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LTC1840IGN#TRPBF

P1-P3P4-P6P7-P9P10-P12
LTC1840
1
1840f
APPLICATIO S
U
DESCRIPTIO
U
FEATURES
TYPICAL APPLICATIO
U
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 I
2
C and SMBus compat-
ible 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 pro-
grammed 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.
■
Servers
■
Desktop Computers
■
Power Supplies
■
Cooling Systems
■
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 I
2
C
TM
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
Dual Fan Controller
with 2-Wire Interface
1840 TA01
+
C
FB1
100pF
C
C1
220pF
R
SENSE1
0.05Ω
R
SENSE2
0.05Ω
R
FB1A
75k
R
FB1B
28k
C
OUT1
150µF
+
DC
FAN
C
VIN1
22µF
L1 47µH
Si6447DQ
UPS5817
TACH
OUT
3.3V
3.3V
3.3V
3.3V
3.3V
GND
V
CC
+
C
FB2
100pF
C
C2
220pF
R
FB2A
75k
R
FB2B
28k
C
OUT2
150µF
+
DC
FAN
C
VIN2
22µF
L2 47µH
Si6447DQ
UPS5817
TACH
OUT
3.3V
12V
12V
SYSTEM
RESET
GPI04
BLAST
IDACOUTA
GPI03
IDACOUTB
TACHB
TACHA
FAULT
SDA
SCL
A0
A1
GPI01
GPI02
LTC1840
R
C1
10k
R
C2
10k
TO
MASTER
NC
NC
130Ω
LED1
130Ω
LED2
ADDRESS = 1110010
(8 OTHERS POSSIBLE)
2-NMB 6820PL-04W-B29-D50 FANS
1.1A NOM AT 12V
10k
10k
10k
+
10µF
0.1µF
RUN/SS
I
TH
V
FB
GND
V
IN
SENSE
PGATE
MODE
LTC1771
RUN/SS
I
TH
V
FB
GND
V
IN
SENSE
PGATE
MODE
LTC1771
Low Parts Count, High Efficiency Dual Fan Control
, LTC and LT are registered trademarks of Linear Technology Corporation.
I
2
C is a trademark of Philips Electronics N.V.
LTC1840
2
1840f
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
V
CC
to GND .................................................... –0.3 to 6V
A0, A1.............................................–0.3 to (V
CC
+ 0.3V)
I
DACOUTA
, I
DACOUTB
.............................
–0.3 to (V
CC
+ 0.75V)
All other pins ................................................. –0.3 to 6V
Operating Temperature
LTC1840C ............................................... 0°C to 70°C
LTC1840I.............................................–40°C to 85°C
Storage Temperature Range ..................–65°C to 125°C
Lead Temperature (Soldering, 10 sec).................. 300°C
ORDER PART
NUMBER
GN PART
MARKING
T
JMAX
= 125°C, θ
JA
= 110°C/W
Consult LTC marketing for parts specified with wider operating temperature ranges.
1840
1840I
LTC1840CGN
LTC1840IGN
ABSOLUTE AXI U RATI GS
W
WW
U
PACKAGE/ORDER I FOR ATIO
UUW
(Note 1)
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3V
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
DACs
n Resolution 8 Bits
DNL Differential Nonlinearity V
DACOUT
= 1.1V, Guaranteed Monotonic ● ±0.9 LSB
INL Integral Nonlinearity V
DACOUT
= 1.1V ± 4LSB
ZSE Zero-Scale Error V
DACOUT
= 1.1V –0.2 0.1 2 µA
Output Voltage Rejection 1.1V< V
DACOUT
< 3.75V ±1LSB
Output Voltage Rejection V
CC
= 5.75V, 1.1V < V
DACOUT
< 6.5V ±2LSB
I
DACOUTA(FS),
Full-Scale Current Sinking 97 103 µA
I
DACOUTB(FS)
V
DACOUT
= 1.1V ● 95 105 µA
