February 1, 2001 1 MIC2026/2076
MIC2026/2076 Micrel
MIC2026/2076
Dual-Channel Power Distribution Switch
General Description
The MIC2026 and MIC2076 are high-side MOSFET switches
optimized for general-purpose power distribution requiring
circuit protection.
The MIC2026/76 are internally current limited and have
thermal shutdown that protects the device and load.
The MIC2076 offers “smart” thermal shutdown that reduces
current consumption in fault modes. When a thermal shut-
down fault occurs, the output is latched off until the faulty load
is removed. Removing the load or toggling the enable input
will reset the device output.
Both devices employ soft-start circuitry that minimizes inrush
current in applications where highly capacitive loads are
employed.
A fault status output flag is asserted during overcurrent and
thermal shutdown conditions. Transient faults are internally
filtered.
The MIC2026/76 are available in 8-pin DIP or 8-lead SOP.
Typical Application
ENA OUTA
FLGA IN
FLGB GND
ENB OUTB
ON/OFF
OVERCURRENT
OVERCURRENT
ON/OFF
MIC2026-2
Logic Controller
V
CC
2.7V to 5.5V
0.1µF
VIN Load
Load
V
CONT.
10k
10k
Features
•140mΩ maximum on-resistance per channel
•2.7V to 5.5V operating range
•500mA minimum continuous current per channel
•Shortcircuit protection with thermal shutdown
•Thermally isolated channels
•Fault status flag with 3ms filter eliminates false asser-
tions (MIC2026A/2076A with 10ms filter)
•Undervoltwww.sony.com/clieage lockout
•Reverse current flow blocking (no “body diode”)
•Circuit breaker mode (MIC2076)
•Logic-compatible inputs
•Soft-start circuit
•Low quiescent current
•Pin compatible with MIC2526
Applications
•USB peripherals
•General purpose power switching
•ACPI power distribution
•Notebook PCs
•PDAs
•PC card hot swap
Micrel, Inc. • 1849 Fortune Drive • San Jose, CA 95131 • USA • tel + 1 (408) 944-0800 • fax + 1 (408) 944-0970 • http://www.micrel.com
UL Recognized Component
MIC2026/2076 Micrel
MIC2026/2076 2 February 1, 2001
Ordering Information
Part Number Enable Temperature Range Package
MIC2026x-1BM Active High –40°C to +85°C 8-lead SOP
MIC2026x-2BM Active Low –40°C to +85°C 8-lead SOP
MIC2026x-1BN Active High –40°C to +85°C 8-pin DIP
MIC2026x-2BN Active Low –40°C to +85°C 8-pin DIP
MIC2076x-1BM Active High –40°C to +85°C 8-lead SOP
MIC2076x-2BM Active Low –40°C to +85°C 8-lead SOP
MIC2076x-1BN Active High –40°C to +85°C 8-pin DIP
MIC2076x-2BN Active Low –40°C to +85°C 8-pin DIP
Note. x=A; optional part that includes a 10ms Fault status delay filter. No ‘x’ denotes standard part.
Pin Description
Pin Number Pin Name Pin Function
1 ENA Switch A Enable (Input): Logic-compatible enable input. Active high (-1) or
active low (-2).
2 FLGA Fault Flag A (Output): Active-low, open-drain output. Indicates overcurrent
or thermal shutdown conditions. Overcurrent conditions must last longer
than tD in order to assert FLGA.
3 FLGB Fault Flag B (Output): Active-low, open-drain output. Low indicates
overcurrent or thermal shutdown conditions.Overcurrent conditions must last
longer than tD in order to assert FLGB.
4 ENB Switch B Enable (Input): Logic-compatible enable input. Active-high (-1) or
active-low (-2).
