Rainbow Electronics MAX5943 User Manual
General Description
The MAX5943 is a fully integrated power-management
IC for FireWire®applications. This device controls two
external power n-channel MOSFETs to regulate current
from the input power supply to the load and performs
low-voltage-drop, power-supply ORing. The MAX5943
operates over a 7.5V to 37V input range and provides
inrush and output current limit in addition to a diode
ORing function suitable for FireWire applications.
The MAX5943 allows the safe insertion and removal of
FireWire peripherals into a live FireWire port by providing
inrush current control and an output current-limiting function. The ORing feature provides a very efficient way to
protect the FireWire port when connected to another
FireWire peripheral that sources a higher voltage. By turning off both external MOSFETS, the MAX5943 provides a
true bidirectional load disconnect. A low-current shutdown mode disables the MAX5943, resulting in less than
10µA supply current. A pin-selectable input allows
latched or autoretry fault management after a fault.
The MAX5943A features a current-limit function that
actively limits the current drawn by the load with a programmable timeout. The MAX5943B–MAX5943E do not
actively limit the load current but provide a circuit-breaker
function. See the Selector Guide for the default and programmable circuit-breaker timeouts.
The MAX5943 operates over the -40°C to +85°C extended
temperature range and is available in a 16-pin QSOP
package.
Applications
FireWire Desktop/Notebook Port
FireWire Peripheral Device Current Limit
FireWire Hub
Hot Swap
Features
♦ Provides Safe Hot Swap for 7.5V to 37V Power
Supplies
♦ Low-Drop Power ORing with Ultra-Fast Turn-Off
♦ Programmable Active Current Limit (MAX5943A)
♦ Programmable Circuit Breaker
(MAX5943B–MAX5943E)
♦ ±5% Current-Limit Sensing Accuracy
♦ Programmable Current-Limit/Circuit-Breaker
Timeout
♦ Fast Current-Limit Response to Output Short-
Circuit Conditions (MAX5943A)
♦ Drives External N-Channel Power MOSFETs
♦ Overcurrent Fault Status Output
♦ Latched or Autoretry Overcurrent Fault
Management
♦ 10µA Shutdown Current
♦ ON/OFF Control Allows Undervoltage Lockout
Programming
♦ Fast Load Disconnect Control Through ON Input
MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
________________________________________________________________ Maxim Integrated Products 1
Pin Configuration
Ordering Information
19-3378; Rev 0; 8/04
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.
Typical Operating Circuit and Selector Guide appear at end
of data sheet.
FireWire is a registered trademark of Apple Computers, Inc.
PART TEMP RANGE PIN-PACKAGE
MAX5943AEEE -40°C to +85°C 16 QSOP
MAX5943BEEE -40°C to +85°C 16 QSOP
MAX5943CEEE -40°C to +85°C 16 QSOP
MAX5943DEEE -40°C to +85°C 16 QSOP
MAX5943EEEE -40°C to +85°C 16 QSOP
TOP VIEW
FAULT
TIM
ILIM
LATCH
OR_ADJ
N.C.
ONQ1
ON
1
2
3
MAX5943
4
5
6
7
8
QSOP
16
IN
15
SENSE
14
GATE1
13
N.C.
12
GATE2
OUT
11
10
N.C.
9
GND
MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(VIN= 7.5V to 37V, GND = 0V, and TA= -40°C to +85°C, unless otherwise noted. Typical values are at VIN= 12V, TA= +25°C.)
(Note 1)
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.