Power Supply
V
CC
Positive Supply Voltage ● 2.7 5.75 V
I
CC
Supply Current V
CC
= 3V, A0 and A1 Floating 400 600 µA
V
CC
= 5V, A0 and A1 Floating 500 750 µA
V
UVLO
UVLO/POR Voltage ● 2.1 2.4 2.69 V
V
UVHYS
UVLO/POR Voltage Hysteresis (Note 2) 20 90 160 mV
Oscillator Performance
f
OSC
Oscillator Frequency ● 47 50 53 kHz
PSRR Supply Sensitivity 2.7V < V
CC
< 5.75V 0.1 0.5 %/V
GPIO Performance
I
O
Output Current Sink V
GPIOX
= 0.7V, Internal Pull-Down Enabled ● 10 mA
V
IL
Digital Input Low Voltage Internal Pull-Down Disabled ● 0.3V
CC
V
V
IH
Digital Input High Voltage Internal Pull-Down Disabled ● 0.7V
CC
V
V
IHYST
Input Hysteresis (Note 2) 50 mV
I
LEAK
Leakage Internal Pull-Down Disabled ±1 µA
LTC1840
3
1840f
ELECTRICAL CHARACTERISTICS
The ● denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T
A
= 25°C. V
CC
= 3V
Note 1: Absolute Maximum Ratings are those values beyond
which the life of a device may be impaired.
Note 2: Guaranteed by design not subject to test.
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
Digital Inputs SCL, SDA
V
IH
Digital Input High Voltage ● 1.4 V
V
IL
Digital Input Low Voltage ● 0.6 V
V
LTH
Logic Threshold Voltage (Note 2) 1 V
I
LEAK
Digital Input Leakage V
CC
= 5V and 0V, V
IN
= GND to V
CC
±1 µA
C
IN
Digital Input Capacitance (Note 2) 10 pF
Digital Output SDA
V
OL
Digital Output Low Voltage I
PULL-UP
= 3mA ● 0.4 V
Digital Output FAULT
V
OL
Digital Output Low Voltage I
PULL-UP
= 1mA ● 0.4 V
Digital Inputs TACHA, TACHB
V
IH
Digital Input High Voltage ● 0.7V
CC
V
V
IL
Digital Input Low Voltage ● 0.3V
CC
V
I
LEAK
Digital Input Leakage V
CC
= 5V and 0V, V
IN
= GND to V
CC
±1 µA
Digital Input BLAST
V
LTH
Logic Threshold Voltage Measured on BLAST Falling Edge 0.95 1.0 1.05 V
V
IHYST
Input Hysteresis (Note 2), Measured on Rising Edge 20 mV
I
LEAK
Digital Input Leakage V
CC
= 5V and 0V, V
IN
= GND to V
CC
±1 µA
Address Inputs A0, A1
V
IH
Input High Voltage ● 0.9V
CC
V
V
IL
Input Low Voltage ● 0.1V
CC
V
I
IN
Input Current AX Shorted to GND or V
CC
, V
CC
= 5V ±100 µA
Timing Characteristics
f
I2C
I
2
C Operating Frequency (Note 2) 0 100 kHz
t
BUF
Bus Free Time Between (Note 2) 4.7 µs
Stop and Start Condition
t
hD, STA
Hold Time after (Repeated) (Note 2) 4 µs
Start Condition
t
su, STA
Repeated Start Condition (Note 2) 4.7 µs
Setup Time
t
su, STO
Stop Condition Setup Time (Note 2) 4 µs
t
hD, DAT
Data Hold Time 300 ns
t
su, DAT
Data Setup Time (Note 2) 250 ns
t
LOW
Clock Low Period (Note 2) 4.7 µs
t
HIGH
Clock High Period (Note 2) 4.0 µs
t
f
Clock, Data Fall Time (Note 2) 300 ns
t
r
Clock, Data Rise Time (Note 2) 1000 ns
P1-P3P4-P6P7-P9P10-P12

LTC1840IGN#TRPBF

Mfr. #:
Buy LTC1840IGN#TRPBF
Manufacturer:
Analog Devices / Linear Technology
Description:
Digital to Analog Converters - DAC Dual I2C Fan Speed Controller
Lifecycle:
New from this manufacturer.
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