
C1
10nF
M1
1A LOAD
COUT
100µF
SENSE GATE
VIN
PB
GND
1.21M
EN
LTC2956-1
PBOUT
ONALERT
CONMAX
82nF
PERIOD
RPERIOD
88.7k
LONG RANGE
SLEEP
100k
UVL
845Ω
LTC4231
UVH
OFFALERT
ONMAX
SOURCE
IN
STATUS
5.9k
OV
34.8k
RLONG
383k
RCOM RRANGE
100k
100k
tLONG = 2s, tONMAX = 1s, tPERIOD = 1 HOUR
LTC2956 FORCED INTO OFF MODE IF LTC4231 FAILS
TO POWER-UP WITHIN 1s OF EN RISING-EDGE
GNDSW
SHDN GND
TIMER
CT
82nF
D1
BAS116
2956 TA04
2956fa
For more information www.linear.com/LTC2956
23
LTC2956
TYPICAL APPLICATIONS
Micropower Time-Lapse Photography Intervalometer
LITHIUM
CELL
+
SHUTTER
C1
100nF
VIN
PB
GND
EN
PBOUT
LTC2956-1
ONALERT
OFFALERT
ONMAX
CONMAX
10nF
PERIOD
RPERIOD
100k
LONG RANGE
RLONG
35.7k
RCOM
100k
tLONG = 1s, tONMAX = 133ms
SLEEP
17.4k
35.7k
61.9k
2956 TA05
0.25s
9.76k
26.1k
47.5k
100k
78.7k
162k
127k
280k
210k
1s
4s
16s
64s
256s
1 HOUR, 8 MINUTES
4 HOURS, 33 MINUTES
R4[1:12]
24
tPERIOD
17 MINUTES
18 HOURS, 12 MINUTES
3 DAYS, 49 MINUTES
12 DAYS, 3 HOURS
2956fa
For more information www.linear.com/LTC2956
LTC2956
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
UD Package
12-Lead Plastic QFN (3mm × 3mm)
(Reference LTC DWG # 05-08-1855 Rev Ø)
0.70 ±0.05
3.50 ±0.05
1.65 ±0.05
2.10 ±0.05 (4 SIDES)
PACKAGE OUTLINE
0.25 ±0.05
0.50 BSC
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
3.00 ± 0.10
(4 SIDES)
BOTTOM VIEW—EXPOSED PAD
PIN 1 NOTCH R = 0.20 TYP
OR 0.25 × 45° CHAMFER
R = 0.115
TYP
0.75 ±0.05
11
12
PIN 1
TOP MARK
(NOTE 6)
0.40 ±0.10
1
2
1.65 ±0.10
(4-SIDES)
(UD12) QFN 0709 REV Ø
0.200 REF
0.00 – 0.05
NOTE:
1. DRAWING CONFORMS TO JEDEC PACKAGE OUTLINE MO-220 VARIATION (WEED-1)
2. DRAWING NOT TO SCALE
3. ALL DIMENSIONS ARE IN MILLIMETERS
4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE
MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE
5. EXPOSED PAD SHALL BE SOLDER PLATED
6. SHADED AREA IS ONLY A REFERENCE FOR PIN 1 LOCATION
ON THE TOP AND BOTTOM OF PACKAGE
0.25 ±0.05
0.50 BSC
2956fa
For more information www.linear.com/LTC2956
25
LTC2956
PACKAGE DESCRIPTION
Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings.
