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LTC1695
1
FEATURES
APPLICATIO S
U
DESCRIPTIO
U
TYPICAL APPLICATIO
N
U
The LTC
1695 fan speed controller provides all the func-
tions necessary for a power management microprocessor
to regulate the speed of a 5V brushless DC fan via a 2-wire
SMBus/I
2
C interface. Fan speed is controlled according to
the system's required temperature profile and permits
lower fan power consumption, longer battery run time and
lower acoustical generated noise versus systems that
only provide simple on-off control for the fan.
The LTC1695 incorporates a 180mA low dropout linear
regulator, a 2-wire SMBus/I
2
C interface and a 6-bit DAC.
Fan speed is controlled by varying the fan's terminal
voltage through the output voltage of the LTC1695's linear
regulator. The LTC1695's output voltage is programmed
by sending a 6-bit digital code to the LTC1695 DAC via the
SMBus. To eliminate fan start-up problems at lower fan
voltages, users can enable the LTC1695's boost start
feature that provides the DAC's full-scale output voltage
for 250ms before decreasing to the programmed output
voltage.
The LTC1695 includes output current limiting and thermal
shutdown as well as status monitors that can be read back
by the microprocessor during fault conditions. The
LTC1695 is available in a 5-lead SOT-23 package.
s
Notebook Computers
s
Spot Cooling
s
Portable Instruments
s
Battery-Powered Systems
s
DC Motor Control
s
White LED Power Supplies
s
Programmable Low Dropout Regulator
s
Complete SMBus/I
2
C
TM
Brushless DC Fan Speed
Control System in a 5-Pin SOT-23 package
s
0.75
PMOS Linear Regulator with 180mA
Output Current Rating
s
0V to 4.922V Output Voltage Range Controlled by a
6-Bit DAC
s
Simple 2-Wire SMBus/I
2
C Interface
s
250ms Internal Timer Ensures Fan Start-Up
s
Current Limit and Thermal Shutdown
s
Fault Status Indication via SMBus Host Readback
SMBus/I
2
C Fan Speed
Controller in SOT-23
LTC1695
1
5
2
3
4
V
CC
GND
SCL
V
OUT
SDA
+
SYSTEM
CONTROLLER
+
4.7
F
10
F
5V DC FAN
SUNON
KDE0502PFB2-8
0.6W, 1.7 CFM
(25 25 10)mm
3
5V
1695 TA01
Fan Voltage and Current vs DAC Code
DAC CODE
0
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
120
100
80
60
40
20
0
6
5
4
3
2
1
0
30
50
1695 TA02
10
20
40
60
70
V
CC
= 5V
T
A
= 25
C
I
LOAD
V
OUT
, LTC and LT are registered trademarks of Linear Technology Corporation.
I
2
C is a trademark of Philips Electronics N.V.
LTC1695
2
Terminal Voltages
Supply Voltage (V
CC
) ............................................. 7V
All Other Inputs ........................ 0.3V to (V
CC
+ 0.3V)
Operating Temperature Range ..................... 0
C to 70
C
Junction Temperature ........................................... 125
C
Storage Temperature Range .................. 65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
ORDER PART
NUMBER
S5 PART MARKING
T
JMAX
= 125
C,
JA
= 256
C/W
SEE THE APPLICATIONS
INFORMATION SECTION.
Consult factory for Industrial and Military grade parts.
LTIY
LTC1695CS5
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
(Note 1)
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V unless otherwise stated.
