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PDF TSM917 Data sheet ( Hoja de datos )
| Número de pieza | TSM917 | |
| Descripción | 1.8V Nanopower Comparator | |
| Fabricantes | Touchstone Semiconductor | |
| Logotipo |  |
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TSM917
1.8V Nanopower Comparator with Internal 1.245V Reference
FEATURES
♦ Second-source for MAX917
♦ Guaranteed to Operate Down to +1.8V
♦ Ultra-Low Supply Current: 750nA
♦ Internal 1.245V ±1.5% Reference
♦ Input Voltage Range Extends 200mV Outside-the-Rails
♦ No Phase Reversal for Overdriven Inputs
♦ Push-pull Output
♦ Crowbar-Current-Free Switching
♦ Internal Hysteresis for Clean Switching
♦ 5-pin SOT23 and 8-pin SOIC Packaging
APPLICATIONS
2-Cell Battery Monitoring/Management
Medical Instruments
Threshold Detectors/Discriminators
Sensing at Ground or Supply Line
Ultra-Low-Power Systems
Mobile Communications
Telemetry and Remote Systems
DESCRIPTION
The TSM917 nanopower analog comparator is
electrically and form-factor identical to the MAX917
analog comparator. Ideally suited for all 2-cell battery-
management/monitoring applications, this 5-pin
SOT23 analog comparator guarantees +1.8V
operation, draws very little supply current, and has a
robust input stage that can tolerate input voltages
beyond its power supply. The TSM917 draws 750nA
of supply current and includes an on-board 1.245V
±1.5% reference.
The TSM917’s push-push output drivers were
designed to drive 8mA loads from one supply rail to
the other supply rail. The TSM917 is also available in
an 8-pin SOIC package.
TYPICAL APPLICATION CIRCUIT
The Touchstone Semiconductor logo is a registered
trademark of Touchstone Semiconductor, Incorporated.
Page 1
© 2011 Touchstone Semiconductor, Inc. All rights reserved.
1 page  
TSM917
TYPICAL PERFORMANCE CHARACTERISTICS
VCC = +5V; VEE = 0V; CL = 15pF; VOVERDRIVE = 100mV; TA = +25°C, unless otherwise noted.
Output Voltage High
vs Source Current and Temperature
Short-Circuit Sink Current vs Temperature
0.6 120
0.5
TA = +85°C
0.4
100
VCC =+5V
80
0.3 TA = +25°C
0.2
TA = -40°C
0.1
60
VCC =+3V
40
20 VCC =+1.8V
0
0
4 8 12 16
SOURCE CURRENT- mA
20
0
-40
-15 10 35 60
TEMPERATURE - °C
85
Short-Circuit Source Current vs Temperature
140
120
100
VCC =+5V
80
60
VCC =+3V
40
20
0
-40
VCC =+1.8V
-15 10 35 60
TEMPERATURE - °C
85
Offset Voltage vs Temperature
2.6
2.4
2.2 VCC =+1.8V, 3V
2.0
1.8
1.6
1.4
-40
VCC =+5V
-15 10 35 60
TEMPERATURE - °C
85
Hysteresis Voltage vs Temperature
5.5
5
4.5
4
3.5
3
2.5
-40
-15 10 35 60
TEMPERATURE - °C
TSM917DS r1p0
85
Reference Voltage vs Temperature
1.246
1.245
VCC =+1.8V
1.244
1.243
VCC =+3V
1.242
VCC =+5V
1.241
-40
-15 10 35 60
TEMPERATURE - °C
85
Page 5
RTFDS
5 Page 
move quickly past the other input, moving the input
out of the region where oscillation occurs. Figure 2
illustrates the case in which an IN- input is a fixed
voltage and an IN+ is varied. If the input signals
were reversed, the figure would be the same with an
inverted output. To save cost and external pcb area,
an internal 4mV hysteresis circuit was added to the
TSM917.
Figure 2: TSM917’s Threshold Hysteresis Band
Adding Hysteresis to the TSM917
The TSM917 exhibits an internal hysteresis band
(VHB) of 4mV. Additional hysteresis can be
generated with three external resistors using positive
feedbackas shown in Figure 3. Unfortunately, this
method also reduces the hysteresis response time.
The design procedure below can be used to
calculate resistor values.
Figure 3: Using Three Resistors Introduces Additional
Hysteresis in the TSM917.
1) Setting R2. As the leakage current at the IN
pin is under 2nA, the current through R2
should be at least 0.2μA to minimize offset
voltage errors caused by the input leakage
current. The current through R2 at the trip
TSM917DS r1p0
TSM917
point is (VREF - VOUT)/R2.
In solving for R2, there are two formulas –
one each for the two possible output states:
R2 = VREF/IR2
or
R2 = (VCC - VREF)/IR2
From the results of the two formulae, the
smaller of the two resulting resistor values is
chosen. For example, when using the
TSM917 (VREF = 1.245V) at a VCC = 3.3V
and if IR2 = 0.2μA is chosen, then the
formulae above produce two resistor values:
6.23MΩ and 10.24MΩ - the 6.2MΩ standard
value for R2 is selected.
2) Next, the desired hysteresis band (VHYSB) is
set. In this example, VHYSB is set to 100mV.
3) Resistor R1 is calculated according to the
following equation:
R1 = R2 x (VHB/VCC)
and substituting the values selected in 1)
and 2) above yields:
R1 = 6.2MΩ x (100mV/3.3V) = 187.88kΩ
The 187kΩ standard value for R1 is
selected.
4) The trip point for VIN rising (VTHR) is chosen
such that VTHR > VREF x (R1 + R2)/R2 (where
VTHF is the trip point for VIN falling). This is
the threshold voltage at which the
comparator switches its output from low to
high as VIN rises above the trip point. In this
example, VTHR is set to 3V.
5) With the VTHR from Step 4 above, resistor R3
is then computed as follows:
R3 = 1/[VTHR/(VREF x R1) - (1/R1) - (1/R2)]
R3 = 1/[3V/(1.245V x 187kΩ) - (1/187kΩ)
- (1/6.2MΩ)] = 135.56kΩ
In this example, a 137kΩ, 1% standard
value resistor is selected for R3.
Page 11
RTFDS
11 Page | ||
| Páginas | Total 14 Páginas | |
| PDF Descargar | [ Datasheet TSM917.PDF ] | |
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