LINER LTC1695CS5

LTC1695
SMBus/I2C Fan Speed
Controller in SOT-23
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FEATURES
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DESCRIPTIO
Complete SMBus/I2CTM Brushless DC Fan Speed
Control System in a 5-Pin SOT-23 package
0.75Ω PMOS Linear Regulator with 180mA
Output Current Rating
0V to 4.922V Output Voltage Range Controlled by a
6-Bit DAC
Simple 2-Wire SMBus/I2C Interface
250ms Internal Timer Ensures Fan Start-Up
Current Limit and Thermal Shutdown
Fault Status Indication via SMBus Host Readback
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APPLICATIO S
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Notebook Computers
Spot Cooling
Portable Instruments
Battery-Powered Systems
DC Motor Control
White LED Power Supplies
Programmable Low Dropout Regulator
, LTC and LT are registered trademarks of Linear Technology Corporation.
I2C is a trademark of Philips Electronics N.V.
The LTC®1695 fan speed controller provides all the functions necessary for a power management microprocessor
to regulate the speed of a 5V brushless DC fan via a 2-wire
SMBus/I2C 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/I2C 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.
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TYPICAL APPLICATION
Fan Voltage and Current vs DAC Code
120
100
10µF
VOUT
5
+
LTC1695
2
3
SYSTEM
CONTROLLER
VCC
4.7µF
GND
SCL
SDA
5V DC FAN
SUNON
KDE0502PFB2-8
0.6W, 1.7 CFM
(25 • 25 • 10)mm3
4
5
80
4
ILOAD
VOUT
60
3
40
2
20
1
OUTPUT VOLTAGE (V)
1
+
LOAD CURRENT (mA)
5V
6
VCC = 5V
TA = 25°C
1695 • TA01
0
0
10
20
40
30
DAC CODE
50
60
0
70
1695 • TA02
1
LTC1695
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ABSOLUTE
AXI U RATI GS
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PACKAGE/ORDER I FOR ATIO
(Note 1)
Terminal Voltages
Supply Voltage (VCC) ............................................. 7V
All Other Inputs ........................ –0.3V to (VCC + 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
5 VOUT
ORDER PART
NUMBER
4 SDA
LTC1695CS5
TOP VIEW
VCC 1
GND 2
SCL 3
S5 PACKAGE
5-LEAD PLASTIC SOT-23
S5 PART MARKING
TJMAX = 125°C, θJA = 256°C/W
SEE THE APPLICATIONS
INFORMATION SECTION.
LTIY
Consult factory for Industrial and Military grade parts.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise stated.
SYMBOL
PARAMETER
VCC
Supply Voltage Range
CONDITIONS
MIN
TYP
MAX
UNITS
4.5
5
5.5
V
ICC
Supply Current, Operating
Supply Current, Shutdown
VOUT = Full Scale, ILOAD = 150mA
DAC Code = 0
●
●
150.7
80
155
200
mA
µA
DAC Resolution
Guaranteed Monotonic
●
6
DAC
73
VLSB
1LSB Resolution
ILOAD = 1mA
●
83
mV
VOS
Offset Error
ILOAD = 1mA
●
±1
LSB
DNL
Differential Nonlinearity
ILOAD = 1mA (Note 2)
●
±0.75
LSB
INL
Integral Nonlinearity
ILOAD = 1mA (Note 2)
●
±0.75
LSB
VFS
VOUT, DAC Full Scale
ILOAD = 20mA
ILOAD = 150mA
●
●
VZS
VOUT, DAC Zero Scale
RLOAD = 1kΩ
●
RON(P)
P-Channel On Resistance
ILOAD = 150mA
4.5
4.5
78
Bits
4.93
4.9
0
V
V
85
mV
Ω
0.75
Timer and Thermal Shutdown
VUVLO
Undervoltage Lockout Voltage
Rising VCC
●
2.3
2.9
3.5
TBST_ST
Boost Start Timer
ILOAD = 10mA, CLOAD = 4.7µF
●
75
250
1000
TTHERMAL
Thermal Shutdown Temperature
(Note 3)
IFAULT
Output Current Limit Threshold
VOUT = 0V, DAC Code = 63
°C
155
●
180
●
2.1
390
V
ms
850
mA
SMBus SCL, SDA Inputs
VIH
Input High Threshold
VIL
Input Low Threshold
IIN
Input Current
SCL, SDA = 0V or 5V
CIN
Input Capacitance
(Note 3)
tON
Switch On Time from
Stop Condition (fSMBus = 100kHz)
VOUT from Zero Scale to Full Scale,
ILOAD = 1mA, CLOAD = 4.7µF
●
50
500
µs
tOFF
Switch Off Time from
Stop Condition (fSMBus = 100kHz)
VOUT from Full Scale to Zero Scale,
ILOAD = 150mA, CLOAD = 4.7µF
●
150
500
µs
VOL
SDA Output Low Voltage
IPULLUP = 3mA
●
150
400
mV
2
V
●
●
±0.1
0.8
V
±5
µA
3
pF
LTC1695
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 5V unless otherwise stated.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
100
kHz
SMBus TIMING (Note 4)
fSMB
SMBus Operating Frequency
●
10
tBUF
Bus Free Time Between Stop and Start
●
4.7
µs
tHD(STA)
Hold Time After (Repeated) Start Condition
●
4.0
µs
tSU(STA)
Repeated Start Condition Setup Time
●
4.7
µs
tSU(STO)
Stop Condition Setup Time
●
4.0
µs
tHD(DAT)
Data Hold Time
●
300
ns
tSU(DAT)
Data Setup Time
●
250
ns
tLOW
Clock Low Period
●
4.7
µs
tHIGH
Clock High Period
●
4.0
tf
Clock/Data Fall Time
tr
Clock/Data Rise Time
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 ILOAD 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.
50
µs
●
300
ns
●
1000
ns
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.