4 SDA
5 V
OUT
SCL 3
V
CC
1
TOP VIEW
S5 PACKAGE
5-LEAD PLASTIC SOT-23
GND 2
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CC
Supply Voltage Range
4.5
5
5.5
V
I
CC
Supply Current, Operating
V
OUT
= Full Scale, I
LOAD
= 150mA
q
150.7
155
mA
Supply Current, Shutdown
DAC Code = 0
q
80
200
A
DAC
DAC Resolution
Guaranteed Monotonic
q
6
Bits
V
LSB
1LSB Resolution
I
LOAD
= 1mA
q
73
78
83
mV
V
OS
Offset Error
I
LOAD
= 1mA
q
1
LSB
DNL
Differential Nonlinearity
I
LOAD
= 1mA (Note 2)
q
0.75
LSB
INL
Integral Nonlinearity
I
LOAD
= 1mA (Note 2)
q
0.75
LSB
V
FS
V
OUT
, DAC Full Scale
I
LOAD
= 20mA
q
4.5
4.93
V
I
LOAD
= 150mA
q
4.5
4.9
V
V
ZS
V
OUT
, DAC Zero Scale
R
LOAD
= 1k
q
0
85
mV
R
ON(P)
P-Channel On Resistance
I
LOAD
= 150mA
0.75
Timer and Thermal Shutdown
V
UVLO
Undervoltage Lockout Voltage
Rising V
CC
q
2.3
2.9
3.5
V
T
BST_ST
Boost Start Timer
I
LOAD
= 10mA, C
LOAD
= 4.7
F
q
75
250
1000
ms
T
THERMAL
Thermal Shutdown Temperature
(Note 3)
155
C
I
FAULT
Output Current Limit Threshold
V
OUT
= 0V, DAC Code = 63
q
180
390
850
mA
SMBus SCL, SDA Inputs
V
IH
Input High Threshold
q
2.1
V
V
IL
Input Low Threshold
q
0.8
V
I
IN
Input Current
SCL, SDA = 0V or 5V
q
0.1
5
A
C
IN
Input Capacitance
(Note 3)
3
pF
t
ON
Switch On Time from
V
OUT
from Zero Scale to Full Scale,
q
50
500
s
Stop Condition (f
SMBus
= 100kHz)
I
LOAD
= 1mA, C
LOAD
= 4.7
F
t
OFF
Switch Off Time from
V
OUT
from Full Scale to Zero Scale,
q
150
500
s
Stop Condition (f
SMBus
= 100kHz)
I
LOAD
= 150mA, C
LOAD
= 4.7
F
V
OL
SDA Output Low Voltage
I
PULLUP
= 3mA
q
150
400
mV
LTC1695
3
ELECTRICAL CHARACTERISTICS
The
q
denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25
C. V
CC
= 5V unless otherwise stated.
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2: INL, DNL specs are specified under a 1mA I
LOAD
condition to keep the
linear regulator from operating in dropout at higher DAC codes. DNL is
measured from code 0 to code 63, taking into account the untrimmed offset
at code 0. Please refer to the Definitions section for more details.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
SMBus TIMING (Note 4)
f
SMB
SMBus Operating Frequency
q
10
100
kHz
t
BUF
Bus Free Time Between Stop and Start
q
4.7
s
t
HD(STA)
Hold Time After (Repeated) Start Condition
q
4.0
s
t
SU(STA)
Repeated Start Condition Setup Time
q
4.7
s
t
SU(STO)
Stop Condition Setup Time
q
4.0
s
t
HD(DAT)
Data Hold Time
q
300
ns
t
SU(DAT)
Data Setup Time
q
250
ns
t
LOW
Clock Low Period
q
4.7
s
t
HIGH
Clock High Period
q
4.0
50
s
t
f
Clock/Data Fall Time
q
300
ns
t
r
Clock/Data Rise Time
q
1000
ns
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
Note 3: This typical specification is based on lab measurements and is not
production tested.
Note 4: Guaranteed by design and not tested. Please refer to the Timing
Diagram section for additional information.
DAC CODE
0
OUTPUT VOLTAGE (V)
6
5
4
3
2
1
0
10
20
30
40
1695 G01
50
60 63
V
CC
= 5V
T
A
= 25
C
I
LOAD
= 1mA
TEMPERATURE (
C)
50
SUPPLY CURRENT (
A)
250
200
150
100
50
0
0
50
75
1695
G03
25
25
100
125
CODE 0
CODE 63
V
CC
= 5V
SUPPLY VOLTAGE (V)
4.0
SUPPLY CURRENT (
A)
6.0
1695 G02
4.5
5.0
5.5
250
200
150
100
50
0
CODE 0
CODE 63
T
A
= 25
C
Output Voltage vs
DAC Code
