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19-1455; Rev 1; 6/99
SOT23 Vibrator Motor Driver
General Description
The MAX1749 allows for a constant vibration force while operating from a +2.5V to +6.5V input range and delivering up to 120mA. A PMOS pass transistor allows the 80A supply current to remain independent of the load. The output voltage can be adjusted from +1.25V to VIN with an external resistor-divider. When turned off (ON = low), the MAX1749 supply current drops to 1A (max) to minimize battery drain. Other features include short-circuit protection, thermal shutdown protection, and reverse battery protection. The MAX1749 is available in a 5-pin SOT23 package.
____________________________Features
o Fixed 1.25V or Adjustable (1.25V to 6.5V) Output o Low Cost o Thermal Overload Protection o Output Current Limit o Reverse Battery Protection o Low 0.1nA Off Supply Current o Low 80A Full-Load Supply Current
MAX1749
________________________Applications
Wireless Handset Vibrator Motor Drivers Pager Vibrator Motor Drivers
PART MAX1749EUK-T
Ordering Information
TEMP. RANGE -40C to +85C PINPACKAGE 5 SOT23 TOP MARK ADIX
Typical Operating Circuit
TOP VIEW
2.5V TO 6.5V IN CIN 1F ON BATTERY OFF GND ON OUT COUT 1F 1.25V UP TO 120mA
Pin Configuration
ON 1
5
SET
MAX1749
SET
GND 2
MAX1749
IN 3
4
OUT
SOT23-5
________________________________________________________________ Maxim Integrated Products
1
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SOT23 Vibrator Motor Driver MAX1749
ABSOLUTE MAXIMUM RATINGS
IN to GND ....................................................................-7V to +7V Output Short-Circuit Duration ............................................Infinite SET to GND ..............................................................-0.3V to +7V ON to GND ..................................................................-7V to +7V ON to IN....................................................................-7V to +0.3V OUT to GND ................................................-0.3V to (VIN + 0.3V) Continuous Power Dissipation (TA = +70C) SOT23-5 (derate 7.1mW/C above +70C) .................571mW Operating Temperature Range ...........................-40C to +85C Junction Temperature ......................................................+150C JA ...............................................................................+140C/W Storage Temperature Range .............................-65C to +150C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
ELECTRICAL CHARACTERISTICS
(VIN = +3.6V, TA = -40C to +85C, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Input Voltage Output Voltage Maximum Output Current Current Limit (Note 2) Ground Pin Current Off Supply Current ON INPUT ON Input High Threshold ON Input Low Threshold ON Input Bias Current SET INPUT SET Input Leakage Current THERMAL PROTECTION Thermal Shutdown Temperature Thermal Shutdown Hysteresis TSHDN TSHDN 170 20 C C ISET VSET = 1.4V TA = +25C TA = +85C 0.03 0.5 10 nA VIH VIL ION ON = IN TA = +25C TA = +85C 0 0.05 2.0 0.4 100 V V nA ILIM IQ IOFF VOUT = VON = GND TA = +25C TA = +85C SYMBOL VIN VOUT 0.1mA IOUT 50mA, SET = OUT CONDITIONS MIN 2.5 1.13 120 280 80 0.0001 0.02 200 1 1.25 TYP MAX 6.5 1.37 UNITS V V mA mA A A
Note 1: Limits are 100% production tested at TA = +25C. Limits over the operating temperature range are guaranteed through correlation using Statistical Quality Control (SQC) methods. Note 2: Not tested. For design purposes, the current limit should be considered 120mA minimum to 420mA maximum.
2
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SOT23 Vibrator Motor Driver MAX1749
__________________________________________Typical Operating Characteristics
(VIN = +3.6V, SET = OUT, CIN = 1F, COUT = 1F, TA = +25C, unless otherwise noted.)