5 OUTB Switch B (Output)
6 GND Ground
7 IN Input: Switch and logic supply input.
8 OUTA Switch A (Output)
Pin Configuration
1
2
3
4
8
7
6
5
OUTA
IN
GND
OUTB
ENA
FLGA
FLGB
ENB
MIC2026/76
8-Lead SOP (BM)
8-Pin DIP (BN)
February 1, 2001 3 MIC2026/2076
MIC2026/2076 Micrel
Electrical Characteristics
VIN = +5V; TA = 25°C, bold values indicate –40°C ≤ TA ≤ +85°C; unless noted
Symbol Parameter Condition Min Typ Max Units
IDD Supply Current MIC20x6-1, VENA = VENB ≤ 0.8V 0.75 5 µA
(switch off), OUT = open
MIC20x6-2, VENA = VENB ≥ 2.4V 0.75 5 µA
(switch off), OUT = open
MIC20x6-1, VENA = VENB ≥ 2.4V 100 160 µA
(switch on), OUT = open
MIC20x6-2, VENA = VENB ≤ 0.8V 100 160 µA
(switch on), OUT = open
VEN Enable Input Threshold low-to-high transition 1.7 2.4 V
high-to-low transition 0.8 1.45 V
Enable Input Hysteresis 250 mV
IEN Enable Input Current VEN = 0V to 5.5V –10.01 1µA
Enable Input Capacitance 1 pF
RDS(on) Switch Resistance VIN = 5V, IOUT = 500mA 90 140 mΩ
VIN = 3.3V, IOUT = 500mA 100 170 mΩ
Output Leakage Current MIC20x6-1, VENx ≤ 0.8V; 10 µA
MIC20x6-1, VENx ≥ 2.4V, (output off)
OFF Current in MIC2076 50 µA
Latched Thermal Shutdown (during thermal shutdown state)
tON Output Turn-On Delay RL = 10Ω, CL = 1µF, see “Timing Diagrams”1.3 5ms
tROutput Turn-On Rise Time RL = 10Ω, CL = 1µF, see “Timing Diagrams”0.5 1.15 4.9 ms
RL = 10Ω, CL = 1µF, see “Timing Diagrams”1.75 ms
MIC2026A/MIC2076A
tOFF Output Turn-Off Delay RL = 10Ω, CL = 1µF, see “Timing Diagrams”35 100 µs
tFOutput Turn-Off Fall Time RL = 10Ω, CL = 1µF, see “Timing Diagrams”32 100 µs
ILIMIT Short-Circuit Output Current VOUT = 0V, enabled into short-circuit 0.5 0.9 1.25 A
Current-Limit Threshold ramped load applied to output 1.0 1.25 A
Short-Circuit Response Time VOUT = 0V to IOUT = ILIMIT 20 µs
(short applied to output)
tDOvercurrent Flag Response VIN = 5V, apply VOUT = 0V until FLG low 1.5 37ms
Delay VIN = 3.3V, apply VOUT = 0V until FLG l ow 3 ms
VIN = 5V, apply VOUT = 0V until FLG low 10 ms
MIC2026A/MIC2076A
Absolute Maxim um Ratings (Note 1)
Supply Voltage (VIN) ...................................... –0.3V to +6V
Fault Flag Voltage (VFLG)..............................................+6V
Fault Flag Current (IFLG) ............................................25mA
Output Voltage (VOUT) ..................................................+6V
Output Current (IOUT)...............................Internally Limited
Enable Input (IEN)....................................–0.3V to VIN + 3V
Storage Temperature (TS) ......................–65°C to +150 °C
ESD Rating, Note 3
Operating Ratings (Note 2)
Supply Voltage (VIN) ................................... +2.7V to +5.5V
Ambient Temperature (TA).........................–40°C to +85°C
Junction Temperature Range (TJ) ...........Internally Limited
Thermal Resistance
SOP (θJA) ..........................................................160°C/W
DIP(θJA).............................................................105°C/W
MIC2026/2076 Micrel
MIC2026/2076 4 February 1, 2001
Symbol Parameter Condition Min Typ Max Units
Undervoltage Lockout VIN rising 2.2 2.4 2.7 V
Threshold VIN falling 2.0 2.15 2.5 V
Error Flag Output IL = 10mA, VIN = 5V 10 25 Ω
Resistance IL = 10mA, VIN = 3.3V 15 40 Ω
Error Flag Off Current VFLAG = 5V 10 µA
Overtemperature Threshold TJ increasing, each switch 140 °C
Note 4 TJ decreasing, each switch 120 °C
TJ increasing, both switches 160 °C
TJ decreasing, both switches 150 °C
Note 1. Exceeding the absolute maximum rating may damage the device.
