LTC2915/LTC2916
Voltage Supervisor with
27 Selectable Thresholds
FEATURES
DESCRIPTION
n
The LTC®2915/LTC2916 are low voltage single-supply
monitors with selectable thresholds. The parts operate
from 1.5V to 5.5V and consume a quiescent current of
only 30μA.
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n
n
n
n
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n
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9 Selectable Supply Voltages
12V, 5V, 3.3V, 2.5V, 1.8V
1.5V, 1.2V, 1.0V, +ADJ (0.5V)
3 Selectable Tolerances
–5%, –10%, –15% (LTC2915)
Manual Reset Input (LTC2916)
1.5V to 5.5V Supply Operation
6.2V Shunt Regulator for High Voltage Operation
Guaranteed Operation to 125˚C
Guaranteed Threshold Accuracy: ±1.5%
Low Quiescent Current: 30μA Typical
Power Supply Glitch Immunity
Guaranteed RST for VCC ≥ 0.8V
Low Profile (1mm) 8-Lead TSOT-23 (ThinSOTTM) and
(3mm × 2mm) DFN Packages
APPLICATIONS
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Two three-state inputs select one of nine internally programmed thresholds without the need for external resistors.
For the LTC2915, an additional three-state input determines
the tolerance (–5%, –10%, –15%). The tolerance for the
LTC2916 is fixed at –5%. Threshold accuracy is guaranteed
at ±1.5% over the entire operating temperature range.
Glitch filtering ensures reliable reset operation without
false triggering.
The reset timeout may be set to 200ms or adjusted using
an external capacitor. A separate manual reset input on the
LTC2916 allows a simple push button interface.
Operation to 125°C makes the LTC2915 and LTC2916
suitable for automotive applications.
Handheld Devices
Cell Phone Base Stations
Automotive Control Systems
Network Servers
Optical Networking Systems
L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
ThinSOT is a trademark of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATION
1.8V, –5% Tolerance Supply Monitor
Monitor Selection Table
1.8V
10k
LTC2916
VM
RST
RT
SEL1
SEL2
MR
GND
SEL2
12V
VCC
VCC
5V
VCC
Open
μP
3.3V
VCC
GND
2.5V
Open
VCC
1.8V
Open
Open
1.5V
Open
GND
1.2V
GND
VCC
1V
GND
Open
ADJ (0.5V)
GND
GND
RESET
tRST = 200ms
SEL1
VCC
0.1μF
VCC
NOMINAL VOLTAGE
29156 TA01
29156fa
1
LTC2915/LTC2916
ABSOLUTE MAXIMUM RATINGS (Notes 1, 2)
Terminal Voltages
VCC (Note 3).......................................... –0.3V to 5.7V
SEL1, SEL2, TOL, MR, RST .................. –0.3V to 7.5V
VM ......................................................... –0.3V to 15V
RT .............................................–0.3V to (VCC + 0.3)V
Terminal Currents
VCC (Note 3).......................................................±5mA
Operating Temperature Range
LTC2915C/LTC2916C ............................... 0°C to 70°C
LTC2915I/LTC2916I.............................. –40°C to 85°C
LTC2915H/LTC2916H ......................... –40°C to 125°C
Storage Temperature Range................... –65°C to 150°C
TS8 Lead Temperature (Soldering, 10 sec) ........... 300°C
PIN CONFIGURATION
TOP VIEW
TOP VIEW
VM 1
SEL1 2
TOL/MR 3
GND 4
8 VCC
7 SEL2
6 RT
5 RST
GND 1
8
RST
TOL/MR 2
7
RT
6
SEL2
5
VCC
SEL1 3
9
VM 4
TS8 PACKAGE
8-LEAD PLASTIC TSOT-23
DDB PACKAGE
8-LEAD (3mm s 2mm) PLASTIC DFN
TOL FOR LTC2915
MR FOR LTC2916
TJMAX = 150°C, θJA = 250°C/W
TOL FOR LTC2915
MR FOR LTC2916
TJMAX = 150°C, θJA = 76°C/W