OUTPUT VOLTAGE vs. LOAD CURRENT
MAX1749 TOC01
SUPPLY CURRENT vs. LOAD CURRENT
90 80 SUPPLY CURRENT (A) 70 60 50 40 30 20 10
MAX1749toc02
OUTPUT VOLTAGE vs. INPUT VOLTAGE
MAX1749toc03
1.27 1.26 OUTPUT VOLTAGE (V) 1.25 1.24 1.23 1.22 1.21 0 20 40 60 80 100
100
1.4 1.2 OUTPUT VOLTAGE (V) 1.0 0.8 0.6 0.4 0.2 0
0 120 0 20 40 60 80 100 120 LOAD CURRENT (mA) LOAD CURRENT (mA)
0
1
2
3
4
5
6
INPUT VOLTAGE (V)
SUPPLY CURRENT vs. INPUT VOLTAGE
MAX1749 toc04
OUTPUT VOLTAGE vs. TEMPERATURE
ILOAD = 50mA 1.27 OUTPUT VOLTAGE (V) 1.26 1.25 1.24 1.23 1.22 1.21
MAX1749 toc05
120 100 SUPPLY CURRENT (A) 80 60 ILOAD = 0 40 20 0 0 1 2 3 4 5 6 INPUT VOLTAGE (V) ILOAD = 50mA
1.28
-40
-15
10
35
60
85
TEMPERATURE (C)
SUPPLY CURRENT vs. TEMPERATURE
MAX1749 toc06
REGION OF STABLE COUT ESR vs. LOAD CURRENT
MAX1749 toc08
100 90 80 SUPPLY CURRENT (A) 70 60 50 40 30 20 10 0 -40 -20 0 20 40 60 80 ILOAD = 50mA
10
COUT ESR ()
1
STABLE REGION 0.1
0.01 100 0 20 40 60 80 100 120 TEMPERATURE (C) LOAD CURRENT (mA)
_______________________________________________________________________________________
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SOT23 Vibrator Motor Driver MAX1749
Typical Operating Characteristics (continued)
(VIN = +3.6V, SET = OUT, CIN = 1F, COUT = 1F, TA = +25C, unless otherwise noted.)
LINE-TRANSIENT RESPONSE
MAX1749 toc09
LOAD-TRANSIENT RESPONSE
1.25V
1.24V
MAX1749 toc10
1.25V
1.24V
VOUT
VOUT
1.23V
1.23V
4.6V VIN 3.6V 50s/div ILOAD = 50mA, CIN = 10F, VOUT = AC-COUPLED 10s/div ILOAD = 0 to 50mA, CIN = 10F, VOUT = AC-COUPLED ILOAD 20mA/div
ON/OFF WAVEFORM (VIN = 5.0V)
MAX1749 toc13
ON/OFF WAVEFORM (VIN = 3.6V)
2V 0V 1V VOUT 0V 200mA ILOAD ILOAD 0mA 100ms/div VIBRATOR MOTOR LOAD VOUT
MAX1749 toc14
4V
5V 0V 1V 0V 200mA
VON
VON
0mA 100ms/div VIBRATOR MOTOR LOAD
4
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SOT23 Vibrator Motor Driver
______________________________________________________________Pin Description
PIN 1 2 3 4 5 NAME ON GND IN OUT SET FUNCTION 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. Ground. This pin also functions as a heatsink. Solder to large pads or the circuit board ground plane to maximize thermal dissipation. Regulator Input. Supply voltage can range from +2.5V to +6.5V. Bypass with 1F to GND (see Capacitor Selection and Regulator Stability). Regulator Output. Fixed 1.25V or adjustable from 1.25V to VIN. Sources up to 120mA. Bypass with a 1F, <0.2 typical ESR capacitor to GND. 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.
MAX1749
Detailed Description
The MAX1749 is a low-quiescent-current, vibrator motor driver 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 difference. The MOSFET driver reads the error signal and applies the appropriate drive to the p-channel pass transistor. If the feedback voltage is lower than the reference voltage, the pass-transistor gate is pulled lower than the
IN ON REVERSE BATTERY PROTECTION
reference, allowing more current to flow and increasing the output voltage. If the feedback voltage is too high, the passtransistor 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 resistor-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 1.1 typical P-channel MOSFET pass transistor. This provides several advantages over similar designs using PNP pass transistors, including longer battery life.