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TYPICAL PERFOR A CE CHARACTERISTICS
Output Voltage vs
DAC Code
6
VCC = 5V
TA = 25°C
CODE 63
3
2
SUPPLY CURRENT (µA)
4
150
CODE 0
100
0
10
20
30
40
DAC CODE
50
60 63
1695 • G01
0
150
100
CODE 0
50
50
1
CODE 63
200
200
SUPPLY CURRENT (µA)
OUTPUT VOLTAGE (V)
250
250
VCC = 5V
TA = 25°C
ILOAD = 1mA
5
0
No Load Supply Current vs
Temperature
No Load Supply Current vs Supply
Voltage
4.0
5.0
4.5
5.5
SUPPLY VOLTAGE (V)
6.0
1695 • G02
0
–50
–25
50
25
0
75
TEMPERATURE (°C)
100
125
1695 • G03
3
LTC1695
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TYPICAL PERFOR A CE CHARACTERISTICS
Ground Current (Dropout Mode) vs
Supply Voltage
Ground Current (Dropout Mode)
vs Temperature
900
CODE 63
700
600
500
175
VCC = 5V
ILOAD = 180mA
850
800
GROUND CURRENT (µA)
GROUND CURRENT (µA)
TA =25°C
ILOAD = 180mA
800
CODE 63
750
700
650
5.0
4.5
5.5
SUPPLY VOLTAGE (V)
4.0
TA = 25°C
75
50
100
125
0
4.930
VCC = 5V
CODE 63
VCC = 5V
TA = 25°C
4.93
4.880
OUTPUT VOLTAGE (V)
OUTPUT VOLTAGE (V)
4.890
60 80 100 120 140 160 180
LOAD CURRENT (mA)
Output Voltage (Full Scale) vs
Temperature
2.500
CODE 63
40
4.95
2.505
VCC = 5V
TA = 25°C
4.900
20
1695 • G06
Output Voltage (Midscale) vs Load
Current
4.910
TA = – 40°C
1695 • G05
Output Voltage (Full Scale) vs
Load Current
OUTPUT VOLTAGE (V)
100
0
50
25
75
0
TEMPERATURE (°C)
1695 • G04
4.920
TA = 85°C
125
25
600
–50 –25
6.0
VCC = 5V
150
DROPOUT VOLTAGE (mV)
900
400
Dropout Voltage vs
Load Current
2.495
CODE 32
2.490
ILOAD = 1mA
4.91
ILOAD = 150mA
4.89
4.87
2.485
4.870
4.860
2.480
0
20
40
0
60 80 100 120 140 160 180
LOAD CURRENT (mA)
20
40
1695 • G07
2.505
100
125
Integral Nonlinearity (INL)
0.25
VCC = 5V
ILOAD = 1mA
0.15
0.15
0.05
0.05
VCC = 5V
ILOAD = 1mA
2.495
INL (LSB)
ILOAD = 1mA
DNL (LSB)
OUTPUT VOLTAGE (V)
50
0
75
25
TEMPERATURE (°C)
1695 • G09
Differential Nonlinearity (DNL)
0.25
VCC = 5V
CODE 32
2.500
–25
1695 • G08
Output Voltage (Midscale) vs
Temperature
2.510
4.85
–50
60 80 100 120 140 160 180
LOAD CURRENT (mA)
–0.05
–0.05
2.490
ILOAD = 150mA
2.480
–50 –25
50
25
75
0
TEMPERATURE (°C)
100
125
1695 • G10
4
–0.15
–0.15
2.485
–0.25
0
10
20
30
40
CODE
50
60 63
1695 • G11
–0.25
0
10
20
30
40
CODE
50
60 63
1695 • G12
LTC1695
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TYPICAL PERFOR A CE CHARACTERISTICS
Boost Start Timer vs Supply
Voltage
POR and UVLO vs Temperature
Boost Start Timer vs Temperature
600
350
3.00
TA = 25°C
ILOAD = 10mA
UVLO (FALLING VCC)
2.80
2.70
500
BOOST START TIMER (ms)
BOOST START TIMER (ms)
SUPPLY VOLTAGE (V)
POR (RISING VCC)
2.90
VCC = 5V
ILOAD = 10mA
300
250
200
400
300
200
100
2.60
–50
–25
0
25
50
75
TEMPERATURE (°C)
100
150
4.0
125
5.0
5.5
4.5
SUPPLY VOLTAGE (V)
Current Limit Threshold vs
Supply Voltage
TA = 25°C
CURRENT LIMIT (mA)
CURRENT LIMIT (mA)
JUNCTION TEMPERATURE INCREASE (°C)
500
325
400
300
200
100
4.5
5.0
4.75
5.25
SUPPLY VOLTAGE (V)
5.5
0
–40
VCC = 5V, TA = 25°C,
SOT-23 THERMAL RESISTANCE
= 150°C/W (PCB SOLDERED)
SEE APPLICATIONS
INFORMATION.
100
80
CODE 16 (1.25V)
60
CODE 32 (2.5V)
40
20
CODE 48 (3.75V)
CODE 63 (4.922V)
0
–20
0
20
40
TEMPERATURE (°C)
60
80 90
0
20
40
60 80 100 120 140 160 180
LOAD CURRENT (mA)
1695 • G17
1695 • G16
Load Transient Response
Code 32, 5mA to 55mA
1695 • G18
Load Transient Response
Code 32, 50mA to 100mA
VOUT (AC)
20mV/DIV
VOUT (AC)
10mV/DIV
ILOAD
50mA/DIV
ILOAD
50mA/DIV
100µs/DIV
VCC = 5V
COUT = 4.7µF TANTALUM
100
120
VCC = 5V
400
75
Junction Temperature Increase
vs Load Current
600
425
350
25
50
TEMPERATURE (°C)
1695 • G15
Current Limit Threshold
vs Temperature
375
0
1695 • G14
1695 • G13
300
0
–25
6.0
1695 • G19
100µs/DIV
VCC = 5V
COUT = 4.7µF TANTALUM
1695 • G20
5
LTC1695
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TYPICAL PERFOR A CE CHARACTERISTICS
Load Transient Response
Dropout (Code 63), 5mA to 55mA
Load Transient Response
Dropout (Code 63), 50mA to 100mA
VOUT (AC)
20mV/DIV
VOUT (AC)
20mV/DIV
ILOAD
50mA/DIV
ILOAD
50mA/DIV
100µs/DIV
VCC = 5V
COUT = 4.7µF TANTALUM
1695 • G21
Boost Start Timer
VOUT
2V/DIV
100µs/DIV
VCC = 5V
COUT = 4.7µF TANTALUM
1695 • G22
VCC = 5V
CIN = 10µF
COUT = 4.7µF
ILOAD = 1mA
100ms/DIV
1695 • G23
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PIN FUNCTIONS
VCC (Pin 1): Power Supply Input. VCC supplies current to
the internal control circuitry, serves as the reference for
the 6-bit DAC and acts as the power path for the P-channel
low dropout linear regulator. Bypass VCC directly to ground
with a low ESR capacitor ≥10µF.