EXPOSED PAD (PIN 9) PCB GND CONNECTION OPTIONAL
ORDER INFORMATION
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2915CTS8-1#PBF
LTC2915ITS8-1#PBF
LTC2915HTS8-1#PBF
LTC2915CDDB-1#PBF
LTC2915IDDB-1#PBF
LTC2915HDDB-1#PBF
LTC2915CTS8-1#TRPBF
LTC2915ITS8-1#TRPBF
LTC2915HTS8-1#TRPBF
LTC2915CDDB-1#TRPBF
LTC2915IDDB-1#TRPBF
LTC2915HDDB-1#TRPBF
LTCVQ
LTCVQ
LTCVQ
LCVR
LCVR
LCVR
8-Lead TSOT-23
8-Lead TSOT-23
8-Lead TSOT-23
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
LEAD FREE FINISH
TAPE AND REEL
PART MARKING*
PACKAGE DESCRIPTION
TEMPERATURE RANGE
LTC2916CTS8-1#PBF
LTC2916ITS8-1#PBF
LTC2916HTS8-1#PBF
LTC2916CDDB-1#PBF
LTC2916IDDB-1#PBF
LTC2916HDDB-1#PBF
LTC2916CTS8-1#TRPBF
LTC2916ITS8-1#TRPBF
LTC2916HTS8-1#TRPBF
LTC2916CDDB-1#TRPBF
LTC2916IDDB-1#TRPBF
LTC2916HDDB-1#TRPBF
LTDCW
LTDCW
LTDCW
LDCX
LDCX
LDCX
8-Lead TSOT-23
8-Lead TSOT-23
8-Lead TSOT-23
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
8-Lead (3mm × 2mm) Plastic DFN
0°C to 70°C
–40°C to 85°C
–40°C to 125°C
0°C to 70°C
–40°C to 85°C
–40°C to 125°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 non-standard 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/
29156fa
2
LTC2915/LTC2916
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 2.5V, unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
VCC(MIN)
Supply Voltage for Guaranteed RST Low RST Driven Low
CONDITIONS
l
MIN
VCC(UVLO)
Supply Undervoltage Lockout
l
VCC(SHUNT)
Shunt Regulation Voltage
IVCC = 0.5mA
l
ICC
VCC Pin Current
SEL1, SEL2, TOL, MR = Open
SEL1, SEL2, TOL = GND (LTC2915)
MR = VCC (LTC2916)
l
l
TYP
MAX
0.8
5.7
UNITS
V
1.5
V
6.2
7.0
V
30
45
50
80
μA
μA
Monitor Input (VM)
VMT120
12V, 5% Reset Threshold
12V, 10% Reset Threshold
12V, 15% Reset Threshold
l
l
l
11.04
10.44
9.84
11.22
10.62
10.02
11.40
10.80
10.20
V
V
V
VMT50
5V, 5% Reset Threshold
5V, 10% Reset Threshold
5V, 15% Reset Threshold
l
l
l
4.600
4.350
4.100
4.675
4.425
4.175
4.750
4.500
4.250
V
V
V
VMT33
3.3V, 5% Reset Threshold
3.3V, 10% Reset Threshold
3.3V, 15% Reset Threshold
l
l
l
3.036
2.871
2.706
3.086
2.921
2.756
3.135
2.970
2.805
V
V
V
VMT25
2.5V, 5% Reset Threshold
2.5V, 10% Reset Threshold
2.5V, 15% Reset Threshold
l
l
l
2.300
2.175
2.050
2.338
2.213
2.088
2.375
2.250
2.125
V
V
V
VMT18
1.8V, 5% Reset Threshold
1.8V, 10% Reset Threshold
1.8V, 15% Reset Threshold
l
l
l
1.656
1.566
1.476
1.683
1.593
1.503
1.710
1.620
1.530
V
V
V
VMT15
1.5V, 5% Reset Threshold
1.5V, 10% Reset Threshold
1.5V, 15% Reset Threshold
l
l
l
1.380
1.305
1.230
1.403
1.328
1.253
1.425
1.350
1.275
V
V
V
VMT12
1.2V, 5% Reset Threshold
1.2V, 10% Reset Threshold
1.2V, 15% Reset Threshold
l
l
l
1.104
1.044
0.984
1.122
1.062
1.002
1.140
1.080
1.020
V
V
V
VMT10
1V, 5% Reset Threshold
1V, 10% Reset Threshold
1V, 15% Reset Threshold
l
l
l
0.920
0.870
0.820
0.935
0.885
0.835
0.950
0.900
0.850
V
V
V
VMTADJ
ADJ (0.5V), 5% Reset Threshold
ADJ (0.5V), 10% Reset Threshold
ADJ (0.5V), 15% Reset Threshold
l
l
l
460.0
435.0
410.0
467.5
442.5
417.5
475.0
450.0
425.0
mV
mV
mV
RVM
VM Input Impedance (Note 4)
Fixed Threshold Modes
l
0.5
8
MΩ
IVM(ADJ)
ADJ Input Current
VM = 0.5V
l
±15
nA
0.5
V
Three-State Inputs (SEL1, SEL2), (TOL, LTC2915)
VTPIN,LOW
Low Level Input Voltage
l
VTPIN,HIGH
High Level Input Voltage
l
VTPIN,Z
Pin Voltage when Open
ITPIN,Z
Allowable Leakage in Open State
