MAX907C/D MAXIM [Maxim Integrated Products], MAX907C/D Datasheet - Page 9

• Manufacturer Part Number: MAX907C/D
• Description: Single/Dual/Quad High-Speed, Ultra Low-Power, Single-Supply TTL Comparators
• Manufacturer: MAXIM [Maxim Integrated Products]

Figure 1. Input and Output Waveforms, Noninverting Input
Varied
Because of the MAX907/MAX908/MAX909’s high gain
bandwidth, special precautions must be taken to real-
ize the full high-speed capability. A printed circuit
board with a good, low-inductance ground plane is
mandatory. Place the decoupling capacitor (a 0.1µF
ceramic capacitor is a good choice) as close to V+ as
possible. Pay close attention to the decoupling capaci-
tor’s bandwidth, keeping leads short. Short lead
lengths on the inputs and outputs are also essential to
avoid unwanted parasitic feedback around the com-
parators. Solder the device directly to the printed cir-
cuit board instead of using a socket.
The inputs to the MAX907/MAX908/MAX909 may be
driven beyond the voltage limits given in the Absolute
Maximum Ratings , as long as the current flowing into
the device is limited to 25mA. However, if the inputs
are overdriven, the output may be inverted. The addi-
tion of an external diode prevents this inversion by limit-
ing the input voltage to 200mV to 300mV below ground
(see Figure 3).
__________Applications Information
Single/Dual/Quad High-Speed, Ultra Low-Power,
V
V
COMPARATOR
V
TRIP+
HYST
TRIP-
OUTPUT
_______________________________________________________________________________________
Overdriving the Inputs
V
IN+
Circuit Layout
V
V
OS
IN-
Single-Supply TTL Comparators
=
= 0V
V
TRIP+
V
V
OH
OL
2
+ V
TRIP-
Figure 2. MAX909 Timing Diagram
Figure 4's circuit allows reception of infrared data. The
MAX403 converts the photodiode current to a voltage,
and the MAX907 determines whether the amplifier output
is high enough to be called a “1”. The current consump-
tion of this circuit is minimal: The MAX403 and MAX907
require typically 250µA and 700µA, respectively.
DIFFERENTIAL
VOLTAGE
OUTPUT
OUTPUT
(QOUT)
(QOUT)
INPUT
Battery-Operated Infrared Data Link
LE
1.4V
1.4V
1.4V
V
V
V
V
V
3V
OH
OH
OS
OL
OL
0
COMPARE
t
s
V
V
IN
OD
t
h
t
PD
LATCH
+
t
SKEW
9