19-3426; Rev 0; 10/04
IT
TION K
VALUA
E
BLE
AVAILA
Dual FireWire Current Limiter and Low-Drop
ORing Switch Controller
General Description
The MAX5944 is a dual, current limiter/low-drop ORing,
switch controller power-management IC for FireWire
®
applications. Each independent channel controls two
external power MOSFETs to regulate current from the
input power supply to the load and performs low-voltage-
drop power-supply ORing. The MAX5944 operates over
the 7.5V to 37V input range and provides inrush and out-
put current limit in addition to diode ORing functions suit-
able for FireWire applications.
The MAX5944 allows the safe insertion and removal of
FireWire peripherals into a live FireWire port by providing
inrush current control and output current-limiting func-
tions. The MAX5944 features a current-limit function that
actively limits the current drawn by the load with a 2ms
timeout. Its autoretry function then automatically restarts
after the 259ms autoretry delay time.
The ORing feature provides a very efficient way to pro-
tect the FireWire port when connected to another
FireWire peripheral that sources a higher voltage. By
turning off the external MOSFETS, the MAX5944 provides
a true bidirectional load disconnect. Each channel has
an independent ON/OFF control that results in less than
10µA supply current per channel.
The MAX5944 operates over the -40°C to +85°C
extended temperature range and is available in a
16-pin SO package.
Features
♦
Provides Safe Hot-Swap for 7.5V to 37V Power
Supplies
♦
Dual-Channel Hot-Swap
♦
Low-Drop Power ORing with Ultra-Fast Turn-Off
♦
Active Current Limit
♦
±5% Current-Limit Sensing Accuracy
♦
2ms Current-Limit Timeout
♦
Fast Current-Limit Response to Output
Short-Circuit Conditions
♦
Drives External n-Channel Power MOSFETs
♦
Independent Overcurrent Fault Status Outputs
♦
259ms Autoretry Period
♦
10µA (Per Channel) Shutdown Current
♦
Independent ON/OFF Control Allows
Undervoltage Lockout Programming
♦
Fast Load Disconnect Control Through
ON/OFF Inputs
♦
Bidirectional Load Disconnect
♦
Power Routing from One Port to Another
MAX5944
Applications
FireWire Desktop/Notebook Port
FireWire Peripheral Device Current Limit
FireWire Hub
Hot Swap
TOP VIEW
PART
MAX5944ESE
Ordering Information
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
16 SO
Pin Configuration
INA 1
ONA 2
FAULTA 3
ONQ1 4
OUTB 5
GATE2B 6
GATE1B 7
16 SENSEA
15 GATE1A
14 GATE2A
MAX5944
13 OUTA
12 GND
11 FAULTB
10 ONB
9
INB
Typical Operating Circuit appears at end of data sheet.
FireWire is a registered trademark of Apple Computer, Inc.
SENSEB 8
SO
1
________________________________________________________________
Maxim Integrated Products
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim’s website at www.maxim-ic.com.
Dual FireWire Current Limiter and Low-Drop
ORing Switch Controller
MAX5944
ABSOLUTE MAXIMUM RATINGS
(Voltages referenced to GND, unless otherwise noted.)
IN_ ..........................................................................-0.3V to +80V
OUT_ ......................................................................-0.3V to +80V
SENSE_ to IN_ ..........................................................-1V to +0.3V
GATE1_ to SENSE_ ..................................................-0.3V to +8V
GATE2_ to OUT_ ......................................................-0.3V to +8V
FAULT_...................................................................-0.3V
to +85V
ON_ONQ1 ...................................................................-0.3V to +85V
Continuous Power Dissipation (TA = +70°C)
16-Pin SO (derate 9.1mW/°C above +70°C)................728mW
Operating Temperature Range ...........................-40°C to +85°C
Maximum Junction Temperature .....................................+150°C
Storage Temperature Range .............................-60°C to +150°C
ESD Rating (Human Body Model)......................................2000V
Lead Temperature (soldering, 10s) .................................+300°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.
ELECTRICAL CHARACTERISTICS
(V
IN
= 7.5V to 37V, GND = 0V, and T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
IN_
= 12V, T
A
= +25°C.)