ITPIN,H/L
Pin Input Current
ITPIN = 0μA
VTPIN = 0V, VCC
1.4
V
0.9
V
l
±5
μA
l
±20
μA
29156fa
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LTC2915/LTC2916
ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 2.5V, unless otherwise noted. (Note 2)
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Reset Timer Control (RT)
IRT(UP)
RT Pull-Up Current
VRT = 0.25V
l
–2
–3
–4
μA
IRT(DOWN)
RT Pull-Down Current
VRT = 1.1V
l
2
3
4
μA
IRT(INT)
Internal RT VCC Detect Current
VRT = VCC
l
1
8
μA
VRT(INT,LH)
RT Internal Timer Threshold
VRT Rising, Referenced to VCC
l
–100
–160
–300
mV
tRST(INT)
Internal Reset Timeout Period
VRT = VCC
l
150
200
260
ms
tRST(EXT)
Adjustable Reset Timeout Period
CRT = 2.2nF
l
16
20
25
ms
tUV
VM Undervoltage Detect to RST
Asserted
VM Less Than Reset Threshold
VMTX by More Than 5%
l
10
80
150
μs
VOL
Output Voltage Low RST
VCC = 3.3V, IRST = 2.5mA
VCC = 1V, IRST = 100μA
VCC = 0.8V, IRST = 15μA
l
l
l
0.15
0.15
0.05
0.4
0.3
0.2
V
V
V
IOH(RST)
RST Output Voltage High Leakage
RST = VCC
l
±1
μA
0.2 • VCC
V
Reset Output (RST)
Manual Reset Input (LTC2916)
VIL
Input Low Voltage
l
VIH
Input High Voltage
l
0.8 • VCC
RPU
Pull Up Resistance
l
50
Pulsewidth
l
250
tPW
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 pins are positive; all voltages are referenced to
GND unless otherwise noted.
V
100
150
kΩ
ns
Note 3: VCC maximum pin voltage is limited by input current. Since the
VCC pin has an internal 6.2V shunt regulator, a low impedance supply
which exceeds 5.7V may exceed the rated terminal current. Operation
from higher voltage supplies requires a series dropping resistor. See
Applications Information.
Note 4: Input impedance is dependent on the configuration of the SEL
pins.
TIMING DIAGRAM
Monitor Input Timing
VM
VMTx
tUV
RST
tRST
1V
29156 TD01
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LTC2915/LTC2916
TYPICAL PERFORMANCE CHARACTERISTICS
Quiescent Supply Current vs
Temperature
1.5
QUIESCENT SUPPLY CURRENT, ICC (μA)
40
0.5
VMTADJ
0
VMT25
–0.5
VMT120
–1.0
–1.5
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
SEL1 = 0V
SEL2 = 2.5V
TOL = OPEN
35
VCC = 5.5V
VCC = 2.5V
30
VCC = 1.5V
25
20
–50
125
–25
75
0
25
50
TEMPERATURE (°C)
100
29156 G01
210
190
170
50
25
0
75
TEMPERATURE (°C)
100
125
ICC = 5mA
6.3
ICC = 1mA
ICC = 100μA
6.2
6.1
–50
RST Output Voltage vs VCC
0
–25
0
25
50
75
TEMPERATURE (°C)
100
125
7.0
6.8
6.6
6.4
6.2
6.0
0.01
3
2
1
0
5
29156 G07
1
0.1
10
SUPPLY CURRENT, ICC (mA)
100
29156 G06
RST Pull-Down Current vs VCC
PULL-DOWN CURRENT, IRST (mA)
RST VOLTAGE (V)
50
29156 G03
RST VOL vs IRST
1.0
6
4
1
2
3
4
SUPPLY VOLTAGE, VCC (V)
100
29156 G05
6
0
150
Shunt Regulation Voltage vs
Supply Current
6.4
29156 G04
100k PULL-UP TO VCC
SEL1 = SEL2 = TOL = 0V
5 VM = 0.5V
RESET OCCURS
ABOVE CURVE
1
10
100
0.1
GLITCH PERCENTAGE PAST THRESHOLD (%)
SHUNT REGULATION VOLTAGE, VCC(SHUNT) (V)
SHUNT REGULATION VOLTAGE, VCC(SHUNT) (V)
RESET TIMEOUT PERIOD (ms), tRST(INT)
230
–25
200
Shunt Regulation Voltage vs
Temperature
RT = VCC
150
–50
250
29156 G02
Internal Reset Timeout Period vs
Temperature
250
300
125
5
NO PULL-UP R
VCC = 2.5V
0.8
RST VOLTAGE (V)
NORMALIZED VMTnn (%)
1.0
Allowable Glitch Duration vs
Magnitude
MAXIMUM ALLOWABLE GLITCH DURATION (μs)
Threshold Voltage vs
Temperature
TA = 25°C unless otherwise noted.
