LM8500HVA9 National Semiconductor, LM8500HVA9 Datasheet - Page 15

• Manufacturer Part Number: LM8500HVA9
• Description: IC TOUCHSCREEN CONTROLLER 44PLCC
• Manufacturer: National Semiconductor
• Type: Resistiver

Specifications of LM8500HVA9

• Touch Panel Interface: 4-Wire
• Number Of Inputs/keys: 1 TSC
• Resolution (bits): 10 b
• Data Interface: UART
• Data Rate/sampling Rate (sps, Bps): 38.4k
• Voltage - Supply: 2.7 V ~ 5.5 V
• Current - Supply: 11.5mA
• Operating Temperature: 0°C ~ 70°C
• Mounting Type: Surface Mount
• Package / Case: 44-PLCC
• Voltage Supply Source: Single Supply
• For Use With: LM8500-REF-01 - BOARD EVALUATION LM8500
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Sampling Rate (per Second): -
• Other names: *LM8500HVA9

13.0 Brownout Reset
The internal reset will not be turned off until t
to zero. The internal reset will perform the same functions as
external reset. The device is guaranteed to operate at the
specified frequency down to the specified brownout voltage.
After the underflow, the logic is designed such that no addi-
tional internal resets occur as long as V
the brownout voltage.
The device is relatively immune to short duration negative
going V
power supply voltage is essential for proper brownout func-
tionality. Power supply decoupling is vital even in battery
powered systems.
There are two optional brownout voltages. The part numbers
for the two versions of this device are:
LM8500, V
LM8300, V
Refer to the device specifications for the actual V
ages.
High brownout voltage devices are guaranteed to operate at
10MHz down to the high brownout voltage. Low brownout
voltage devices are guaranteed to operate at 3.33MHz down
to the low brownout voltage. Low brownout voltage devices
are not guaranteed to operate at 10MHz down to the low
brownout voltage.
Under no circumstances should the RESET pin be allowed
to float. The RESET input may be connected to an external
pull-up resistor to V
output of the brownout reset detector will always preset t
CC
bor
bor
transients (glitches). Proper filtering of the V
= high voltage range.
= low voltage range.
CC
or to other external circuitry. The
(Continued)
CC
FIGURE 4. Brownout Reset Operation
remains above
id
counts down
bor
volt-
id
CC
to
15
a value between 120-128µs for the LM8500 and 360-384µs
for the LM8300. At this time, the internal reset will be gener-
ated.
The device has a built in watchdog monitoring module to
prevent runaway code. To use the watchdog feature, the
WD_OUT pin must be connected to the RESET pin. The
WD_OUT pin has an internal weak pull-up so that, when the
WD_OUT pin is connected to the RESET pin, the RESET pin
does not require an external pull-up resistor to V
14.0 Calibration
The device supports two, five, and thirteen point calibration.
If desired, the calibration points can be stored internally in
the non-volatile storage element. During calibration time, the
device has the unique ability to check if the calibration points
make sense. For instance, if the desired calibration point
was to be at the upper left hand corner, but by accident, the
actual point detected was at the lower right hand corner, the
device will reject this point. This ensures the calibration
process is not performed incorrectly.
The calibration checking, can be enabled or disabled. If the
calibration checking is enabled, the controller will always
check the current calibration point being done against the
theoretical point and determine if the value is within
the raw A/D values. If this option is desired, the touch screen
driver must perform the calibration according to the calibra-
tion mapping for the two, five, and thirteen points as shown
in Figure 5, Figure 6, and Figure 7, respectively. The theo-
retical values for the two, five, and thirteen points are shown
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