ERROR AMP
MOS DRIVER WITH ILIMIT
P
MAX1749
ON/OFF LOGIC
OUT SET
THERMAL SENSOR
1.25V REF
GND
Figure 1. Functional Diagram
_______________________________________________________________________________________ 5
SOT23 Vibrator Motor Driver MAX1749
the regulator turns off; however, inertial energy in the motor exhibits a slow output voltage decline. The MAX1749 is designed to withstand this condition with no negative effects.
IN
OUT
OUTPUT VOLTAGE
ON CIN BATTERY 1F ON OFF
MAX1749
SET GND
Current Limit
R1
R2
COUT 1F
VIBRATOR
The MAX1749 includes a current limiter that monitors and controls the pass transistor's gate voltage, estimating the output current and limiting it to about 280mA. For design purposes, the current limit should be considered 120mA (min) to 420mA (max). The output can be shorted to ground for an infinite time period without damaging the part.
Thermal-Overload Protection
Figure 2. Adjustable Output Using External Feedback Resistors
The P-channel MOSFET requires no base drive current, which reduces quiescent current considerably. PNPbased regulators waste considerable amounts of base current under large loads. The MAX1749 does not suffer from these problems and consumes only 80A of quiescent current independent of the load (see Typical Operating Characteristics).
Thermal-overload protection limits total power dissipation in the MAX1749. When the junction temperature exceeds TJ = +170C, the thermal sensor sends a signal to the ON/ OFF logic, turning off the pass transistor and allowing the IC to cool. The thermal sensor will turn the pass transistor on again after the IC's junction temperature cools by typically 20C, resulting in a pulsed output during continuous thermal-overload conditions.
Operating Region and Power Dissipation
Maximum power dissipation of the MAX1749 depends on the thermal resistance of the case and circuit board, the temperature difference between the die junction and ambient air, and the rate of air flow. The power dissipation across the device is P = IOUT (VIN - VOUT). The resulting maximum power dissipation is: PMAX = (TJ - TA) / JA where (TJ - TA) is the temperature difference between the MAX1749 die junction and the surrounding air, and JA is +140C/W. GND performs the dual function of providing an electrical connection to ground and channeling heat away. Connect GND to a large pad or ground plane.
Output Voltage Selection
To select the preset 1.25V output, connect OUT directly to SET. To adjust the output (1.25V to 6.5V), use two external resistors connected as a voltage divider to SET (Figure 2). The output voltage is set by the following equation: VOUT = VSET (1 + R1 / R2) where VSET = 1.25V. To simplify resistor selection: V R1 = R2 OUT VSET - 1
Reverse Battery Protection
The MAX1749 has a unique protection scheme that limits the reverse supply current to less than 1mA when either VIN or VON falls below ground. The circuitry monitors the polarity of these two pins, disconnecting the internal circuitry and parasitic diodes when the battery is reversed. This feature prevents the device from overheating and damaging the battery.
Choose R2 = 100k to optimize power consumption, accuracy, and high-frequency power-supply rejection. The total current through the external resistive feedback and load should not be less than 10A.
O ON/OFF
Drive ON high to provide power to the load. Drive ON low to disable power to the load and reduce the supply current to typically 0.1nA (1A max). Refer to the ON/OFF waveforms in the Typical Operating Characteristics. When ON goes high, output current rises to the current limit until VOUT reaches regulation. While in regulation, the output current drops to a lower value sufficient to maintain motor speed. When ON goes low,
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VIN > 5.5V Minimum Load Current When operating the MAX1749 with an input voltage above 5.5V, the minimum current through the external feedback resistors and load must be 30A.
_______________________________________________________________________________________
SOT23 Vibrator Motor Driver
Capacitor Selection and _________________Regulator Stability
Use a 1F capacitor on the input and a 1F capacitor on the output of the MAX1749. A higher-value input capacitor (10F) may be necessary if large, fast transients are anticipated and the device is located several inches from the power source. Improve load-transient response and stability by using larger output capacitors. For stable operation over the full temperature range with load currents up to 120mA, use a 1F min capacitor (ESR < 0.2).
Chip Information
TRANSISTOR COUNT: 148
MAX1749
________________________________________________________Package Information
SOT5L.EPS
_______________________________________________________________________________________
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SOT23 Vibrator Motor Driver MAX1749
NOTES
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
8 _____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600 (c) 1999 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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