4
RST AT 150mV
3
2
TA = 25°C
0.4
0.2
RST AT 50mV
1
TA = 125°C
0.6
0
0
0
1
2
3
4
SUPPLY VOLTAGE, VCC (V)
5
29156 G08
TA = –40°C
0
2
6
4
IRST (mA)
8
10
29156 G09
29156fa
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LTC2915/LTC2916
PIN FUNCTIONS (TSOT/DFN)
GND (Pin 4/Pin 1): Device Ground.
MR (Pin 3/Pin 2) (LTC2916 only): Manual Reset Input
(Active Low). A low level on the MR input causes the part
to issue a reset, which is released one reset timeout after
the input goes high. The pin has an internal 100k pull-up
to VCC, and thus may interface directly to a momentary
pushbutton. Leave open if unused.
RST (Pin 5/Pin 8): Open Drain RST Output. Asserts low
when VM is below the threshold selected by SEL1, SEL2
and TOL input pins. Held low for an adjustable timeout
after VM input is above threshold.
RT (Pin 6/Pin 7): Reset Timeout Control Pin. Attach an
external Capacitor (CRT) to GND to set a reset timeout of
9ms/nF. Floating RT generates a reset timeout of approximately 400μs. Tie RT to VCC to generate a reset timeout
of approximately 200ms.
SEL1, SEL2 (Pins 2, 7/Pins 3, 6): Monitor Voltage Select
Three-State Inputs. SEL1 and SEL2 control the nominal
threshold voltage that VM is set to monitor. Connect to VCC,
GND or leave unconnected in open state. (See Table 1).
TOL (Pin 3/Pin 2) (LTC2915 only): Three-State Input
for Supply Tolerance Selection (–5%, –10% or –15%).
Controls the tolerance band at which the VM supply is
monitored. Connect to VCC, GND, or leave unconnected
in open state. (See Table 2).
VCC (Pin 8/Pin 5): Power Supply Input. Bypass this pin
to ground with a 0.1μF ceramic capacitor. A minimum of
1.5V on VCC ensures that the part is out of under voltage
lockout and that the voltage thresholds are accurate.
Operates as a direct supply input for voltages up to 5.5V.
Operates as a shunt regulator for supply voltages greater
than 5.7V and should have a resistor between this pin and
the supply to limit VCC input current to no greater than
5mA. When used without a current-limiting resistor, pin
voltage must not exceed 5.7V.
VM (Pin 1/Pin 4): Voltage Monitor Input to RST Comparator. SEL1, SEL2 and TOL inputs select the exact threshold
that asserts the RST output.
Exposed Pad (Pin 9, DFN Only): Exposed Pad may be left
open or connected to device ground.
