FEATURES
■
Two 8-Bit Current DACs
■
DACs Guaranteed Monotonic
■
Known IC State on Power-Up
■
Serial Interface Watchdog Timer with Disable
■
2-Wire Serial Interface Compatible with I2C
and SMBus
■
2 Programmable Fan Tachometer Interfaces
■
4 Programmable General Purpose I/Os
■
Small 16-Pin SSOP Package
■
Single 2.7V to 5.75V Supply Operation
■
Fault Output Signal
■
Status Register
■
Fan Blasting Function
■
Nine Addresses Using Two Programming Lines
U
APPLICATIO S
■
Servers
■
Desktop Computers
■
Power Supplies
■
Cooling Systems
, LTC and LT are registered trademarks of Linear Technology Corporation.
I2C is a trademark of Philips Electronics N.V.
TM
LTC1840
Dual Fan Controller
with 2-Wire Interface
U
DESCRIPTIO
The LTC®1840 is a fan controller with two 8-bit current
output DACs, two tachometer interfaces, and four general
purpose I/O (GPIO) pins. It operates from a single supply
with a range of 2.7V to 5.75V. A current output DAC is used
to control an external switching regulator, which controls
the fan speed. A current output DAC and tachometer allow
a controller to form a closed control loop on fan velocity.
The GPIO pins can be used as digital inputs or open drain
pull-down outputs.
The part features a simple 2-wire I2C and SMBus compatible serial interface that allows communication between
many devices. The interface includes a fault status register
that reflects the state of the part and which can be polled
to find the cause of a fault condition. Other operational
characteristics of the part, such as DAC output currents,
GPIO modes, and tachometer frequency, are also programmed through the serial interface. Two address pins
provide nine possible device addresses.
The BLAST pin is provided to force the DAC output
currents to program the maximum regulator output
voltages through a single pin and gate the operation of the
serial access timer.
TYPICAL APPLICATIO
3.3V
3.3V
3.3V
130Ω
LED2
10k
TO
MASTER
3.3V
NC
130Ω
NC
LED1
ADDRESS = 1110010
(8 OTHERS POSSIBLE)
FAULT
SDA
SCL
A0
A1
GPI01
GPI02
V
CC
IDACOUTA
LTC1840
IDACOUTB
GND
U
Low Parts Count, High Efficiency Dual Fan Control
C
FB1
100pF
C
FB2
100pF
12V
RUN/SS
LTC1771
I
TH
V
FB
12V
RUN/SS
LTC1771
I
TH
V
FB
GND
GND
V
V
IN
SENSE
PGATE
IN
SENSE
PGATE
MODE
MODE
R
R
SENSE1
0.05Ω
SENSE2
0.05Ω
GPI04
BLAST
GPI03
TACHB
TACHA
+
10µF
SYSTEM
RESET
R
10k
R
10k
0.1µF
C1
C
C1
220pF
C2
C
C2
220pF
+
Si6447DQ
L1 47µH
UPS5817
+
Si6447DQ
L2 47µH
UPS5817
C
VIN1
22µF
R
FB1A
75k
+
R
FB1B
28k
2-NMB 6820PL-04W-B29-D50 FANS
1.1A NOM AT 12V
C
VIN2
22µF
R
FB2A
75k
+
R
FB2B
28k
C
OUT1
150µF
C
OUT2
150µF
FAN
FAN
3.3V
DC
10k
TACH
OUT
3.3V
DC
10k
TACH
OUT
1840 TA01
1840f
1
LTC1840
TOP VIEW
GN PACKAGE
16-LEAD PLASTIC SSOP
1
2
3
4
5
6
7
8
16
15
14
13
12
11
10
9
SCL
SDA
A1
A0
FAULT
GPIO1
GPIO2
GND
V
CC
I
DACOUTA
I
DACOUTB
BLAST
TACHB
TACHA
GPIO4
GPIO3
WW
W
ABSOLUTE AXI U RATI GS
U
UUW
PACKAGE/ORDER I FOR ATIO
(Note 1)
VCC to GND .................................................... –0.3 to 6V
A0, A1.............................................–0.3 to (V
I
DACOUTA
, I
DACOUTB
.............................
–0.3 to (V
+ 0.3V)
CC
+ 0.75V)
CC
All other pins ................................................. –0.3 to 6V
ORDER PART
NUMBER
LTC1840CGN
LTC1840IGN
Operating Temperature
LTC1840C ............................................... 0°C to 70°C
LTC1840I.............................................–40°C to 85°C
Storage Temperature Range ..................–65°C to 125°C
GN PART
MARKING
Lead Temperature (Soldering, 10 sec).................. 300°C
1840
T
= 125°C, θJA = 110°C/W
JMAX
Consult LTC marketing for parts specified with wider operating temperature ranges.