GND (Pin 2): Ground. Tie GND to the ground plane.
SCL (Pin 3): SMBus Clock Input. Data is shifted into SDA
on the rising edge of the SCL clock signal during data
transfer.
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SDA (Pin 4): SMBus Bidirectional Data Input/Digital Output. SDA is an open drain output and requires a pull-up
resistor or current source to VCC. Data is shifted into SDA
and acknowledged by SDA.
VOUT (Pin 5): Linear Regulator Output. Connect directly to
the fan’s +VE terminal. VOUT is set to VZS (code 0) on
power-up. For good transient response and stability, use
a general purpose, low cost, medium ESR (0.1Ω to 1Ω)
tantalum or electrolytic capacitor. LTC recommends a
surface mount tantalum capacitor of ≥4.7µF.
LTC1695
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BLOCK DIAGRA
POWER ON
RESET
AND UVLO
SHUTDOWN
CONTROL
BOOST START
TIMER
THERMAL
SHUTDOWN
6-BIT DAC
(RESISTORS,
SWITCHES)
VCC
PULL-DOWN/UP
LOGIC
–
OP AMP
P1
0.75Ω
+
6
SCL
SDA
SMBus
INTERFACE
(BUFFERS,
LOGIC)
COMMAND
REGISTER
CURRENT
LIMIT
VOUT
DATA
REGISTER
R1
50k
GND
R2
50k
1695 • BD
7
LTC1695
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SWITCHING WAVEFORMS
Boost Start Timer Measurement
ILOAD = 10mA, CLOAD = 4.7µF
VOUT = VFS
90% VFS
90% VFS
VOUT = V(CODE 32)
tBST_ST
VOUT = VZS
1695 • SW01
Output Switch On Time Measurement
Code = 63, ILOAD = 1mA, CLOAD = 4.7µF
fSMBus =100kHz
Output Switch Off Time Measurement
Code = 0, ILOAD = 150mA, CLOAD = 4.7µF
fSMBus =100kHz
STOP
CONDITION
STOP
CONDITION
12
12
D5
13
14
15
COMMAND BYTE
D4
D3
D2
16
17
18
D0
16
17
18
D1
D0
ACK
19
19
D5
D1
13
14 15
COMMAND BYTE
D4
D3
D2
ACK
VOUT = VFS
VOUT = VFS
90% VFS
VOUT = VZS
VOUT = VZS
tON
8
1695 • SW02
10% VFS
tOFF
1695 • SW03
LTC1695
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TI I G DIAGRA
Operating Sequence
SMBus SEND BYTE PROTOCOL, WITH SMBus ADDRESS = 1110100B
S
P
SCL
SDA
1
2
3
1
1
1
4
5
6
SLAVE ADDRESS
0
1
0
7
8
9
10
11
12
0
WR
ACK
X
BST
D5
13
14 15
COMMAND BYTE
D4
D3
D2
16
17
18
D1
D0
ACK
19
S = SMBus START BIT
P = SMBus STOP BIT
BST = 1 ENABLES THE BOOST START TIMER
D5 TO D0 = 6-BIT INPUT CODE FOR THE DAC (D5 = MSB)
X = DON'T CARE
SMBus RECEIVE BYTE PROTOCOL, WITH SMBus ADDRESS = 1110100B
S
P
SCL
SDA
1
2
3
1
1
1
4
5
6
SLAVE ADDRESS
0
1
0
7
8
9
0
WR
ACK
10
11
OCF THE
12
0
13
14 15
COMMAND BYTE
0
0
0
16
17
18
0
0
ACK
S = SMBus START BIT
P = SMBus STOP BIT
OCF = 1 SIGNALS THAT THE LTC1695 IS IN CURRENT LIMIT
THE = 1 SIGNALS THAT THE LTC1695 IS IN THERMAL SHUTDOWN
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1695 • TD01
Timing for SMBus Interface
STOP START
START
STOP
tBUF
SDA
tHD(STA)
tr
tHD(STA)
tf
SCL
tLOW
tHIGH
tHD(DAT)
tSU(STA)
tSU(DAT)
tSU(STO)
1695 • TD02
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LTC1695
DEFINITIONS
Resolution: The number of DAC output states (2N) that
divide the full-scale range. The resolution does not imply
linearity.
Full-Scale Voltage (VFS): The regulator output voltage
(VOUT) if all DAC bits are set to ones (code 63).
Voltage Offset Error (VOS): The regulator output voltage
if all DAC bits are set to zeros. The LDO amplifier can have
a true negative offset, but due to the LTC1695’s single
supply operation, VOUT cannot go below ground. If the
offset is negative, VOUT will remain near 0V resulting in the
transfer curve shown in Figure 1.
Table 1. Nominal VLSB and VFS values
VCC
VLSB
VFS
4.5V
70.3mV
4.430V
5.0V
78.1mV
4.922V
5.5V
85.9mV
5.414V
INL: Integral nonlinearity is the maximum deviation from
a straight line passing through the endpoints of the DAC
transfer curve. Due to the LTC1695’s single supply operation and the fact that VOUT cannot go below ground,
linearity is measured between full scale and the first code
(code 01) that guarantees a positive output. The INL error
at a given input code is calculated as follows:
INL = (VOUT – VIDEAL))/VLSB
VIDEAL = (Code • VLSB) + VOS
OUTPUT
VOLTAGE
NEGATIVE
OFFSET
VOUT = The output voltage of the DAC
measured at the given input code
0V
DAC CODE
1695 • F01
Figure 1. Effect of Negative Offset
The offset of the part is measured at the first code (code␣ 1)
that produces an output voltage 0.5LSB greater than the
previous code.