BLOCK DIAGRAM
LTC2915
SEL1
SEL2
LTC2916
MR
TOL
RT
VCC
3 STATE
DECODE
VCC
VCC DETECT
100k
VCC
6.2V
MONITOR
DIVIDER
MATRIX
VM
+
–
0.5V
REFERENCE
DIVIDER
MATRIX
–
+
INTERNAL
200ms TIMER
RST
RESET
DRIVER LOGIC
GND
ADJUSTABLE
RESET TIMER
29156 BD
29156fa
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LTC2915/LTC2916
APPLICATIONS INFORMATION
Supply Monitoring
The LTC2915/LTC2916 are low voltage single supply
monitors with selectable thresholds. Two three-state inputs
select one of nine internally programmed thresholds. For
the LTC2915, a third three-state input selects the tolerance
at which the supply connected to the VM pin is monitored
(–5%, –10%, –15%). The tolerance for the LTC2916 is
fixed at –5%. Threshold accuracy is guaranteed at ±1.5%
over the entire operating temperature range.
The LTC2915/LTC2916 asserts the RST output low when
VM is below the programmed threshold, and for a reset
timeout (tRST) after VM goes above the threshold. The reset
timeout can be configured to use an internal timer with no
external components, or an adjusted timer programmed
by placing an external capacitor from RT to ground.
Power-Up
VCC powers the drive circuits for the RST pin. Therefore,
as soon as VCC reaches 0.8V during power up, the RST
output asserts low.
The SEL1 and SEL2 three-state input pins should be connected to GND, VCC or left unconnected during normal
operation. Note that when left unconnected, the maximum
leakage allowable from the pin to either GND or VCC is
±5μA.
The tolerance at which the monitored supply is measured
is set by the TOL pin (LTC2915 only), as shown in Table 2.
If desired (e.g. for margining purposes), the TOL pin may
be driven by a three-state buffer. That three-state buffer
must have a VOL and VOH which meet the VIL and VIH of
the TOL pin specified in the Electrical Characteristics, and
maintain less than 5μA of leakage in the open state.
Threshold Accuracy
The trip threshold for VM is selected by configuring the
three-state input pins. When using the adjustable input, an
external resistive divider sets the trip threshold, allowing
the user complete control over the trip point. Selection of
this trip voltage is crucial to the reliability of the system.
Table 1. Voltage Threshold Settings
Until VCC reaches the undervoltage lockout threshold
(guaranteed less than 1.5V), RST is held low regardless
of the state of VM.
NOMINAL VOLTAGE
SEL1
SEL2
12V
VCC
VCC
5V
VCC
Open
Once VCC is above the under voltage lockout threshold
and VM is above the programmed threshold, the reset
timer is started. After the reset timeout (tRST), the open
drain pull-down releases RST and the external pull-up
resistor pulls high.
3.3V
VCC
GND
2.5V
Open
VCC
1.8V
Open
Open
1.5V*
Open
GND
1.2V*
GND
VCC
1V*
GND
Open
ADJ* (0.5V)
GND
GND
Power-Down
On power-down, once VM drops below its threshold or
VCC drops below the undervoltage lockout, RST asserts
logic low.
Monitor Threshold Control
The monitor threshold on the VM pin is controlled by
the SEL1, SEL2 and TOL three-state pins. The SEL1 and
SEL2 pins select one of nine preset nominal voltages
(including one externally adjustable threshold) as shown
in Table 1.
*Require a separate supply for VCC
Table 2. System Voltage Tolerance Settings
TOLERANCE
TOL
–5%
VCC
–10%
Open
–15%
GND
29156fa
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LTC2915/LTC2916
APPLICATIONS INFORMATION
Any power supply has some tolerance band within which
it is expected to operate (e.g. 5V±10%). It is generally
undesirable that a supervisor issue a reset when the power
supply is inside this tolerance band. Such a “nuisance”
reset reduces reliability by preventing the system from
functioning under normal conditions.
To prevent nuisance resets, the supervisor threshold must
be guaranteed to lie outside the power supply tolerance
band. To ensure that the threshold lies outside the power
supply tolerance range, the nominal threshold must lie outside that range by the monitor’s accuracy specification.
All 27 of the selectable thresholds have the same relative
threshold accuracy of ±1.5% of the programmed nominal
input voltage (over the full operating temperature range).
Consider the example of monitoring a 5V supply with a 10%
tolerance. The nominal threshold internal to the LTC2915
is 11.5% below the 5V input at 4.425V. With ±1.5% accuracy, the trip threshold range is 4.425V±75mV over
temperature (i.e. 10% to 13% below 5.0V). The monitored
system must thus operate reliably down to 4.35V or 13%
below 5.0V over temperature.