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3V
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
DACs
n Resolution 8 Bits
DNL Differential Nonlinearity V
INL Integral Nonlinearity V
ZSE Zero-Scale Error V
Output Voltage Rejection 1.1V< V
Output Voltage Rejection VCC = 5.75V, 1.1V < V
I
DACOUTA(FS),
I
DACOUTB(FS)
Power Supply
V
CC
I
CC
V
UVLO
V
UVHYS
Oscillator Performance
f
OSC
PSRR Supply Sensitivity 2.7V < VCC < 5.75V 0.1 0.5 %/V
GPIO Performance
I
O
V
V
V
I
LEAK
IL
IH
IHYST
Full-Scale Current Sinking 97 103 µA
Positive Supply Voltage ● 2.7 5.75 V
Supply Current VCC = 3V, A0 and A1 Floating 400 600 µA
UVLO/POR Voltage ● 2.1 2.4 2.69 V
UVLO/POR Voltage Hysteresis (Note 2) 20 90 160 mV
Oscillator Frequency ● 47 50 53 kHz
Output Current Sink V
Digital Input Low Voltage Internal Pull-Down Disabled ● 0.3V
Digital Input High Voltage Internal Pull-Down Disabled ● 0.7V
Input Hysteresis (Note 2) 50 mV
Leakage Internal Pull-Down Disabled ±1 µA
= 1.1V, Guaranteed Monotonic ● ±0.9 LSB
DACOUT
= 1.1V ± 4LSB
DACOUT
= 1.1V –0.2 0.1 2 µA
DACOUT
< 3.75V ±1LSB
DACOUT
< 6.5V ±2LSB
DACOUT
V
= 1.1V ● 95 105 µA
DACOUT
V
= 5V, A0 and A1 Floating 500 750 µA
CC
= 0.7V, Internal Pull-Down Enabled ● 10 mA
GPIOX
CC
1840I
CC
1840f
2
V
V
LTC1840
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at TA = 25°C. VCC = 3V
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Digital Inputs SCL, SDA
V
IH
V
IL
V
LTH
I
LEAK
C
IN
Digital Output SDA
V
OL
Digital Output FAULT
V
OL
Digital Inputs TACHA, TACHB
V
IH
V
IL
I
LEAK
Digital Input BLAST
V
LTH
V
IHYST
I
LEAK
Address Inputs A0, A1
V
IH
V
IL
I
IN
Timing Characteristics
f
I2C
t
BUF
t
hD, STA
t
su, STA
t
su, STO
t
hD, DAT
t
su, DAT
t
LOW
t
HIGH
t
f
t
r
Note 1: Absolute Maximum Ratings are those values beyond
which the life of a device may be impaired.
Digital Input High Voltage ● 1.4 V
Digital Input Low Voltage ● 0.6 V
Logic Threshold Voltage (Note 2) 1 V
Digital Input Leakage VCC = 5V and 0V, VIN = GND to V
CC
±1 µA
Digital Input Capacitance (Note 2) 10 pF
Digital Output Low Voltage I
Digital Output Low Voltage I
Digital Input High Voltage ● 0.7V
Digital Input Low Voltage ● 0.3V
Digital Input Leakage VCC = 5V and 0V, VIN = GND to V
= 3mA ● 0.4 V
PULL-UP
= 1mA ● 0.4 V
PULL-UP
CC
CC
CC
±1 µA
Logic Threshold Voltage Measured on BLAST Falling Edge 0.95 1.0 1.05 V
Input Hysteresis (Note 2), Measured on Rising Edge 20 mV
Digital Input Leakage VCC = 5V and 0V, VIN = GND to V
Input High Voltage ● 0.9V
CC
CC
Input Low Voltage ● 0.1V
±1 µA
CC
Input Current AX Shorted to GND or VCC, VCC = 5V ±100 µA
I2C Operating Frequency (Note 2) 0 100 kHz
Bus Free Time Between (Note 2) 4.7 µs
Stop and Start Condition
Hold Time after (Repeated) (Note 2) 4 µs
Start Condition
Repeated Start Condition (Note 2) 4.7 µs
Setup Time
Stop Condition Setup Time (Note 2) 4 µs
Data Hold Time 300 ns
Data Setup Time (Note 2) 250 ns
Clock Low Period (Note 2) 4.7 µs
Clock High Period (Note 2) 4.0 µs
Clock, Data Fall Time (Note 2) 300 ns
Clock, Data Rise Time (Note 2) 1000 ns
Note 2: Guaranteed by design not subject to test.
V
V
V
V
1840f
3
LTC1840
V
DACOUT
(V)
I
DACOUT
(µA)
100.5
100.3
100.1
99.9
99.7
99.5
99.3
99.1
1840 G06
0
1
23456
TA = 25°C
UW
TYPICAL PERFOR A CE CHARACTERISTICS
Supply Current vs Temperature
Supply Current vs Supply Voltage
550
TA = 25°C
500
(µA)
CC
I
450
450
440
430
(µA)
420
CC
I
410
400
(VCC = 3V)
100.10
100.05
(µA)
100.00
DACOUT
I
99.95
I
Full Scale vs VCC,
DACOUT
V
DACOUT
TA = 25°C
= 1.1V
400
2.5
I
DACOUT
3.5
FS vs V
at VCC = 3V to 5V
120
TA = 25°C
100
80
(µA)
60
DACOUT
I
40
20
0
0
I
DACOUT
234
1
AC Supply Rejection at
Full Scale, VCC = 3V DC
20
TA = 25°C
VCC (V)
V
DACOUT
4.5
DACOUT
(V)
5.5
56
1840 G01
1840 G04
6.5
390
–50
I
DACOUT
02550
–25
TEMPERATURE (°C)
FS vs V
DACOUT
at VCC = 3V
100.10
TA = 25°C
100.05
100.00
99.95
(µA)
99.90
DACOUT
I
99.85
99.80
99.75
0.5
1.5 2.5 4.5
V
(V)
DACOUT
DAC Zero Scale Error at VCC = 3V,
V
10
DACOUT
= 1.1V
3.5
75 100
1840 G02
1840 G05
99.90
2.5
I
DACOUT
3.5
FS vs V
4.5
VCC (V)
DACOUT
at VCC = 5V
DAC DNL vs Code at VCC = 3V
0.2
TA = 25°C
5.5
6.5
1840 G03
15
(µA/V)
CC
10
/V
DACOUT
I
5
0
1
4
10
FREQUENCY (kHz)
100
1840 G07
1000
5
DAC ZSE (nA)
0
–50
–25 0
50 100 125
25 75
TEMPERATURE (°C)
1840 G08
0.1
0
DNL (LSB)
–0.1
–0.2
1
CODE
255
1840 G09
1840f
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