MAX1749 Просмотр технического описания (PDF) - Maxim Integrated
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MAX1749 Datasheet PDF : 8 Pages
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SOT23 Vibrator Motor Driver
______________________________________________________________Pin Description
PIN NAME
FUNCTION
1
ON
Active-High On/Off Input. Apply a logic high to deliver power to the load. Apply a logic low to disconnect the
load and reduce the supply current to 0.1nA.
2
GND
Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board ground plane to max-
imize thermal dissipation.
3
IN
Regulator Input. Supply voltage can range from +2.5V to +6.5V. Bypass with 1µF to GND (see Capacitor
Selection and Regulator Stability).
4
OUT
Regulator Output. Fixed 1.25V or adjustable from 1.25V to VIN. Sources up to 120mA. Bypass with a 1µF,
<0.2Ω typical ESR capacitor to GND.
5
SET
Feedback Input for Setting the Output Voltage. Connect to OUT for 1.25V regulated output (see Output
Voltage Selection). Connect to an external resistor-divider for adjustable-output operation.
Detailed Description
The MAX1749 is a low-quiescent-current, vibrator motor dri-
ver designed for battery-powered wireless handsets and
pagers. The device supplies an adjustable +1.25V to +6.5V
output for load currents up to 120mA. The MAX1749 allows
for a constant vibration force while operating from a +2.5V
to +6.5V input voltage range.
The 1.25V bandgap reference is connected to the error
amplifier’s inverting input. The error amplifier compares this
reference with the feedback voltage and amplifies the differ-
ence. The MOSFET driver reads the error signal and
applies the appropriate drive to the p-channel pass transis-
tor. If the feedback voltage is lower than the reference volt-
age, the pass-transistor gate is pulled lower than the
reference, allowing more current to flow and increasing the
output voltage. If the feedback voltage is too high, the pass-
transistor gate is pulled-up, allowing less current to flow to
the output. The output voltage is fed back to SET either
directly for a 1.25V fixed output or through an external resis-
tor-divider for an adjustable +1.25V to VIN output. Additional
blocks include a current limiter, reverse battery protection, a
thermal sensor, and ON/OFF logic.
Internal P-Channel Pass Transistor
The MAX1749 features a 1.1Ω typical P-channel MOS-
FET pass transistor. This provides several advantages
over similar designs using PNP pass transistors, includ-
ing longer battery life.
IN
REVERSE
BATTERY
ON PROTECTION
MAX1749
ON/OFF
LOGIC
ERROR
AMP
MOS DRIVER
WITH ILIMIT
P
OUT
SET
THERMAL
SENSOR
1.25V
REF
GND
Figure 1. Functional Diagram
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