(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 (internally clamped).........................-0.3V to +8V
FAULT.....................................................................-0.3V to +85V
ON, TIM, ILIM, LATCH, OR_ADJ, ONQ1 ..........-0.3V to (IN + 0.3V)
Continuous Power Dissipation (TA= +70°C)
16-Pin QSOP (derate 8.3mW/°C above +70°C)...........667mW
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
SUPPLIES
Supply Voltage Range V
Supply Current I
Shutdown Current I
IN Default Undervoltage Lockout V
IN Default Undervoltage Lockout
Hysteresis
ON Undervoltage Lockout
Threshold
ON Undervoltage Lockout
Threshold Hysteresis
ON Input Bias Current I
GATE2 (current-limit/circuit-breaker control)
GATE2 Pullup Current I
GATE2 High Voltage V
Current-Limit/Circuit-Breaker
Threshold Voltage
Fast Pulldown Current-Limit
Threshold Voltage (MAX5943A)
GATE2 Pulldown Current
(MAX5943A)
GATE2 Fast Pulldown Current
(MAX5943A)
GATE2 Peak Pulldown Current
(MAX5943A)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
IN
IN
SD
UVLO
V
ON_REFVON
ON
G2U
G2
V
TH
V
THF
I
G2D
I
G2DF
I
G2DP
VON = 3V, no load 1.3 2.3 mA
VON = 0.4V 5 10 µA
VIN rising, ON = IN 6.2 6.5 6.8 V
rising 1.20 1.24 1.275 V
(Note 2) 36 45 54 µA
V
GATE2
VIN - V
VIN - V
VTH < (V
t < t
ILIM
(VIN - V
4.5V
(VIN - V
- V
OUT
SENSE
(Note 3)
SENSE
- V
IN
SENSE)
> V
SENSE)
= 1V 1.0 A
SENSE)
7.5V ≤ VIN ≤ 8V 4.25 5.5 6.5
8V ≤ VIN ≤ 37V 4.5 5.5 6.5
ILIM = GND 47.5 50 52.5
ILIM = floating 37 39 41
ILIM = IN 55 58.5 61
ILIM = GND 70 75 80
ILIM = floating 54 59 64
ILIM = IN 83 88 93
< V
,
THF
THF
, V
GATE2
= V
OUT
+
7.5 37 V
0.35 V
70 mV
1µA
335 435 535 µA
80 125 200 mA
V
mV
mV
MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 7.5V to 37V, GND = 0V, and TA= -40°C to +85°C, unless otherwise noted. Typical values are at VIN= 12V, TA= +25°C.)
(Note 1)
GATE2 Pulldown Current During
Any GATE2 Turn-Off Condition
GATE1 (ORing control)
ORing Switch Turn-On Current
Threshold Voltage
ORing Switch Turn-On Current
Threshold Voltage Hysteresis
GATE1 Pullup Current I
GATE1 High Voltage V
GATE1 Turn-Off Switch OnResistance
LOGIC INPUTS
ILIM, OR_ADJ Input-Logic
Tristate Current Tolerance
(Note 6)
LATCH, ONQ1 Input-Logic Low
Voltage
LATCH, ONQ1 Input-Logic High
Voltage
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
I
G2OFF
V
GATE2
= V
+ 4.5V (Note 4) 80 125 200 mA
OUT
OR_ADJ = GND 3 5 7
V
OR
(VIN - V
SENSE
) rising
OR_ADJ = floating 5.5 7.5 9.5
mV
OR_ADJ = IN 8.5 10.5 12.8
) falling 0.5 mV
- V
IN
SENSE
- V
SENSE
) < V
7.5V ≤ V
8V ≤ V
OR
≤ 8V 4.25 5.5 6.5
IN
≤ 37V 4.5 5.5 6.5
IN
23Ω
-3 +3
ON_REF
ON_REF
ON_REF
1.8 V
V
µA
0.7 V
1µA
G1U
G1
R
G1
I
IX
I
IXL
I
IH
V
I
IL
V
(V
IN - VSENSE
(Note 5) 36 45 54 µA
V
GATE1
Measured between GATE1 and SENSE
when (V
Current into or out of input for tri-state logic
condition
Current out of input for logic low 20
Current into input for logic high 20
VON > V
IL
LATCH, ONQ1 = GND, VON > V
VON > V
IH
LATCH, ONQ1 Input Current I
TIM, ILIM, LATCH, OR_ADJ,
OUT, ONQ1 Shutdown Mode
I
Input Current
FAULT Output Low Voltage V
FAULT Output High Leakage
Current
TIMING
Current-Limit Timeout
(MAX5943A)
IH
IH_SD
OL
I
OH
t
ILIM
All voltages = VIN, VON > V
ON_REF
1µA
All voltages = VIN, VON ≤ 0.4V 1 µA
Low-impedance state, I
High-impedance state, V
= 5mA 0.12 0.25 V
FAULT
= 37V 1 µA
FAULT
TIM = IN 1.78 2.02 2.26 ms
R
= 4kΩ 0.87 1.04 1.21 ms
Current-limit mode
(Note 7)
TIM
R
= 50kΩ 9.2 11.05 12.9 ms
TIM
TIM = floating 120 175 225 ms
MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(VIN= 7.5V to 37V, GND = 0V, and TA= -40°C to +85°C, unless otherwise noted. Typical values are at VIN= 12V, TA= +25°C.)