VOS = VOUT – [(Code • VFS)/(2N – 1)]
Least Significant Bit (VLSB): The least significant bit or the
ideal voltage difference between two successive codes.
VLSB = (VFS – VOS)/(2N – 1)
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DNL: Differential nonlinearity is the difference between the
measured change and the ideal 1LSB change between any
two adjacent codes. The DNL error between any two codes
is calculated as below:
DNL = (∆VOUT – VLSB)/VLSB
∆VOUT = The measured voltage difference
between two adjacent codes
The ∆VOUT calculation includes the VOS values to account
for the effect of negative offset in Figure 1. This is relevant
for code 1’s DNL.
LTC1695
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APPLICATIONS INFORMATION
OVERVIEW
The LTC1695 is a 5V brushless DC fan speed controller.
Fan speed is controlled by linear regulating the applied
voltage to the fan. To program fan speed, a system
controller or microprocessor first sends a 6-bit digital
code to the LTC1695 via a 2-wire SMBus/I2C interface. The
LTC1695’s DAC then converts this digital code into a
voltage reference. Finally, the LTC1695’s op amp loop
regulates the gate bias of the internal P-channel pass
transistor to control the corresponding output voltage.
The LTC1695 is designed for portable, power-conscious
systems that utilize small 5V brushless DC fans. These
fans are increasingly popular in providing efficient cooling
solutions in a small footprint. Smaller fans allow a user to
employ multiple fans at strategic physical locations to
govern a system’s thermal airflow (“air duct” concept).
These brushless DC fans also make use of the 5V supply
used by the main digital/analog circuitry, removing the
need for a 12V supply required by higher power fans.
The LTC1695’s P-channel linear regulator control approach offers the lowest solution component count, the
smallest PCB board space consumed, wide fan speed
control range and low acoustical/electrical generated noise.
Thermal concerns over the use of a linear regulator topology are eliminated by the fan’s generally resistive behavior. As the LTC1695 DAC codes are changed to lower the
output voltage, the voltage across the internal P-channel
pass transistor increases. However, the fan’s load current
decreases almost linearly, thereby controlling power dissipation in the regulator. For example, a Micronel 5V, 0.7W
fan (40mm2 • 12mm) draws 80mA at 4V and 20mA at 2V.
Thus the P-channel pass transistor’s power loss decreases from 80mW to 60mW.
The LTC1695 incorporates several features to simplify the
overall solution including a boost start timer to ensure fan
start-up, output current limiting and thermal shutdown.
The boost start timer is enabled via the SMBus commands
and programs VOUT to full scale for 250ms before regulating at the user programmed output voltage. This eliminates potential fan start-up problems at lower output
voltage DAC codes.
The LTC1695’s thermal shutdown circuit trips if die temperature exceeds 155°C. The P-channel pass transistor is
shut off and bit D6 in the LTC1695’s SMBus data register
is set high. If an overload or short-circuit condition occurs,
the LTC1695’s current-limit circuitry limits output current
to 390mA typically. In addition, bit D7 in the SMBus data
register is set high. The readback capability of the LTC1695
allows the host controller to monitor the status of the D6
and D7 bits for fault conditions.
SMBus Serial Interface
The LTC1695 is an SMBus slave device that supports both
SMBus send byte and receive byte protocol (Figure 2) with
two interface signals, SCL and SDA.
The SMBus host initiates communication with the LTC1695
through a start bit followed by a 7-bit address code and a
write bit. Each SMBus slave device in the system compares the address code with its specific address. For send
byte and receive byte protocol, the write bit is LOW and
HIGH respectively. If selected, the LTC1695 acknowledges by pulling SDA low.
If send byte protocol is used, the host issues an 8-bit
command code. After receiving the entire command byte,
the LTC1695 again acknowledges by pulling SDA low. At
the falling edge of the acknowledge pulse, the LTC1695’s
DAC latches in the new command byte from its shift
register.
If receive byte protocol is used, the LTC1695 acknowledges by pulling SDA low after the write bit. The LTC1695
then transmits the data byte. After the host receives the
entire data byte, the cycle is terminated by a “NOT Acknowledge” bit and a stop bit.
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LTC1695
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APPLICATIONS INFORMATION
sistor capable of sinking 3mA at less than 0.4V during the
slave acknowledge sequence.
SMBus SEND BYTE PROTOCOL
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19
1
1
1
0
1
0
0
0
0
X BST D5 D4 D3 D2 D1 D0 0
A6 A5 A4 A3 A2 A1 A0 W
START
A
S
MSB
P
LSB A
STOP
SLAVE ADDRESS
COMMAND BYTE
Early Stop Conditions
SMBus RECEIVE BYTE PROTOCOL
S
1
2
3
4
5
6
7
8
9
1
1
1
0
1
0
0
1
0 OCF THE 0
A6 A5 A4 A3 A2 A1 A0 W
START
SLAVE ADDRESS
10 11 12 13 14 15 16 17 18 19
0
0
0
0
A
0
1
P
A
STOP
DATA BYTE
S = SMBus START BIT
P = SMBus STOP BIT
BST = 1 ENABLES THE BOOST START TIMER
D5 TO D0 = 6-BIT INPUT CODE FOR THE DAC (D5 = MSB)
OCF = 1 SIGNALS THAT THE LTC1695 IS IN CURRENT LIMIT
THE = 1 SIGNALS THAT THE LTC1695 IS IN THERMAL SHUTDOWN
BIT 18 = 1 IS A NOT ACKNOWLEDGE FOR RECEIVE BYTE PROTOCOL
NOTE: DURING POWER UP AND UVLO, DAC INPUT BITS
(D5 TO D0) AND THE BST BIT ARE RESET TO ZERO
1695 • F02
Figure 2. SMBus Interface Bit Definition
SCL and SDA
SCL is the synchronizing clock signal generated by the
host. SDA is the bidirectional data transfer line between
the host and a slave device. The host initiates a start bit by
pulling SDA from high to low while SCL is high. The stop
bit is initiated by changing SDA from low to high while SCL
is high. All address, command and acknowledge signals
must be valid and should not change while SCL is high.
The acknowledge bit signals to the host the acceptance of
a correct address byte or command byte.
