● Accurately Monitors External Thermistor Temperature
● 3.0V to 5.5V Operating Voltage Range
● -40°C to +125°C Operating Temperature Range
Applications
●
●
●
●
Consumer Equipment
Communications Equipment
Computing Equipment
Industrial Equipment
Ordering Information
appears at end of data sheet.
Typical Application Circuits
2-WIRE FAN-SPEED CONTROLLER
V
DD
4-WIRE FAN-SPEED CONTROLLER
V
DD
R
ST
R
D1
C
B
R
B
V
DD
SENSE
D0
FREQ
C
F
R
ST
VFAN
R
D1
C
B
R
B
V
DD
SENSE
D0
FREQ
C
F
MAX31740
DMIN
R
D2
GND
PWM_OUT
SLOPE
R
SLOPE
MAX31740
N
DMIN
R
D2
GND
PWM_OUT
SLOPE
R
SLOPE
VFAN
TACH OR
LOCKED
ROTOR
33Hz
25kHz
For related parts and recommended products to use with this part, refer to
www.maximintegrated.com/MAX31740.related.
19-6697; Rev 0; 5/13
MAX31740
Ultra-Simple Fan-Speed Controller
Absolute Maximum Ratings
(All voltages relative to ground.)
Voltage Range on V
DD ..............................................
-0.3V to +6.0V
Voltage Range on Any Non-Power Pin
....
-0.3V to (V
DD
+ 0.3V)
Operating Temperature Range
.........................
-40°C to +125°C
Storage Temperature Range
............................
-55°C to +125°C
Junction Temperature Maximum .....................................+150°C
Soldering Temperature (reflow)
.......................................+260°C
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.
Package Thermal Characteristics (Note 1)
TDFN
Junction-to-Ambient Thermal Resistance (θ
JA
)
..........60°C/W
Junction-to-Case Thermal Resistance (θ
JC
)
...............11°C/W
Note 1:
Package thermal resistances were obtained using the method described in JEDEC specification JESD51-7, using a four-layer
board. For detailed information on package thermal considerations, refer to
www.maximintegrated.com/thermal-tutorial.
Recommended Operating Conditions
(T
A
= -40°C to +125°C, unless otherwise noted.) (Note 2)
PARAMETER
Supply Voltage
Logic 1 (D0)
Logic 0 (D0)
SYMBOL
V
DD
V
IH
V
IL
CONDITIONS
MIN
3.0
V
DD
x 0.7
-0.3
TYP
3.3
MAX
5.5
V
DD
+ 0.3
V
DD
x 0.3
UNITS
V
V
V
Electrical Characteristics
(V
DD
= V
DDMIN
to V
DDMAX
, T
A
= -40°C to +125°C, unless otherwise noted.) (Notes 2, 3)
PARAMETER
Supply Current (Note 4)
PWM Start Voltage (Note 5)
Input Bias Current (SENSE)
Internal DO Pulldown Resistor
Internal SLOPE Feedback
Resistance (Note 6)
Sawtooth Peak Voltage Offset
(Note 7)
Sawtooth Peak Voltage
R
SLOPE
Capacitive Load
(Note 8)
PWM Output Low
PWM Output High
PWM Frequency
SYMBOL
I
DD
V
START
I
BIAS
DO
RLOAD
R
FBK
V
FSOFFSET
V
FS
C
SLOPE
V
OL
Vo
H
PWM
FREQ
I
SINK
= 6mA
I
SOURCE
= -6mA
T
A
= +25°C to +125°C
T
A
= -40°C to +125°C
V
DD
- 0.4
10.5455
-6
/C
F
-10
-20
+10
+20
0.4925
V
DD
= 3.3V, T
A
= +25°C
CONDITIONS
V
DD
= 3.3V
V
DD
= 5.5V
V
DD
= 3.3V
T
A
= +25°C to +125°C
20
-80
MIN
TYP
500
750
-40
19
60
22 ± 2.4
±12
0.5
0.5075
10
0.4
100
MAX
800
1100
+10
UNITS
µA
mV
nA
kΩ
kΩ
mV
x V
DD
pF
V
V
Hz
%
www.maximintegrated.com
Maxim Integrated
│
2
MAX31740
Ultra-Simple Fan-Speed Controller
Capacitance
(T
A
= +25°C, unless otherwise noted.)
PARAMETER
Input Capacitance
Output Capacitance
SYMBOL
C
I
C
O
(Note 9)
(Note 9)
CONDITIONS
MIN
TYP
10
15
MAX
UNITS
pF
pF
Note 2:
All voltages referenced to ground.
Note 3:
Limits are production tested at T
A
= +25°C. Limits over the operating temperature range and relevant supply voltage range
are guaranteed by design and characterization. Typical values are not guaranteed.