MS Package
12-Lead Plastic MSOP
(Reference LTC DWG # 05-08-1668 Rev A)
4.039 ±0.102
(.159 ±.004)
(NOTE 3)
0.889 ±0.127
(.035 ±.005)
5.10
(.201)
MIN
12 11 10 9 8 7
0.254
(.010)
3.20 – 3.45
(.126 – .136)
DETAIL “A”
3.00 ±0.102
(.118 ±.004)
(NOTE 4)
4.90 ±0.152
(.193 ±.006)
0° – 6° TYP
0.406 ±0.076
(.016 ±.003)
REF
GAUGE PLANE
0.42 ±0.038
(.0165 ±.0015)
TYP
0.53 ±0.152
(.021 ±.006)
0.65
(.0256)
BSC
RECOMMENDED SOLDER PAD LAYOUT
DETAIL “A”
0.18
(.007)
SEATING
PLANE
1.10
(.043)
MAX
0.22 – 0.38
(.009 – .015)
TYP
1 2 3 4 5 6
0.650
NOTE:
(.0256)
1. DIMENSIONS IN MILLIMETER/(INCH)
BSC
2. DRAWING NOT TO SCALE
3. DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS.
MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
4. DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS.
INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.152mm (.006") PER SIDE
5. LEAD COPLANARITY (BOTTOM OF LEADS AFTER FORMING) SHALL BE 0.102mm (.004") MAX
26
0.86
(.034)
REF
0.1016 ±0.0508
(.004 ±.002)
MSOP (MS12) 0213 REV A
2956fa
For more information www.linear.com/LTC2956
LTC2956
REVISION HISTORY
REV
DATE
DESCRIPTION
A
07/15
Minor Edits
PAGE NUMBER
4, 6, 16, 22
2956fa
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection
of its circuits
as described
herein will not infringe on existing patent rights.
For more
information
www.linear.com/LTC2956
27
LTC2956
TYPICAL APPLICATION
Low IQ Timer with 10% Duty Cycle
VIN
100nF
tPERIOD = 280ms, 10% DUTY CYCLE
VIN
ONMAX
2.2nF
PB
EN
PBOUT
ONALERT
LTC2956-1
GND
OFFALERT
SLEEP
LONG
RANGE
100k
PERIOD
9.76k
113k
tONMAX = 29ms, tPERIOD = 280ms
2956 TA06
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC2900
Adjustable Quad Supply Monitor
Adjustable RESET, 10-Lead MSOP and 3mm × 3mm DFN Packages
LTC2904/LTC2905 Pin-Adjustable Dual Supply Monitors
Adjustable RESET and Tolerance, 8-Lead SOT-23 and 3mm × 2mm DFN
Packages
LTC2909
Precision Triple/Dual Input UV, OV and Negative
Voltage Monitor
6.5V Shunt Regulator for High Voltage Operation
LTC2910
Octal Positive/Negative Voltage Monitor
Eight Adjustable Inputs (0.5V)
LTC2914
Quad UV/OV Positive/Negative Voltage Monitor
Adjustable UV and OV Trip Values
LTC2950/LTC2951 Pushbutton On/Off Controllers
High Voltage, Low Power Pushbutton Controllers with Power-Down Fault
Detect KILL Timer
LTC2952
Pushbutton PowerPath Controller with Supervisor
Automatic Low Loss Switchover Between DC Sources
LTC2953
Pushbutton Controller with Voltage Monitoring
Adjustable Supply Monitor with 200ms Reset
LTC2954
Pushbutton On/Off Controller with μP Interrupt
Adjustable Turn On/Off Timers
LTC2955
Pushbutton On/Off Controller with Automatic Turn-On
1.2μA Supply Current
LTC4411
2.6A Low Loss Ideal Diode in ThinSOT™
No External MOSFET, Automatic Switching Between DC Sources
LTC4412HV
PowerPath Controller in ThinSOT
Efficient Diode-ORing, Automatic Switching Between DC Sources, 3V to 36V
LTC4055
USB Power Controller and Li-Ion Charger
Automatic Switchover, Charges 1-Cell Li-Ion Batteries
LTC4352
Ideal Diode Controller with Monitoring
Controls N-Channel MOSFET, 0V to 18V Operation
28 Linear Technology Corporation
1630 McCarthy Blvd., Milpitas, CA 95035-7417
For more information www.linear.com/LTC2956
(408) 432-1900 ● FAX: (408) 434-0507
●
www.linear.com/LTC2956
2956fa
LT 0715 REV A • PRINTED IN USA
 LINEAR TECHNOLOGY CORPORATION 2015