The SCL and SDA input threshold voltages are typically
1.4V with 40mV of hysteresis. Connect the SCL and SDA
open-drain lines to either a resistive or current source pull
up. The LTC1695 SDA has an open-drain N-channel tran-
12
The LTC1695 is compatible with the Philips/Signetics I2C
Bus Interface. The 1.4V threshold for SCL and SDA does
not create any I2C application problems.
If a stop condition occurs before the data byte is acknowledged in the write byte protocol, the LTC1695’s DAC is not
updated. Otherwise, the internal register is updated with
the new data and VOUT changes accordingly to the new
programmed value.
Address, Command, Data Selection
The LTC1695’s address is hard-wired internally as 1110100
(MSB to LSB, A6 to A0). Consult LTC for parts with
alternate address codes. Consult the Address, Command
and Data Byte Tables for further information and as a
concise reference.
As shown in Figure 2, D5 to D0 in the command code,
control the linear regulator’s output voltage and thus fan
speed. D5 to D0 are sent from the host to the LTC1695
during send byte protocol. The LTC1695 latches D5 to D0
as DAC input data at the falling edge of the data acknowledge signal. The host must set “BST” (boost start enable
bit) to high if the LTC1695’s 250ms boost start timer
option is used. All bits are reset to zero during power-on
reset and UVLO. As shown in the Timing Diagram, bit 6
and bit 7 in the data byte register are defined as thermal
shutdown status (THE) and over current fault (OCF) status
respectively. The LTC1695 sets OCF high if ILOAD exceeds
390mA typically and “THE” high if junction temperature
exceeds 155°C typically. The remaining bits of the data
byte’s register (bit 5 to 0) are set low during host read
back.
LTC1695
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APPLICATIONS INFORMATION
Linear Regulator Loop Compensation
VCC
VCC/2
64 RESISTOR
VOLTAGE TABS
GND
720
SWITCHES
6
SMBus
COMMAND
D5 to D0
REFERENCE
OP AMP
“000000” = 0V
“111111” = 0.984 • VCC/2
1695 • F03
Figure 3. Ladder DAC
DAC
The LTC1695 uses a 128-segment resistor ladder to
implement the monotonic 6-bit voltage DAC (Figure 3).
Guaranteeing monotonicity (no missing codes) permits
the use of the LTC1695 in thermal feedback control
applications. As the typical application uses a 5V supply
for VCC, the reference for the 6-bit DAC is VCC. LTC
recommends a 10µF or greater tantalum capacitor to
bypass VCC. Users must account for the variation in the
DAC’s output absolute accuracy as VCC varies. VCC voltage
should not exceed the absolute maximum rating of 7V or
drop below the typical 2.8V undervoltage lockout threshold (UVLO) during normal operation.
The LTC1695’s DAC specifications (INL, DNL, VOS) account for the offset and gain errors of the linear regulator
with respect to ILOAD. Consult the Definitions section for
more details.
The worst-case condition occurs if the LTC1695 P-channel pass transistor enters dropout at full-scale VOUT and
ILOAD. Full-scale VOUT (VFS) is 4.922V with VCC = 5V. In this
condition, loop gain drops and gain error increases. The
LTC1695 is designed for monotonicity up to VFS with DNL
and INL less than 0.75 LSB. Refer to the Electrical Characteristics and Typical Performance Characteristics for
more information.
The LTC1695’s linear regulator approach is a simple and
practical scheme for fan speed control featuring a wide and
linear dynamic range. It also introduces less noise into the
system supply rail, compared with a PWM scheme (fixed
frequency, variable duty cycle), switching regulator topology or simple ON-OFF control.
The LTC1695 linear regulator feedback loop requires a
capacitor at its output to stabilize the loop over the output
voltage and load current range. The output capacitor value
and the capacitor’s ESR value are critical in stabilizing the
LTC1695 feedback loop.
A ≥ 1µF general purpose, low to medium ESR (0.1Ω to 5Ω)
tantalum or aluminium electrolytic capacitor is sufficient
for most applications. These capacitor types offer a lowcost advantage, particularly for fan speed control applications. As the output capacitance value increases, stability
improves. A typical 4.7µF, 1Ω ESR surface mount tantalum capacitor is recommended for the optimum transient
response and frequency stability across temperature, VOUT
and ILOAD. Refer to the load transient response waveforms
in the Typical Performance Characteristics section.
The selection of the capacitor for COUT must be evaluated
by the user for temperature variation of the capacitance
and ESR value and the voltage coefficient of the capacitor
value. For example, the ESR of aluminium electrolytic
capacitors can increase dramatically at cold temperature.
Therefore, the regulator may be stable at room temperature but oscillate at cold temperature. Ceramic capacitors
with Z5U and Y5 dielectrics provide high capacitance
values in a small package, but exhibit strong voltage and
temperature coefficients (–80% in some cases). In addition, the ESR of surface mount ceramic capacitors is too
low (<0.1Ω) to provide adequate phase-lead in the feedback loop for stability.
Fan Load and CLOAD
Referring to Figure 4, CLOAD varies greatly depending on
the type of fan used. The simplest, inexpensive fans
contain no protection circuitry and input capacitance is on
the order of 200pF. More expensive fans generally incorporate a series-diode for reverse protection and input
13
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APPLICATIONS INFORMATION
Thermal Considerations
VCC
INTERNAL
DAC
OUTPUT
–
OP AMP
+
+
CGATE
P1(0.75Ω)
+
EQUIVALENT
DC FAN CIRCUIT
VOUT
1. Output current multiplied by the input/output voltage
differential: (ILOAD)(VCC – VOUT), and
CNODE
R1
LFAN
ESR
CFAN
R2
The LTC1695’s power handling capability is limited by the
maximum rated junction temperature of 125°C. Power
dissipation (PDISS) consists of two components:
+
+
2. GND pin current multiplied by the input voltage:
(IGND)(VCC).
PDISS = (ILOAD)(VCC – VOUT) + (IGND)(VCC)
COUT
TJ = PDISS • (θJA)
GND
1695 • F04
Figure 4. Regulator Feedback Loop
capacitance ranges from 2pF to 30pF. As previously
discussed, an output bypass capacitor is required to
stabilize the feedback loop. This output capacitor is in
parallel with the fan’s input capacitance and dominates the
total capacitance. Thus, stability is generally not affected
by the fan’s input capacitance. The output capacitor also
serves to filter the fan’s output ripple during commutation
of the fan’s motor.