Note 4:
SENSE = V
DD
/2.
Note 5:
V
START
specifies the voltage change relative to V
DD
/2 that is required to start PWM. Negative value indicates lower than
V
DD
/2.
Note 6:
The typical (TYP) column indicates ±3 sigma distribution of a trimmed resistance.
Note 7:
V
FSOFFSET
is specified relative to V
DD
/2. The total error equals V
FS
+ V
FSOFFSET
.
Note 8:
For stable PWM operation, the maximum external capacitance connected to R
SLOPE
from all sources must be less than
10pF.
Note 9:
Guaranteed by design; not 100% production tested.
www.maximintegrated.com
Maxim Integrated
│
3
MAX31740
Ultra-Simple Fan-Speed Controller
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
POWER-SUPPLY CURRENT
vs. POWER-SUPPLY VOLTAGE
MAX31740 toc01
PWM_OUT OUTPUT FREQUENCY (Hz)
POWER-SUPPLY CURRENT (µA)
C
F
= 330nF,
DUTY CYCLE = 50%
+125°C
45
40
35
30
25
20
600
V
DD
= 3.3V,
C
F
= 330nF,
C
L
= 10pF
550
500
-40°C
450
3.0
3.5
4.0
4.5
5.0
5.5
6.0
-40
10
20
50
80
110
POWER-SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
THEROETICAL PWM OUTPUT FREQUENCY
vs. FREQ INPUT CAPACITANCE
MEASURED PWM OUTPUT FREQUENCY (Hz)
MAX31740 toc03
MEASURED PWM OUTPUT FREQUENCY
vs. FREQ INPUT CAPACITANCE
T
A
= +25°C
MAX31740 toc04
1.E+05
PWM OUTPUT FREQUENCY (Hz)
T
A
= +25°C
1.E+05
1.E+04
1.E+04
1.E+03
1.E+03
1.E+02
1.E+02
1.E+01
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
1.E+01
1.E-10
1.E-09
1.E-08
1.E-07
1.E-06
FREQ INPUT CAPACITANCE (F)
FREQ INPUT CAPACITANCE (F)
MAX31740 toc05
MAX31740 toc06
PWM_OUT OUTPUT VOLTAGE HIGH (V)
PWM DUTY CYCLE (%)
80
60
40
20
0
3.35
3.20
3.15
3.10
3.05
3.00
PWM_OUT OUTPUT VOLTAGE LOW (V)
V
DD
= 3.3V,
T
A
= +25°C
V
DD
= 3.3V,
T
A
= +25°C
V
DD
= 3.3V,
T
A
= +25°C
0.3
0.2
0.1
0%
15%
30%
45%
-10
-8
-6
-4
-2
0
0
0
5
10
15
20
D
MIN
BIAS (%V
DD
)
OUTPUT CURRENT (mA)
OUTPUT CURRENT (mA)
www.maximintegrated.com
Maxim Integrated
│
4
MAX31740 toc07
100
PWM DUTY CYCLE
vs. D
MIN
INPUT BIAS
3.30
PWM_OUT OUTPUT VOLTAGE HIGH
vs. OUTPUT CURRENT
0.4
PWM_OUT OUTPUT VOLTAGE LOW
vs. OUTPUT CURRENT
MAX31740 toc02
650
50
PWM_OUT OUTPUT FREQUENCY
vs. TEMPERATURE
MAX31740
Ultra-Simple Fan-Speed Controller
Pin Configuration
TOP VIEW
DMIN
SLOPE
SENSE
GND
1
2
3
4
EP
8
MAX31740
7
6
5
V
DD
PWM_OUT
D0
FREQ
+
TDFN
Pin Description
PIN
1
2
3
4
5
6
7
8
—
NAME
DMIN
SLOPE
SENSE
GND
FREQ
D0
PWM_OUT
V
DD
EP
FUNCTION
Connect to an external resistor divider to set the minimum active PWM duty cycle. (Typically between
0.05V
DD
to 0.2V
DD
depending on desired minimum duty cycle.)
Connect to an external resistor to set the slope of the temperature-PWM curve.
Thermistor Voltage Input. External NTC thermistor senses temperature. Thermistor and external resistor
form a voltage divider with a negative temperature coefficient.
Ground
Connect to external capacitor C
F
to set PWM frequency.
Duty Cycle Input. Sets the duty cycle below t
MIN
to either D
MIN
or 0%. Connect to GND for 0% or to V
DD
for D
MIN
. D0 has an internal 60kΩ (typ) pulldown resistor.
PWM CMOS output signal.
3.0V to 5.5V Supply Voltage Input. Bypass with at least a 0.01µF capacitor.
Exposed Pad. Connect to ground, but do not use as the sole ground connection point or leave
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