Toshiba 27WLT56B, Service Manual

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52
27” TFT TV Service Manual 05/09/2005
13.10.
MAX809
13.10.1. 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.
13.10.2. 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
13.10.3. Pin Description