Glitch Immunity
The above discussion is concerned only with the DC
value of the monitored supply. Real supplies also have
relatively high-frequency variation, from sources such as
load transients, noise, and pickup. These variations should
not be considered by the monitor in determining whether
a supply voltage is valid or not. The variations may cause
spurious outputs at RST, particularly if the supply voltage
is near its trip threshold.
Two techniques are used to combat spurious reset without
sacrificing threshold accuracy. First, the timeout period
helps prevent high-frequency variation whose frequency
is above 1/ tRST from appearing at the RST output.
When the voltage at VM goes below the threshold, the
RST pin asserts low. When the supply recovers past
the threshold, the reset timer starts (assuming it is not
disabled), and RST does not go high until it finishes. If
the supply becomes invalid any time during the timeout
period, the timer resets and begins again when the supply
next becomes valid.
While the reset timeout is useful at preventing toggling
of the reset output in most cases, it is not effective at
preventing nuisance resets due to short glitches (due to
load transients or other effects) on a valid supply.
To reduce sensitivity to these short glitches, the comparator
has additional anti-glitch circuitry. Any transient at the input
of the comparator needs to be of sufficient magnitude and
duration tUV before it can change the monitor state.
The combination of the reset timeout and anti-glitch circuitry prevents spurious changes in output state without
sacrificing threshold accuracy.
Adjustable Input
When the monitor threshold is configured as ADJ, the
internal comparator input is connected to the pin without
a resistive divider, and the pin is high-impedance. Thus,
any desired threshold may be chosen by attaching VM to
a tap point on an external resistive divider between the
monitored supply and ground, as shown in Figure 1.
The reference input of the comparator is controlled by the
tolerance pin. The external resistive divider should make
the voltage at VM = 0.5V when the supply is at nominal
value. The actual threshold of VM accounts for the supply tolerance of ±1.5% guaranteed over the full operating
temperature range. The resulting tolerances are –6.5%,
–11.5%, –16.5% which correspond to 0.468V, 0.443V,
0.418V repectively.
VMON
R2
–
VM
R1
+
+
–
0.5V
29156 F01
Figure 1. Setting the Trip Point Using the Adjustable Threshold
29156fa
8
LTC2915/LTC2916
APPLICATIONS INFORMATION
Typically, the user will pick a value of R1 based on acceptable current draw. Current used by the resistor divider will
be approximately
⎛ 0.5V ⎞
R1= ⎜
⎝ I ⎟⎠
RST Output Characteristics
Recommended range of R1 is 1k to 1M. Higher values
of resistance exacerbate the degradation of threshold
accuracy due to leakage currents.
If the nominal value of the supply being monitored is
VNOM, then
R2 = R1(2VNOM – 1)
Resistor tolerances must be taken into account when
determining the overall accuracy.
Selecting the Reset Timing Capacitor
The reset timeout period can be set to one of two fixed
internal timers or set with a capacitor in order to accommodate a variety of applications. Connecting a capacitor,
CRT, between the RT pin and ground sets the reset timeout
period, tRST. The following formula approximates the value
of capacitor needed for a particular timeout:
CRT = tRST • 110 [pF/ms]
For example, using a standard capacitor value of 2.2nF
would give 20ms delay.
Figure 2 shows the reset timeout period as a function of
the value of the timer capacitor.
RESET TIMEOUT PERIOD, tRST (ms)
10000
1000
The DC characteristics of the RST pull-down strength
are shown in the Typical Performance Characteristics
section. RST is an open-drain pin and thus requires an
external pull-up resistor to the logic supply. RST may be
pulled above VCC, providing the voltage limits of the pin
are observed.
The open-drain of the RST pin allows for wired-OR connection of several LTC2915/LTC2916s.
As noted in the discussion of power up and power down,
the circuits that drive RST are powered by VCC. During a
fault condition, VCC of at least 1V ensures that RST pulls
low.
Manual Reset (LTC2916 Only)
The LTC2916 includes the MR pin for applications where
a manual reset is desired. MR is internally pulled up, allowing it to interface with a push button with no external
components required. Asserting MR low when RST is high,
initiates a reset, resulting in RST being asserted low for
the set reset timeout.
Shunt Regulator
The LTC2915 and LTC2916 contain an internal 6.2V shunt
regulator on the VCC pin to allow operation from a high
voltage supply. To operate the part from a supply higher
than 5.7V, the VCC pin must have a series resistor, RCC, to
the supply. This resistor should be sized according to the
following equation:
VS(MAX ) − 5.7 V
100
5mA
10
≤ RCC ≤
VS(MIN) − 7 V
250μA
where VS(MIN) and VS(MAX) are the operating minimum
and maximum of the supply.
