Teac TFT IDTV, Service Manual

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45
22” TFT TV Service Manual 13/10/2004
12.10. MAX809
12.10.1. General Description
The MAX803/MAX809/MAX810 are microprocessor (µP) supervisory circuits used to monitor the power
supplies in µP and digital systems. They provide excellent circuit reliability and low cost by eliminating
external components and adjustments when used with +5V, +3.3V,+3.0V, or +2.5V powered circuits.
These circuits perform a single function: they assert a reset signal whenever the V
CC
supply voltage
declines below a preset threshold, keeping it asserted for at least 140ms after V
CC
has risen above the
reset threshold. Reset thresholds suitable for operation with a variety of supply voltages are available. The
MAX803 has an open-drain output stage, while the MAX809/MAX810 have push-pull outputs. The
MAX803’s open-drain RESET output requires a pull-up resistor that can be connected to a voltage higher
than V
CC
. The MAX803/MAX809 have an active-low RESET output, while the MAX810 has an active-high
RESET output. The reset comparator is designed to ignore fast transients on V
CC
, and the outputs are
guaranteed to be in the correct logic state for V
CC
down to 1V. Low supply current makes the
MAX803/MAX809/MAX810 ideal for use in portable equipment. The MAX803 is available in a 3-pin SC70
package, and the MAX809/MAX810 are available in 3-pin SC70 or SOT23 packages.
12.10.2. Features
•
1 Precision Monitoring of +2.5V, +3V, +3.3V, and +5V Power-Supply Voltages
•
Fully Specified Over Temperature
•
Available in Three Output Configurations
Open-Drain RESET Output (MAX803)
Push-Pull RESET Output (MAX809)
Push-Pull RESET Output (MAX810)
•
140ms min Power-On Reset Pulse Width
•
12µA Supply Current
•
Guaranteed Reset Valid to V
CC
= +1V
•
Power Supply Transient Immunity
•
No External Components
•
3-Pin SC70 and SOT23 Packages
12.10.3. Pin Description