(Note 1)
)
Note 1: All min/max parameters are tested at +25°C and +85°C. Limits at -40°C are guaranteed by design.
Note 2: Measured at both V
GATE2
= V
OUT
= 0V and V
GATE2
= V
OUT
= VIN.
Note 3: The typical value of parameter V
THF
is 1.5 x VTH.
Note 4: Current-Limit/Circuit-Breaker Timeout; IN or ON low.
Note 5: See the Typical Operating Circuit. Measured at V
GATE1
= V
SENSE
.
Note 6: The tristate (“floating”) logic condition will be entered if the pin current is within these limits.
Note 7: R
TIM
is connected from TIM to GND. The maximum timeout period is enforced to prevent arbitrarily long operation in cur-
rent-limit mode. Therefore, the relationship between resistor value and timeout changes for large values of R
TIM
. See
Current-Limit Timeout vs. R
TIM
in the Typical Operating Characteristics for nominal values.
Note 8: Parameter t
OFF
is a direct multiple of t
ILIM
(or tCB), so the limits for t
OFF
track the limits for t
ILIM
(or tCB).
Note 9: If the ON voltage goes below V
ON_REF
- Hysteresis, then GATE2 goes low immediately to disconnect power from the load
quickly (within t
ON_OFF
).
Circuit-Breaker Timeout
(MAX5943B–MAX5943E) (Note 7)
PARAMETER SYMBOL CONDITIONS MIN TYP MAX UNITS
Circuit-breaker mode,
MAX5943B
TIM = IN or
TIM ≥ 3.4V
R
= 4kΩ 27 32.5 38 µs
TIM
R
= 50kΩ 228 345 403 µs
TIM
0.45 0.51 0.57 ms
TIM = floating 3.75 5.5 7 ms
TIM = IN or
TIM ≥ 3.4V
Circuit-breaker mode,
MAX5943C
t
CB
R
= 4kΩ 54 65 76 µs
TIM
R
= 50kΩ 575 690 806 µs
TIM
TIM = floating 7.5 10.9 14 ms
0.89 1.00 1.13 ms
TIM = IN 1.78 2.02 2.26 ms
R
= 4kΩ 109 130 151 µs
Circuit-breaker mode,
MAX5943D
TIM
R
= 50kΩ 1.15 1.38 1.61 ms
TIM
TIM = floating 15 21.9 28 ms
Circuit-breaker mode,
MAX5943E
TIM = IN or
TIM ≥ 3.4V
R
= 4kΩ 217 260 303 µs
TIM
R
= 50kΩ 2.3 2.76 3.23 ms
TIM
3.56 4.05 4.52 ms
TIM = floating 30 44 56 ms
Automatic Restart Delay After
Current-Limit/Circuit-Breaker
Timeout
GATE1 Turn-Off Time
(ORing Response Time)
Turn-Off Response Time t
t
OFF
t
OR
ON_OFF
LATCH = GND (Note 8)
From VOR trigger until (V
= 10nF
C
GATE1
Time from VON < (V
until (V
GATE2
ON_OFF
- V
) < 1V, GATE2 = open
OUT
- VIN) < 1V,
GATE1
- Hysteresis)
128 x
(t
ILIM
t
CB
OR
100 ns
0.34 0.6 µs
(Note 9)
Minimum Delay from ON Low to
Low-Current Shutdown Mode
t
SD
ON step from 1.3V to 0.4V 50 µs
ms
MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
_______________________________________________________________________________________ 5
Typical Operating Characteristics
(VIN= +12V, TA= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. SUPPLY VOLTAGE
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
SUPPLY CURRENT (mA)
1.2
1.1
1.0
540
TA = +85°C
TA = +25°C
TA = -40°C
353020 251510
SUPPLY VOLTAGE (V)
CURRENT-LIMIT/CIRCUIT-BREAKER
THRESHOLD VOLTAGE vs. TEMPERATURE
62.0
ILIM = IN
61.5
61.0
60.5