(Note 1)
PARAMETER
SUPPLIES
Supply Voltage Range
Supply Current
Shutdown Current
IN_ Default Undervoltage
Lockout
IN_ Default Undervoltage-
Lockout Hysteresis
ON_ Undervoltage-Lockout
Threshold
ON_ Undervoltage-Lockout-
Threshold Hysteresis
ON_ Input Bias Current
GATE2_
(Current-Limit Control)
GATE2_ Pullup Current (Note 2)
GATE2_ High Voltage
Current-Limit Threshold Voltage
Fast Pulldown Current-Limit
Threshold Voltage (Note 3)
GATE2_ Pulldown Current
GATE2_ Fast Pulldown Current
(Note 3)
I
G2U
V
G2
V
TH
V
THF
I
G2D
I
G2DF
V
GATE2_
- V
OUT_
V
IN_
- V
SENSE_
V
IN_
- V
SENSE_
V
TH
< (V
IN_
- V
SENSE_
) < V
THF
(V
IN_
- V
SENSE_
) > V
THF
,
V
GATE2_
= (V
OUT_
+ 4.5V)
7.5V
≤
V
IN
≤
8V
8V
≤
V
IN
≤
37V
36
4.25
4.5
47.5
70
335
80
45
5.5
5.5
50
75
435
125
54
6.50
6.5
52.5
80
535
200
µA
V
mV
mV
µA
mA
I
ON
V
ON_REF
V
ON_
rising
1.20
V
IN_
I
IN
I
SD
V
UVLO
V
ON_
= 3V, no load, per channel
V
ON_
= 0.4V, per channel
V
IN_
rising, ON_ = IN_
6.2
7.5
1.3
5
6.5
0.35
1.24
70
1
1.275
37
2.3
10
6.8
V
mA
µA
V
V
V
mV
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
2
_______________________________________________________________________________________
Dual FireWire Current Limiter and Low-Drop
ORing Switch Controller
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 7.5V to 37V, GND = 0V, and T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
IN_
= 12V, T
A
= +25°C.)
(Note 1)
PARAMETER
GATE2_ Peak Pulldown Current
GATE2_ Pulldown Current During
Any GATE2_ Turn-Off Condition
(Note 4)
GATE1_
(ORing Control)
ORing Switch Turn-On-Current
Threshold Voltage
ORing Switch Turn-On-Current
Threshold Voltage Hysteresis
GATE1_ Pullup Current (Note 5)
GATE1_ High Voltage
GATE1_ Turn-Off Switch On-
Resistance
LOGIC INPUTS
ONQ1 Input-Logic Low Voltage
ONQ1 Input-Logic High Voltage
ONQ1 Input Current
FAULT_
Output Low Voltage
FAULT_
Output High Leakage
Current
OUT_ Input Current
V
IL
V
IH
I
IH
V
OL
I
OH
I
OUT
Low-impedance state, I
FAULT_
= 5mA
High-impedance state, V
FAULT_
= 37V
V
ON_
= GND
0.12
V
ON_
> V
ON_REF
V
ON_
> V
ON_REF
1.8
1
0.25
1
1
0.7
V
V
µA
V
µA
µA
I
G1U
V
G1
R
G1PD
V
GATE_
- V
SENSE_
7.5V
≤
V
IN
≤
8V
8V
≤
V
IN
≤
37V
V
OR
(V
IN_
- V
SENSE_
) rising
(V
IN_
- V
SENSE_
) falling
36
4.25
4.5
3
5
0.5
45
5.5
5.5
2
54
6.50
6.5
3
7
mV
mV
µA
V
Ω
SYMBOL
I
G2DP
I
G2OFF
CONDITIONS
(V
IN_
- V
SENSE_
) = 1V
V
GATE2_
= (V
OUT_
+ 4.5V)
80
MIN
TYP
1.0
125
200
MAX
UNITS
A
mA
MAX5944
Measured between GATE1_ and SENSE_
when (V
IN_
- V
SENSE_
) < V
OR
_______________________________________________________________________________________
3
Dual FireWire Current Limiter and Low-Drop
ORing Switch Controller
MAX5944
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 7.5V to 37V, GND = 0V, and T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at V
IN_
= 12V, T
A
= +25°C.)
(Note 1)
PARAMETER
TIMING
Current-Limit Timeout
Automatic Restart Delay After
Current-Limit Timeout (Note 7)
GATE1_ Turn-Off Time
(ORing Response Time)
Turn-Off Response Time
(Note 7)
Minimum Delay from ON_ Low to
Low-Current Shutdown Mode
t
ILIM
t
OFF
t
OR
From V
OR
trigger until
(V
GATE1_
- V
IN_
) < 1V, C
GATE1_
= 10nF
Time from V
ON_
< (V
ON_OFF
- Hysteresis)
until (V
GATE2_
- V
OUT_
) < 1V,
for C
GATE2_
= open
ON_ step from 1.3V to 0.4V
Current-limit mode
1.78
240
2.02
259
100
2.26
278
ms
ms
ns
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
t
ON_OFF
0.34
0.6
µs
t
SD
50
µs
Note 1:
Note 2:
Note 3:
Note 4:
Note 5:
Note 6:
Note 7:
All min/max parameters are tested at +25°C and +85°C. Limits at -40°C are guaranteed by design.