Note 2. The device is not guaranteed to function outside its operating rating.
Note 3. Devices are ESD sensitive. Handling precautions recommended.
Note 4. If there is a fault on one channel, that channel will shut down when the die reaches approximately 140°C. If the die reaches approximately
160°C, both channels will shut down, even if neither channel is in current limit.
Test Circuit
Device
Under
Test C
L
OUT
R
L
V
OUT
Timing Diagrams
90%
V
OUT
10%
90%
10%
t
R
t
F
Output Rise and Fall Times
VEN 50%
90%
VOUT 10%
tOFF
tON
Active-Low Switch Delay Times (MIC20x6-2)
VEN 50%
90%
VOUT 10%
tOFF
tON
Active-High Switch Delay Times (MIC20x6-1)
February 1, 2001 5 MIC2026/2076
MIC2026/2076 Micrel
0
20
40
60
80
100
120
140
160
180
-40 -20 0 20 40 60 80 100
CURRENT (µA)
TEMPERATURE (°C)
Supply On-Current
vs. Temperature
5V
3.3V
0
20
40
60
80
100
120
140
160
-40 -20 0 20 40 60 80 100
ON-RESISTANCE (mΩ)
TEMPERATURE (°C)
On-Resistance
vs. Temperature
5V
3.3V
I
OUT
= 500mA
0
1
2
3
4
5
-40 -20 0 20 40 60 80 100
RISE TIME (ms)
TEMPERATURE (°C)
Turn-On Rise Time
vs. Temperature
R
L
=10Ω
C
L
=1µF
V
IN
= 5V
V
IN
= 3.3V
0
50
100
150
200
2.5 3.0 3.5 4.0 4.5 5.0 5.5
CURRENT (µA)
INPUT VOLTAGE (V)
Supply On-Current
vs. Input Voltage
+85°C+25°C
-40°C
0
50
100
150
200
2.5 3.0 3.5 4.0 4.5 5.0 5.5
RESISTANCE (mΩ)
INPUT VOLTAGE (V)
On-Resistance
vs. Input Voltage
I
OUT
= 500mA
+85°C
+25°C
-40°C
0
0.5
1.0
1.5
2.0
2.5
2.5 3.0 3.5 4.0 4.5 5.0 5.5
RISE TIME (ms)
INPUT VOLTAGE (V)
Turn-On Rise Time
vs. Input Voltage
R
L
=10Ω
C
L
=1µF
+85°C
+25°C
0
200
400
600
800
1000
-40 -20 0 20 40 60 80 100
CURRENT LIMIT (mA)
TEMPERATURE (°C)
Short-Circuit Current-Limit
vs. Temperature
V
IN
= 3.3V
V
IN
= 5V
0
200
400
600
800
1000
1200
-40 -20 0 20 40 60 80 100
CURRENT LIMIT THRESHOLD (mA)
TEMPERATURE (°C)
Current-Limit Threshold
vs. Temperature
VIN = 3.3V
VIN = 5V
0
100
200
300
400
-40 -20 0 20 40 60 80 100
FALL TIME (µs)
TEMPERATURE (°C)
Fall Time
vs. Temperature
RL=10Ω
CL=1µF
VIN = 3.3V
0
100
200
300
400
500
600
700
800
2.5 3.0 3.5 4.0 4.5 5.0 5.5
CURRENT LIMIT (mA)
INPUT VOLTAGE (V)