POR and UVLO
Under start-up conditions, the LTC1695 performs a power
on reset (POR) function. The digital logic circuitry is
disabled and the regulator is held off. The SMBus command register (to the DAC’s input) and data register
(current limit and thermal shutdown status) are reset to
zero. The POR signal deactivates if VCC rises above 2.9V
typically. The LTC1695 is then allowed to communicate
with the SMBus host and drive the fan accordingly. Upon
exiting POR, the regulator’s output voltage is set to VZS
(code 0) until programmed by the SMBus host.
The LTC1695 enters UVLO if VCC falls below 2.8V typically.
Between 2.8V and 1V, the digital logic circuitry is disabled,
the command/data registers are cleared and the regulator
is shut down. In general, 100mV of hysteresis exists
between the UVLO and POR thresholds.
The LTC1695 has active current limiting and thermal
shutdown circuitry for device protection during overload
or fault condition. For continuous overload conditions, do
not exceed the 125°C maximum junction temperature
TJ(MAX). Give careful consideration to all thermal resistance sources from junction to ambient. Consider any
additional heat sources mounted in proximity to the
LTC1695. This is particularly relevant in applications
where the LTC1695’s output is loaded with a constant
ILOAD and VOUT is dynamically varied via the SMBus. At
lower DAC output voltage codes, the increased input-tooutput differential increases power dissipation if ILOAD
does not decrease.
For the LTC1695’s 5-lead SOT-23 surface mount package,
heat sinking is accomplished by using the heat spreading
capabilities of the PC board and its copper traces (in
particular, the GND pin trace).
The following table lists measured thermal resistance
results for various size boards and copper areas. All
measurements were taken in still air on 3/32" FR-4 board
with one ounce copper.
θJA)
Table 2. Measured Thermal Resistance (θ
Copper Area
Thermal Resistance
Topside*
Backside
Board Area (Junction to Ambient)
2500mm2
2500mm2
2500mm2
125°C/W
1000mm2
2500mm2
2500mm2
125°C/W
225mm2
2500mm2
2500mm2
130°C/W
100mm2
2500mm2
2500mm2
135°C/W
50mm2
2500mm2
2500mm2
150°C/W
*Device is mounted on topside
14
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APPLICATIONS INFORMATION
For further information, refer to the Junction Temperature
Increase (above ambient temperature) vs ILOAD graph in
the Typical Performance Characteristics section. This
graph provides a fast and simple junction temperature
estimation with various VOUT (DAC code) and ILOAD
combinations for a typical application.
scale (VFS) until junction temperature decreases to
approximately 105°C. This extended timer period is an
attempt to cool down the system and the LTC1695 by
running the fan at full speed. In most cases, such elevated
ambient temperatures require the fan to run at full speed
anyway. The remaining LTC1695’s functionality remains
unchanged.
Boost Start Timer
In general, a 5V brushless DC fan starts at a voltage value
higher than the voltage at which it stalls. This behavior is
directly attributed to the force necessary to overcome the
back EMF of the fan. For example, one fan measured
started at 3.5V but operated until its terminal voltage fell
below 2.1V. Therefore, users must ensure start-up in the
fan before programming the fan voltage to a value lower
than the starting voltage. Monitoring the fan’s DC current
for a stalled condition does not work due to the fan’s
resistive nature. Fans can sink load current even though
they are not rotating. Other approaches include detecting
absence of the fan’s commutation ripple current and
tachometers. In general, these approaches are more complex, require more circuitry, add cost and have to be
customized for the specific fan used.
The LTC1695 contains a programmable boost start timer
offering three flexible solutions to the user:
1.) Enable the boost start timer bit (D6 in the DAC command code). Each time a new output voltage is programmed, the timer forces VOUT to full scale (4.922V
nominal with VCC = 5V) for 250ms before assuming the
programmed output voltage value. This ensures fan start
up even if the programmed output voltage is below the
fan’s start threshold.
2.) Users may also choose to use a software timer routine
inside the host controller to power the DC fan, at full scale,
for a programmed time period before programming VOUT
to a lower desired DAC output voltage code.
3.) Users may choose a tachometer fan that feedbacks its
speed to the SMBus host. If fan stall conditions are
detected, the SMBus host re-programs the LTC1695.
Beyond a typical 125°C LTC1695 junction temperature,
the boost start timer (if activated) maintains VOUT at full
Thermal Shutdown, Overcurrent
The LTC1695 shuts down the P-channel linear regulator if
die temperature exceeds 155°C typically. The thermal
shutdown circuitry employs about 30°C of hysteresis. As
previously mentioned, the LTC1695 sets bit 6 (THE) in the
SMBus data byte register HIGH during thermal shutdown
conditions. During a fault condition, the LTC1695’s SMBus
logic continues to operate so that the SMBus host can read
back the fault status data.
During an overload or short-circuit fault condition, the
LTC1695’s current-limit detector sets bit 7 (OCF) in the
SMBus data byte register HIGH and actively limits output
current to 390mA typically. This protects the LTC1695’s
P-channel pass transistor. Under dead short conditions
with VOUT = 0V, the LTC1695 also clamps the output
current. However, the increased power dissipation
(5V • 390mA = 1.95W) eventually forces the LTC1695 into
thermal shutdown. The LTC1695 will then thermally oscillate until the fault condition is removed.
During recovery from thermal shutdown (typically 125°C),
the LTC1695 automatically activates the boost start timer,
programming the fan voltage to full scale for 250ms
(TBST_ST), before switching to the user programmed output voltage value. This again eliminates fan start-up problems if the thermal shutdown fault occurred while the fan
was previously operating at an output voltage below the
fan’s starting voltage. In addition, as discussed, the boost
start timer will keep VOUT at VFS for an extended time
period beyond TBST_ST until the LTC1695’s junction temperature drops below 105°C.
The LTC1695’s protection features protect itself, the fan,
and more importantly alerts the SMBus host to any system
thermal management fault conditions.