1
0.1
0.001
Leaving RT open with no external capacitor generates a
reset timeout of approximately 400μs. Shorting RT to VCC
generates a reset timeout of approximately 200ms.
0.01
0.1
1
10
100
RT PIN CAPACITANCE, CRT (nF)
1000
29156 F02
As an example, consider operation from an automobile
battery which might dip as low as 10V or spike to 60V. We
must then pick a resistance between 10.86k and 12k.
Figure 2. Reset Timeout Period vs RT Capacitance
29156fa
9
LTC2915/LTC2916
TYPICAL APPLICATIONS
12V Supply Monitor Powered from 12V, Utilizing
Internal Shunt Regulator with 3.3V Logic Out
12V
5V, –10% Tolerance Supply Monitor with
200ms Internal Reset Timeout
3.3V
3.3V
CBYPASS
0.1μF
RPU
10k
RCC
11k
CBYPASS
0.1μF
VCC
VCC
VCC
VCC
LTC2915
LTC2915
μP
RST
VM
5V
RST
SEL1
3.3V
GND
SEL2
SEL1
GND
29156 TA03
TOL
GND
RT
RT
3.3V
CRT
9V, –15% Tolerance Supply Monitor with 3.3V Logic Out
1V, –15% Tolerance Supply Monitor with 90ms Timeout
3.3V
9V
CBYPASS
0.1μF
R2
866k
3.3V
CBYPASS
0.1μF
RPU
10k
μP
RST
LTC2915
RST
SEL1
1V
GND
SEL2
μP
RST
VM
RST
SEL1
29156 TA04
TOL
GND
VCC
VCC
LTC2915
GND
SEL2
29156 TA05
TOL
GND
RT
RT
CRT
0.01μF
CRT
1.5V Supply Monitor with Tolerance Control for Margining,
–5% Operation with –15% Margining
1.8V, –5% Supply Monitor with Manual Reset
1.8V
RPU
10k
VCC
VCC
VM
R1
51.1k
μP
RST
RST
VM
SEL2
29156 TA02
TOL
GND
RPU
10k
3.3V
CBYPASS
0.1μF
RPU
10k
CBYPASS
0.1μF
VCC
RPU
10k
VCC
LTC2916
VM
RST
1.5V
29156 TA07
MR
MANUAL RESET
PUSHBUTTON
LTC2915
GND
SEL2
GND
VCC
RST
SEL1
10k*
VCC
μP
VM
μP
RST
RST
I/O GND
SEL1
–15% –5%
SEL2
29156 TA08
RT
GND
CRT
RT
CRT
*OPTIONAL RESISTOR RECOMMENDED TO EXTEND ESD TOLERANCE
29156fa
10
LTC2915/LTC2916
PACKAGE DESCRIPTION
TS8 Package
8-Lead Plastic TSOT-23
(Reference LTC DWG # 05-08-1637)
0.52
MAX
2.90 BSC
(NOTE 4)
0.65
REF
1.22 REF
1.4 MIN
3.85 MAX 2.62 REF
2.80 BSC
1.50 – 1.75
(NOTE 4)
PIN ONE ID
RECOMMENDED SOLDER PAD LAYOUT
PER IPC CALCULATOR
0.22 – 0.36
8 PLCS (NOTE 3)
0.65 BSC
0.80 – 0.90
0.20 BSC
0.01 – 0.10
1.00 MAX
DATUM ‘A’
0.30 – 0.50 REF
1.95 BSC
0.09 – 0.20
(NOTE 3)
TS8 TSOT-23 0802
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DRAWING NOT TO SCALE
3. DIMENSIONS ARE INCLUSIVE OF PLATING
4. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
5. MOLD FLASH SHALL NOT EXCEED 0.254mm
6. JEDEC PACKAGE REFERENCE IS MO-193
DDB Package
8-Lead Plastic DFN (3mm × 2mm)
(Reference LTC DWG # 05-08-1702 Rev B)
0.61 ±0.05
(2 SIDES)
3.00 ±0.10
(2 SIDES)
R = 0.115
TYP
5
R = 0.05
TYP
0.40 ± 0.10
8
0.70 ±0.05
2.55 ±0.05
1.15 ±0.05
PACKAGE
OUTLINE
0.25 ± 0.05
0.50 BSC
2.20 ±0.05
(2 SIDES)
PIN 1 BAR
TOP MARK
(SEE NOTE 6)
0.200 REF
RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS
2.00 ±0.10
(2 SIDES)
0.56 ± 0.05
(2 SIDES)
0.75 ±0.05
0 – 0.05
4
0.25 ± 0.05
1
PIN 1
R = 0.20 OR
0.25 × 45°
CHAMFER
(DDB8) DFN 0905 REV B
0.50 BSC
2.15 ±0.05
(2 SIDES)
BOTTOM VIEW—EXPOSED PAD
NOTE:
1. DRAWING CONFORMS TO VERSION (WECD-1) IN JEDEC PACKAGE OUTLINE M0-229
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
29156fa
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.