60.0
59.5
59.0
58.5
58.0
THRESHOLD VOLTAGE (mV)
57.5
57.0
56.5
56.0
-40 85
VIN = 12V
VIN = 32V
VIN = 7.5V
603510-15
TEMPERATURE (°C)
6.0
5.5
5.0
MAX5943 toc01
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
SHUTDOWN SUPPLY CURRENT (µA)
0.5
0
540
THRESHOLD VOLTAGE vs. TEMPERATURE
42.0
41.5
41.0
MAX5943 toc04
40.5
40.0
39.5
39.0
38.5
38.0
THRESHOLD VOLTAGE (mV)
37.5
37.0
36.5
36.0
-40 85
CURRENT-LIMIT/CIRCUIT-BREAKER
ILIM = FLOATING
SHUTDOWN SUPPLY CURRENT
vs. SUPPLY VOLTAGE
SUPPLY VOLTAGE (V)
603510-15
TEMPERATURE (°C)
CURRENT-LIMIT/CIRCUIT-BREAKER
THRESHOLD VOLTAGE vs. TEMPERATURE
52.0
ILIM = GND
51.5
51.0
MAX5943 toc02
50.5
50.0
49.5
49.0
48.5
48.0
THRESHOLD VOLTAGE (mV)
47.5
47.0
46.5
46.0
353020 251510
MAX5943 toc05
-40 85
100
MAX5943A
10
1
TIMEOUT PERIOD (µs)
0.1
0.01
1 1000
VIN = 32V
VIN = 12V
TEMPERATURE (°C)
VIN = 7.5V
TIMEOUT PERIOD vs. R
MAX5943E
10010
R
(kΩ)
TIM
MAX5943 toc03
603510-15
TIM
MAX5943 toc06
ORing THRESHOLD VOLTAGE
vs. TEMPERATURE
12.0
11.5
11.0
10.5
10.0
9.5
9.0
8.5
8.0
7.5
7.0
6.5
6.0
5.5
ORing THRESHOLD VOLTAGE (mV)
5.0
4.5
4.0
-40 85
OR_ADJ = OPEN
OR_ADJ = GND
TEMPERATURE (°C)
OR_ADJ = IN
GATE CURRENTS vs. TEMPERATURE
47.0
46.5
MAX5943 toc07
46.0
45.5
45.0
GATE CURRENTS (µA)
44.5
6035-15 10
44.0
TEMPERATURE (°C)
GATE1
GATE2
603510-15-40 85
5.260
5.257
MAX5943 toc08
5.254
5.251
5.248
5.245
5.242
5.239
GATE1 DRIVE VOLTAGE (V)
5.236
5.233
5.230
-40 85
vs. TEMPERATURE
MAX5943 toc09
603510-15
TEMPERATURE (°C)
GATE1 DRIVE VOLTAGE
MAX5943
FireWire Current Limiter and Low-Drop
ORing Switch Controller
6 _______________________________________________________________________________________
Typical Operating Characteristics (continued)
(VIN= +12V, TA= +25°C, unless otherwise noted.)
GATE2 DRIVE VOLTAGE
vs. TEMPERATURE
MAX5943 toc10
TEMPERATURE (°C)
GATE2 DRIVE VOLTAGE (V)
603510-15
5.203
5.206
5.209
5.212
5.215
5.218
5.221
5.224
5.227
5.230
5.200
-40 85
ON HIGH VOLTAGE vs. TEMPERATURE
MAX5943 toc11
TEMPERATURE (°C)
ON HIGH VOLTAGE (V)
603510-15
1.252
1.254
1.256
1.258
1.260
1.250
-40 85
ON LOW VOLTAGE vs. TEMPERATURE
MAX5943 toc12
TEMPERATURE (°C)
ON LOW VOLTAGE (V)
603510-15-40 85
1.182
1.184
1.186
1.188
1.190
1.192
1.194
1.196
1.198
1.200
1.180
FAULT LOW VOLTAGE
vs. TEMPERATURE
MAX5943 toc13
TEMPERATURE (°C)
FAULT LOW VOLTAGE (mV)
603510-15-40 85
20
40
60
80
100
120
140
160
180
200
0
I
FAULT
= 5mA
ORing THRESHOLD RESPONSE TIME
MAX5943 toc14
I
IN
500mA/div
V
OUT
5V/div
(V
GATE
- V
SENSE
)
5V/div
V
IN
10V/div
100µs/div
OR_ADJ = IN
TURN-OFF RESPONSE TIME
MAX5943 toc15
I
IN
1A/div
V
OUT
10V/div
V
GATE2
10V/div
V
ON
2V/div
200ns/div
MAX5943A SHORT-CIRCUIT EVENT
(V
IN
= 37V)
MAX5943 toc16
I
IN
1A/div
V
OUT
50V/div
V
GATE2
50V/div
V
IN
50V/div
400µs/div
TIM = IN
ILIM = GND
V
FAULT
50V/div
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