Measured at both V
GATE2
= V
OUT
= 0V and V
GATE2
= V
OUT
= V
IN
.
The typical value of parameter V
THF
is 1.5 x V
TH
.
Current-Limit Timeout. IN_ or ON_ low.
See the
Typical Operating Circuit.
Measured at V
GATE_
= V
SENSE_
.
The tristate (“floating”) logic condition will be entered if the pin current is within these limits.
If the ON_ voltages go below V
ON_REF
- Hysteresis, then GATE2_ goes low immediately to disconnect power from the load
quickly (within t
ON_OFF
).
Typical Operating Characteristics
(V
IN_
= +12V, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
MAX5944 toc01
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SHUTDOWN SUPPLY CURRENT (µA)
MAX5944 toc02
CURRENT-LIMIT/CIRCUIT-BREAKER
THRESHOLD VOLTAGE vs. TEMPERATURE
52.0
51.5
51.0
50.5
50.0
49.5
49.0
48.5
48.0
47.5
47.0
46.5
46.0
-40
-15
MAX5944 toc03
2.0
1.9
1.8
SUPPLY CURRENT (mA)
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
5
10
15
20
25
30
35
T
A
= -40°C
T
A
= +85°C
T
A
= +25°C
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
5
10
15
20
25
30
35
40
SUPPLY VOLTAGE (V)
THRESHOLD VOLTAGE (mV)
6.0
5.5
5.0
V
IN
= 32V
V
IN
= 7.5V
V
IN
= 12V
40
10
35
60
85
SUPPLY VOLTAGE (V)
TEMPERATURE (°C)
4
_______________________________________________________________________________________
Dual FireWire Current Limiter and Low-Drop
ORing Switch Controller
MAX5944
Typical Operating Characteristics (continued)
(V
IN_
= +12V, T
A
= +25°C, unless otherwise noted.)
CURRENT-LIMIT TIMEOUT
vs. TEMPERATURE
MAX5944 toc04
ORing THRESHOLD VOLTAGE
vs. TEMPERATURE
MAX5944 toc05
GATE CURRENTS vs. TEMPERATURE
MAX5944 toc06
2.30
2.25
2.20
2.15
2.10
2.05
2.00
-40
-15
10
35
60
5.5
5.4
ORing THRESHOLD VOLTAGE (mV)
5.3
5.2
5.1
5.0
4.9
4.8
4.7
4.6
4.5
47.0
46.5
GATE CURRENTS (µA)
46.0
45.5
45.0
GATE2
44.5
44.0
GATE1
CURRENT-LIMIT TIMEOUT (ms)
85
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (
°
C)
TEMPERATURE (
°
C)
TEMPERATURE (°C)
GATE1 DRIVE VOLTAGE
vs. TEMPERATURE
MAX5944 toc07
GATE2 DRIVE VOLTAGE
vs. TEMPERATURE
MAX5944 toc08
ON HIGH VOLTAGE vs. TEMPERATURE
MAX5944 toc09
5.260
5.257
GATE1 DRIVE VOLTAGE (V)
5.254
5.251
5.248
5.245
5.242
5.239
5.236
5.233
5.230
-40
-15
10
35
60
5.230
5.227
GATE2 DRIVE VOLTAGE (V)
5.224
5.221
5.218
5.215
5.212
5.209
5.206
5.203
5.200
1.260
1.258
ON HIGH VOLTAGE (V)
1.256
1.254
1.252
1.250
-40
-15
10
35
60
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
85
TEMPERATURE (°C)
ON LOW VOLTAGE vs. TEMPERATURE
MAX5944 toc10
FAULT LOW VOLTAGE
vs. TEMPERATURE
180
FAULT LOW VOLTAGE (mV)
160
140
120
100
80
60
40
20
0
I
FAULT
= 5mA
MAX5944 toc11
1.200
1.198
1.196
ON LOW VOLTAGE (V)
1.194
1.192
1.190
1.188
1.186
1.184
1.182
1.180
-40
-15
10
35
60
200
85
-40
-15
10
35
60
85
TEMPERATURE (°C)
TEMPERATURE (°C)
_______________________________________________________________________________________
5
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