11
LTC2915/LTC2916
TYPICAL APPLICATION
Dual Supply Monitor (1.8V and 12V) with Manual Reset and 200ms Reset Timeout
1.8V
CBYPASS
0.1μF
RPU
10k
VCC
LTC2916
RST
VM
12V
VM
SEL1
SEL1
SEL2
SEL2
MR
MANUAL RESET
PUSHBUTTON
1.8V
GND
VCC
VCC
LTC2915
RT
1.8V
TOL
GND
μP
RST
RST
GND
29156 TA10
RT
1.8V
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
LTC690
5V Supply Monitor, Watchdog Timer and Battery Backup
4.65V Threshold
LTC694-3.3
3.3V Supply Monitor, Watchdog Timer and Battery Backup
2.9V Threshold
LTC1232
5V Supply Monitor, Watchdog Timer and Push-Button Reset
4.37V/4.62V Threshold
LTC1326
Micro Power Precision Triple Supply Monitor
4.725V, 2.363V, 3.118V, 1V Threshold (±0.75%)
LTC1726
Micro Power Triple Supply Monitor for 2.5V/5V, 3.3V and ADJ Adjustable RESET and Watchdog Time-Outs
LTC1727
Micro Power Triple Supply Monitor with Open-Drain Reset
Individual Monitor Outputs in MSOP
LTC1728
Micro Power Triple Supply Monitor with Open-Drain Reset
5-Lead SOT-23 Package
LTC1985-1.8
Micro Power Triple Supply Monitor with Push-Pull Reset
5-Lead SOT-23 Package
LTC2900
Programmable Quad Supply Monitor
Adjustable RESET, 10-Lead MSOP and 3mm × 3mm 10-Lead DFN
LTC2901
Programmable Quad Supply Monitor
Adjustable RESET and Watchdog Timer, 16-Lead SSOP Package
LTC2902
Programmable Quad Supply Monitor
Adjustable RESET and Tolerance, 16-Lead SSOP Package, Margining
LTC2903
Precision Quad Supply Monitor
6-Lead SOT-23 Package, Ultra Low Voltage Reset
LTC2904/LTC2905
3-State Programmable Precision Dual Supply Monitor
Adjustable RESET and Tolerance, 8-Lead SOT-23 Package
LTC2906
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable
Separate VCC Pin, RST/RST Outputs
LTC2907
Precision Dual Supply Monitor 1 Selectable and 1 Adjustable
Separate VCC Pin, Adjustable Reset Timer
LTC2908
Precision Six Supply Monitor (Four Fixed and 2 Adjustable)
8-Lead SOT-23 and DDB Packages
LTC2909
Precision Triple/Dual Input UV, OV Monitor
2 ADJ Inputs, Monitors Negative Voltages
LTC2910
Octal Positive/Negative Voltage Monitor
16-Lead SSOP and 5mm × 3mm DFN Packages
LTC2912
Single UV/OV Voltage Monitor, Adjustable UV and OV Trip
Values
8-Lead TSOT and 3mm × 2mm DFN Packages
LTC2913
Dual UV/OV Voltage Monitor
10-Lead MOSP and 3mm × 3mm DFN Packages
LTC2914
Qual UV/OV Positive/Negative Voltage Monitor
16-Lead SSOP and 5mm × 3mm DFN Packages
29156fa
12 Linear Technology Corporation
LT 0108 REV A • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408) 432-1900 ● FAX: (408) 434-0507
●
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