Short-Circuit Current-Limit
vs. Input Voltage
+85°C+25°C-40°C
0
200
400
600
800
1000
1200
2.5 3.0 3.5 4.0 4.5 5.0 5.5
CURRENT LIMIT THRESHOLD (mA)
INPUT VOLTAGE (V)
Current-Limit Threshold
vs. Input Voltage
+85°C+25°C-40°C
0
50
100
150
200
250
300
2.5 3.0 3.5 4.0 4.5 5.0 5.5
RISE TIME (µs)
INPUT VOLTAGE (V)
Fall Time
vs. Input Voltage
TA = 25°C
CL = 1µF
RL = 10Ω
MIC2026/2076 Micrel
MIC2026/2076 6 February 1, 2001
0
0.5
1.0
1.5
2.0
2.5
-40 -20 0 20 40 60 80 100
ENABLE THRESHOLD (V)
TEMPERATURE (°C)
Enable Threshold
vs. Temperature
VIN = 5V
VEN RISING
VEN FALLING
0
1
2
3
4
5
-40 -20 0 20 40 60 80 100
DELAY TIME (ms)
TEMPERATURE (°C)
Flag Delay
vs. Temperature
V
IN
= 3.3V
V
IN
= 5V
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
-40 -20 0 20 40 60 80 100
SUPPLY CURRENT (µA)
TEMPERATURE (°C)
Supply Off Current
vs. Temperature
5V
3.3V
0
0.5
1.0
1.5
2.0
2.5
2.5 3.0 3.5 4.0 4.5 5.0 5.5
ENABLE THRESHOLD (V)
INPUT VOLTAGE (V)
Enable Threshold
vs. Input Voltage
TA = 25°C
VEN FALLING
VEN RISING
0
1
2
3
4
5
2.5 3.0 3.5 4.0 4.5 5.0 5.5
DELAY TIME (ms)
INPUT VOLTAGE (V)
Flag Delay
vs. Input Voltage
+85°C
+25°C
-40°C
0
0.02
0.04
0.06
0.08
0.10
0.12
0.14
0.16
0.18
2.5 3.0 3.5 4.0 4.5 5.0 5.5
SUPPLY CURRENT (µA)
VOLTAGE (V)
Supply Off Current
vs. Input Voltage
+85°C
+25°C
-40°C
0
0.5
1.0
1.5
2.0
2.5
3.0
-40 -20 0 20 40 60 80 100
UVLO THRESHOLD (V)
TEMPERATURE (°C)
UVLO Threshold
vs. Temperature
VIN RISING
VIN F ALLING
February 1, 2001 7 MIC2026/2076
MIC2026/2076 Micrel
Functional Characteristics
UVLO—VIN Rising
(MIC2026-1)
TIME (10ms/div.)
I
OUT
(100mA/div.) V
IN
(2V/div.)
V
OUT
(2V/div.) V
FLG
(2V/div.)
V
EN
= V
IN
C
L
= 57µF
RL = 35Ω
2.4V
UVLO—VIN Falling
(MIC2026-1)
TIME (100ms/div.)
I
OUT
(100mA/div.) V
IN
(2V/div.)
V
OUT
(5V/div.) V
FLG
(2V/div.)
V
EN
= V
IN
C
L
= 57µF
RL = 35Ω
2.2V
Turn-On/Turn-Off
(MIC2026-1)
TIME (10ms/div.)
I
OUT
(200mA/div.) V
EN
(10V/div.)
V
OUT
(5V/div.) V
FLG
(5V/div.)
V
IN
= 5V
C
L
= 147µF
RL = 35Ω
712mA
(Inrush Current)
140mA
Turn-On
(MIC2026-1)
TIME (500µs/div.)
I
OUT
(200mA/div.) V
EN
(10V/div.)
V
OUT
(5V/div.) V
FLG
(5V/div.)