15
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APPLICATIONS INFORMATION
The LTC1695, in the 5-lead SOT-23 package, caters mainly
to 5V brushless DC fans, in spot cooling and notebook
computer applications, that consume less than 1W maximum. These applications typically require fan footprints
on the order of 4000mm3 to 20000mm3. Such fan sizes
are common and commercially available. Examples of
these miniature fans are the “Ultra-thin DC fan” and
“Extra-mini DC fan” from SUNON Inc. Models in these
series range from 17mm to 40mm in size, weigh from 4
grams to 10 grams and provides airflow densities from
0.65 CFM to 6 CFM.
Users must consider parameters like physical size
(L • W • H), airflow (CFM), power dissipation (W) and
acoustically generated noise (dBA) when choosing a fan.
Users must also evaluate the fan’s I-V characteristics
versus fan speed and the start/stall characteristics of the
fan. Other factors include mechanical considerations such
as low cost sleeve bearings or ball bearings that have
better long term reliability. Finally, users must consider if
the fan requires any input protection features such as
reverse-voltage protection. All of these factors affect the
fan’s cost.
Table 3 lists some 5V fan manufacturer’s contact information.
Table 3. 5V DC Fan Manufacturers
Manufacturer
Address
SUNON Inc.
1075 W. Lambert Rd., Brea, CA 92821
Tel: (714)255-0208
Website: http://www.sunon.com
Advanced Technology
Company
1280 Liberty Way, Vista, CA 92083
Tel: (760)727-7430
Nidec America
152 Will Dr., Canton, MA 02021
Tel: (781)828-6216
Website: http://nidec.com
NMB Technologies Inc. 9730 Independence Ave., Chatsworth, CA 91311
Tel: (818)341-3355
Website: http://www.nmbtech.com
Micronel
16
1280 Liberty Way, Vista, CA 92083
Tel: (760)727-7400
Website: http://www.micronel.com
Table 4 lists some 5V brushless DC fans suitable for typical
LTC1695 fan speed control applications. Figure 5 shows
the measured I-V characteristics of these fans. For a
particular fan selection, users must determine the minimum DAC output voltage code below which the fan stalls.
Most fans continue to consume current, even in a stalled
condition.
Table 4. Some 5V DC Fans’ Characteristics
Manufacturer Part Number
Airflow Power
Size
(CFM) (W) (L • W • H)mm3
SUNON
KDE0501PFB2-8
ATC
AD0205HB-G51
0.80
0.45
25 • 25 • 10
SUNON
KDE0502PFB2-8
1.70
0.60
25 • 25 • 10
SUNON
KDE0503PFB2-8
3.20
0.60
30 • 30 • 10
0.65
0.50
20 • 20 • 10
SUNON
KDE0535PFB2-8
4.80
0.70
35 • 35 • 10
Micronel
F41MM-005XK-9
6.10
0.70
40 • 40 • 12
150
KDE0501PFB2-8
KDE0535PFB2-8
KDE0502PFB2-8
AD0205HB-G51
KDE0503PFB2-8
F41MM-005XK-9
125
CURRENT (mA)
DC FAN SELECTION
100
75
50
25
TA = 25°C
0
0
1
2
3
4
TERMINAL VOLTAGE (V)
5
1695 • F05
Figure 5. I-V Characteristics of 5V
Brushless DC Fan Samples
LTC1695
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APPLICATIONS INFORMATION
SMBus Address Byte Table
SMBus Data Byte Table (Receive Byte Protocol)
Decimal
HEX
232
E8
Send Byte to the LTC1695
SMBus Protocol
233
E9
Receive Byte from the LTC1695
The LSB of the SMBus address is the write bit. For send byte protocol,
W = 0. For Receive byte protocol, W = 1
DECIMAL
BINARY
MSB
LSB
HEX
LTC1695 Status
0
00000000
00
No Fault
128
10000000
80
Overcurrent Fault/Clamp
64
01000000
40
Thermal Shutdown
During thermal shutdown, the LTC1695’s LDO is shut off.
SMBus Command Byte Table (Send Byte Protocol)
DECIMAL
(D5 to D0)
BINARY
MSB
LSB
HEX
(D6-D7 set to 0)
Nominal VOUT(V)
ILOAD = 1mA
DECIMAL
(D5 to D0)
BINARY
MSB
LSB
HEX
(D6-D7 set to 0)
Nominal VOUT(V)
ILOAD = 1mA
0
X0000000
00
0.000
32
X0100000
20
2.500
1
X0000001
01
0.078
33
X0100001
21
2.578
2
X0000010
02
0.156
34
X0100010
22
2.656
3
X0000011
03
0.234
35
X0100011
23
2.734
4
X0000100
04
0.313
36
X0100100
24
2.813
5
X0000101
05
0.391
37
X0100101
25
2.891
6
X0000110
06
0.469
38
X0100110
26
2.969
7
X0000111
07
0.547
39
X0100111
27
3.047
8
X0001000
08
0.625
40
X0101000
28
3.125
9
X0001001
09
0.703
41
X0101001
29
3.203
10
X0001010
0A
0.781
42
X0101010
2A
3.281
11
X0001011
0B
0.859
43
X0101011
2B
3.359
12
X0001100
0C
0.938
44
X0101100
2C
3.438
13
X0001101
0D
1.016
45
X0101101
2D
3.516
14
X0001110
0E
1.094
46
X0101110
2E
3.594
15
X0001111
0F
1.172
47
X0101111
2F
3.672
16
X0010000
10
1.250
48
X0110000
30
3.750
17
X0010001
11
1.328
49
X0110001
31
3.828
18
X0010010
12
1.406
50
X0110010
32
3.906
19
X0010011
13
1.484
51
X0110011
33
3.984
20
X0010100
14
1.563
52
X0110100
34
4.063
21
X0010101
15
1.641
53
X0110101
35
4.141
22
X0010110
16
1.719
54
X0110110
36
4.219
23
X0010111
17
1.797
55
X0110111
37
4.297
24
X0011000
18
1.875
56
X0111000
38
4.375
25
X0011001
19
1.953
57
X0111001
39
4.453
26
X0011010
1A
2.031
58
X0111010
3A
4.531
27
X0011011
1B
2.109
59
X0111011
3B
4.609
28
X0011100
1C
2.188
60
X0111100
3C
4.688
29
X0011101
1D
2.266
61
X0111101
3D
4.766
30
X0011110
1E
2.344
62
X0111110
3E
4.844
31
X0011111
1F
2.422
63
X0111111
3F
4.922
D6 = 0 disables the boost start timer.