No Load Supply Current vs
Temperature
No Load Supply Current vs Supply
Voltage
LTC1695
4
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
TEMPERATURE (
C)
50
GROUND CURRENT (
A)
900
850
800
750
700
650
600
25
75
1695 G05
25
0
50
100
125
V
CC
= 5V
I
LOAD
= 180mA
CODE 63
LOAD CURRENT (mA)
DROPOUT VOLTAGE (mV)
175
150
125
100
75
50
25
0
1695 G06
0
20
40
80
60
100 120 140
180
160
V
CC
= 5V
T
A
= 85
C
T
A
= 40
C
T
A
= 25
C
TEMPERATURE (
C)
50
OUTPUT VOLTAGE (V)
4.95
4.93
4.91
4.89
4.87
4.85
0
50
75
1695 G09
25
25
100
125
V
CC
= 5V
CODE 63
I
LOAD
= 1mA
I
LOAD
= 150mA
TEMPERATURE (
C)
50
2.510
2.505
2.500
2.495
2.490
2.485
2.480
25
75
1695 G10
25
0
50
100
125
OUTPUT VOLTAGE (V)
V
CC
= 5V
CODE 32
I
LOAD
= 150mA
I
LOAD
= 1mA
CODE
0
DNL (LSB)
0.25
0.15
0.05
0.05
0.15
0.25
10
20
30
40
1695 G11
50
60 63
V
CC
= 5V
I
LOAD
= 1mA
CODE
0
INL (LSB)
0.25
0.15
0.05
0.05
0.15
0.25
10
20
30
40
1695 G12
50
60 63
V
CC
= 5V
I
LOAD
= 1mA
Ground Current (Dropout Mode) vs
Supply Voltage
Ground Current (Dropout Mode)
vs Temperature
Dropout Voltage vs
Load Current
Output Voltage (Full Scale) vs
Load Current
Output Voltage (Midscale) vs Load
Current
Output Voltage (Full Scale) vs
Temperature
Differential Nonlinearity (DNL)
Output Voltage (Midscale) vs
Temperature
Integral Nonlinearity
(INL)
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
4.930
4.920
4.910
4.900
4.890
4.880
4.870
4.860
1695 G07
0
20
40
60
80
120
100
140
180
160
V
CC
= 5V
T
A
= 25
C
CODE 63
LOAD CURRENT (mA)
OUTPUT VOLTAGE (V)
1695 G08
2.505
2.500
2.495
2.490
2.485
2.480
0
40
80 100
20
60
120
180
160
140
V
CC
= 5V
T
A
= 25
C
CODE 32
SUPPLY VOLTAGE (V)
4.0
GROUND CURRENT (
A)
6.0
1695 G04
4.5
5.0
5.5
900
800
700
600
500
400
T
A
=25
C
I
LOAD
= 180mA
CODE 63
LTC1695
5
TYPICAL PERFOR A CE CHARACTERISTICS
U
W
TEMPERATURE (
C)
50
SUPPLY VOLTAGE (V)
3.00
2.90
2.80
2.70
2.60
25
0
25
50
1695 G13
100
75
125
POR (RISING V
CC
)
UVLO (FALLING V
CC
)
SUPPLY VOLTAGE (V)
4.0
BOOST START TIMER (ms)
250
300
6.0
1695 G14
200
150
4.5
5.0
5.5
350
T
A
= 25
C
I
LOAD
= 10mA
TEMPERATURE (
C)
25
BOOST START TIMER (ms)
600
500
400
300
200
100
0
0
25
50
75
1695 G15
100
V
CC
= 5V
I
LOAD
= 10mA
SUPPLY VOLTAGE (V)
4.5
CURRENT LIMIT (mA)
5.5
1695 G16
4.75
5.0
5.25
425
400
375
350
325
300
T
A
= 25
C
TEMPERATURE (
C)
40
CURRENT LIMIT (mA)
600
500
400
300
200
100
0
20
0
20
40
1695 G17
60
80 90
V
CC
= 5V
LOAD CURRENT (mA)
0
20
100
140 160
JUNCTION TEMPERATURE INCREASE (
C)
120
120
100
80
60
40
20
0
1695 G18
40
60
80
180
CODE 16 (1.25V)
CODE 32 (2.5V)
CODE 48 (3.75V)
CODE 63 (4.922V)
V
CC
= 5V, T
A
= 25
C,
SOT-23 THERMAL RESISTANCE
= 150
C/W (PCB SOLDERED)
SEE APPLICATIONS
INFORMATION.
POR and UVLO vs Temperature
Boost Start Timer vs Supply
Voltage
Boost Start Timer vs Temperature
Current Limit Threshold vs
Supply Voltage
Junction Temperature Increase
vs Load Current
Current Limit Threshold
vs Temperature
Load Transient Response
Code 32, 5mA to 55mA
Load Transient Response
Code 32, 50mA to 100mA
1695 G19
V
OUT
(AC)
20mV/DIV
I
LOAD
50mA/DIV
100
s/DIV
V
CC
= 5V
C
OUT
= 4.7
F TANTALUM
1695 G20
V
OUT
(AC)
10mV/DIV
I
LOAD
50mA/DIV
100
s/DIV
V
CC
= 5V
C
OUT
= 4.7
F TANTALUM
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