TSM9117-TSM9120
Output Stage Circuitry
voltage reference is typically 200kꢀ, preventing the
reference from driving large loads. The reference is
Many conventional analog comparators can draw
orders of magnitude higher supply current when
switching. Because of this behavior, additional
power supply bypass capacitance may be required
to provide additional charge storage during
switching. The design of the TSM9117–TSM9120’s
rail-to-rail output stage implements a technique that
virtually eliminates supply-current surges when
output transitions occur. As shown on Page 5 of the
Typical Operating Characteristics, the supply-current
change as a function of output transition frequency
exhibited by this analog comparator family is very
small. Material benefits of this attribute to battery-
power applications is the increase in operating time
and in reducing the size of power-supply filter
capacitors.
Figure 1: TSM9117 & TSM9118 Internal VREF
Output Equivalent Circuit
TSM9117/9118’s Internal +1.252V VREF
The TSM9117 and the TSM9118’s internal +1.252V
voltage reference exhibits a typical temperature
coefficient of 100ppm/°C over the full -40°C to
+85°C temperature range. An equivalent circuit for
the reference section is illustrated in Figure 1. Since
the output impedance of the voltage reference
typically 200kꢀ, its output can be bypassed with a
low-leakage capacitor and is stable for any
capacitive load. An external buffer – such as the
TS1001 – can be used to buffer the voltage
reference output for higher output current drive or to
reduce reference output impedance.
APPLICATIONS INFORMATION
feedback, many analog comparators often break into
oscillation within their linear region of operation
especially when the applied differential input voltage
approaches 0V (zero volt). Externally-introduced
Low-Voltage, Low-Power Operation
Designed specifically for low-power applications, the
TSM9117–TSM9120 comparators are an excellent
choice. Under nominal conditions, approximate
operating times for this analog comparator family is
illustrated in Table 1 for a number of battery types
and their charge capacities.
hysteresis is
a
well-established technique to
stabilizing analog comparator behavior and requires
external components. As shown in Figure 2, adding
comparator hysteresis creates two trip points: VTHR
(for the rising input voltage) and VTHF (for the falling
input voltage). The hysteresis band (VHB) is defined
as the voltage difference between the two trip points.
When a comparator’s input voltages are equal,
Internal Hysteresis
As a result of circuit noise or unintended parasitic
Table 1: Battery Applications using the TSM9117- TSM9120
TSM9117/TSM9118
OPERATING TIME
(hrs)
TSM9119/TSM9120
OPERATING TIME
(hrs)
VFRESH
(V)
CAPACITY, AA
SIZE (mA-h)
BATTERY TYPE
RECHARGEABLE
VEND-OF-LIFE (V)
Alkaline (2 Cells)
No
3.0
2.4
3.5
2.4
1.8
1.8
2.7
1.8
2000
2.5 x 106
5 x 106
1.875 x 106
2.5 x 106
2.5 x 106
Nickel-Cadmium
(2 Cells)
Yes
Yes
Yes
750
937,500
Lithium-Ion (1 Cell)
1000
1.25 x 106
1.25 x 106
Nickel-Metal-
Hydride (2 Cells)
1000
Page 12
TSM9117_20DS r1p0
RTFDS
TOUCHSTONE [ TOUCHSTONE SEMICONDUCTOR INC ]