D7 = X = don’t care
D6 = 0 disables the boost start timer.
D7 = X = don’t care
17
LTC1695
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APPLICATIONS INFORMATION
SMBus Command Byte Table (Boost Start Timer Enabled)
DECIMAL
(D5 to D0)
BINARY
MSB
LSB
HEX
(D7 set to 0)
Nominal VOUT(V)
LOAD = 1mA
DECIMAL
(D5 to D0)
BINARY
MSB
LSB
HEX
(D7 set to 0)
Nominal VOUT(V)
ILOAD = 1mA
0
X1000000
40
0.000
32
X1100000
60
2.500
1
X1000001
41
0.078
33
X1100001
61
2.578
2
X1000010
42
0.156
34
X1100010
62
2.656
3
X1000011
43
0.234
35
X1100011
63
2.734
4
X1000100
44
0.313
36
X1100100
64
2.813
5
X1000101
45
0.391
37
X1100101
65
2.891
6
X1000110
46
0.469
38
X1100110
66
2.969
7
X1000111
47
0.547
39
X1100111
67
3.047
8
X1001000
48
0.625
40
X1101000
68
3.125
9
X1001001
49
0.703
41
X1101001
69
3.203
10
X1001010
4A
0.781
42
X1101010
6A
3.281
11
X1001011
4B
0.859
43
X1101011
6B
3.359
12
X1001100
4C
0.938
44
X1101100
6C
3.438
13
X1001101
4D
1.016
45
X1101101
6D
3.516
14
X1001110
4E
1.094
46
X1101110
6E
3.594
15
X1001111
4F
1.172
47
X1101111
6F
3.672
16
X1010000
50
1.250
48
X1110000
70
3.750
17
X1010001
51
1.328
49
X1110001
71
3.828
18
X1010010
52
1.406
50
X1110010
72
3.906
19
X1010011
53
1.484
51
X1110011
73
3.984
20
X1010100
54
1.563
52
X1110100
74
4.063
21
X1010101
55
1.641
53
X1110101
75
4.141
22
X1010110
56
1.719
54
X1110110
76
4.219
23
X1010111
57
1.797
55
X1110111
77
4.297
24
X1011000
58
1.875
56
X1111000
78
4.375
25
X1011001
59
1.953
57
X1111001
79
4.453
26
X1011010
5A
2.031
58
X1111010
7A
4.531
27
X1011011
5B
2.109
59
X1111011
7B
4.609
28
X1011100
5C
2.188
60
X1111100
7C
4.688
29
X1011101
5D
2.266
61
X1111101
7D
4.766
30
X1011110
5E
2.344
62
X1111110
7E
4.844
31
X1011111
5F
2.422
63
X1111111
7F
4.922
D6 = 1 enables the boost start timer.
D7 = X = don’t care
18
D6 = 1 enables the boost start timer.
D7 = X = don’t care
LTC1695
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PACKAGE DESCRIPTIO
Dimensions in inches (millimeters) unless otherwise noted.
S5 Package
5-Lead Plastic SOT-23
(LTC DWG # 05-08-1633)
2.80 – 3.00
(0.110 – 0.118)
(NOTE 3)
2.60 – 3.00
(0.102 – 0.118)
1.50 – 1.75
(0.059 – 0.069)
0.35 – 0.55
(0.014 – 0.022)
1.90
(0.074)
REF
0.00 – 0.15
(0.00 – 0.006)
0.09 – 0.20
(0.004 – 0.008)
(NOTE 2)
0.95
(0.037)
REF
0.90 – 1.45
(0.035 – 0.057)
0.35 – 0.50
0.90 – 1.30
(0.014 – 0.020)
(0.035 – 0.051)
FIVE PLACES (NOTE 2)
S5 SOT-23 0599
NOTE:
1. DIMENSIONS ARE IN MILLIMETERS
2. DIMENSIONS ARE INCLUSIVE OF PLATING
3. DIMENSIONS ARE EXCLUSIVE OF MOLD FLASH AND METAL BURR
4. MOLD FLASH SHALL NOT EXCEED 0.254mm
5. PACKAGE EIAJ REFERENCE IS SC-74A (EIAJ)
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
19
LTC1695
U
TYPICAL APPLICATION
SMBus I2C Controlled White LED Driver
5V
1
C1
10µF
6.3V
+
SCL
2
3
LTC1695
VOUT
VCC
5
C2 +
10µF
10V
GND
SCL
SDA
R1
100Ω
R2
100Ω
R3
100Ω
R4
100Ω
R5
100Ω
R6
100Ω
LED1
LED2
LED3
LED4
LED5
LED6
4
TO
µC
LED = Hewlett Packard HLMP-CW30
C2 = SPRAGUE 595D106X0010A2T
SDA
1695 • TA03a
Output Voltage vs LED Current
20
18
LED CURRENT (mA)
16
14
12
10
8
6
4
2
VFS
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT VOLTAGE (V)
1695 • TA03b
RELATED PARTS
PART NUMBER
DESCRIPTION
COMMENTS
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Quiescent Current
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SMBus Accelerator
Improved SMBus/I2C Rise Time,
Ensures Data Integrity with Multiple SMBus/I2C Devices
LT1761
100mA, Low Noise, LDO Micropower Regulator
0.3V Dropout Voltage at 100mA, SOT-23 Package
LT1762
150mA, Low Noise, LDO Micropower Regulator
0.3V Dropout Voltage at 150mA, MSOP Package
LT1786F
SMBus Controlled CCFL Switching Regulator
1.25A, 200kHz, Floating or Grounded Lamp Configurations
20
Linear Technology Corporation
1695f LT/TP 0400 4K • PRINTED IN USA
1630 McCarthy Blvd., Milpitas, CA 95035-7417
(408)432-1900 ● FAX: (408) 434-0507 ● www.linear-tech.com
 LINEAR TECHNOLOGY CORPORATION 2000