V
IN
= 5V
C
L
= 147µF
RL = 35Ω
140mA
Turn-Off
(MIC2026-1)
TIME (5ms/div.)
I
OUT
(200mA/div.) V
EN
(10V/div.)
V
OUT
(5V/div.) V
FLG
(5V/div.)
V
IN
= 5V
C
L
= 147µF
RL = 35Ω
140mA
Enabled Into Short
(MIC2026-1)
TIME (500µs/div.)
I
OUT
(500mA/div.) V
EN
(10V/div.)
V
OUT
(5V/div.) V
FLG
(5V/div.)
V
IN
= 5V
3.1ms (t
D
)
700mA
MIC2026/2076 Micrel
MIC2026/2076 8 February 1, 2001
Inrush Current Response
(MIC2026-1)
TIME (1ms/div.)
I
OUT
(200mA/div.) V
EN
(10V/div.)
V
FLG
(5V/div.)
V
IN
= 5V
RL = 31Ω
CL = 10µF
CL = 110µFCL = 210µF
CL = 310µF
Current-Limit Response
(Ramped Load–MIC2026-1)
TIME (100ms/div.)
I
OUT
(500mA/div.) V
IN
(10V/div.)
V
OUT
(5V/div.) V
FLG
(10V/div.)
V
IN
= 5V
C
L
= 47µF
Current-Limit
Threshold
(1A) Thermal Shutdown
Thermal
Shutdown
Hysteresis
Short
Removed
Short-Circuit
Current (800mA)
Current-Limit Response
(Stepped Short—MIC2026-1)
TIME (1ms/div.)
I
OUT
(2A/div.) V
EN
(10V/div.)
V
OUT
(5V/div.) V
FLG
(5V/div.)
V
IN
= 5V
C
L
= 47µF
R
L
= stepped short
800mA
Current-Limit Response
(MIC2026-1)
TIME (50µs/div.)
I
OUT
(5A/div.) V
OUT
(5V/div.)
V
IN
= 5V
C
L
= 0
RL = stepped short
Short-Circuit (800mA)
Independent Thermal Shutdown
(MIC2026-1)
TIME (100ms/div.)
I
OUTB
(500mA/div.) V
ENB
(10V/div.)
V
FLGB
(5V/div.) V
FLGA
(5V/div.)
V
OUTA
= No Load
(No Thermal Shutdown)
Thermal Shutdown
Independent Thermal Shutdown
(MIC2026-1)
TIME (100ms/div.)
I
OUTA
(500mA/div.) V
ENA
(10V/div.)
V
FLGB
(5V/div.) V
FLGA
(5V/div.)
V
OUTB
= No Load
(No Thermal Shutdown)
Thermal Shutdown
February 1, 2001 9 MIC2026/2076
MIC2026/2076 Micrel
Thermal Shutdown
(MIC2076-2—Output Latched Off)
No Load
TIME (2.5s/div.)
I
OUTB
(500mV/div.) V
OUT
(5V/div.) V
FLG
(10V/div.)
V
IN
= 5V
C
L
= 47µF
VENB = 0V
Thermal
Shutdown
Load Removed
Output
Reset
RL = 0
Thermal Shutdown
(Output Reset by Toggling Enable—MIC2076-2)
TIME (100ms/div.)
IOUT
(500mA/div.) VEN
(10V/div.)
VOUT
(5V/div.) VFLG
(5V/div.)
VIN = 5V
Enable
Reset
Thermal
Shutdown
Output
Reset
Ramp Load
to Short
CL = 57µF
RL = 35Ω
Thermal Shutdown
(Output Reset by Removing Load—MIC2076-2)
TIME (100ms/div.)
I
OUT
(500mA/div.) V
EN
(10V/div.)
V
OUT
(5V/div.) V
FLG
(5V/div.)
V
IN
= 5V
C
L
= 47µF
Load Removed
(Output Reset)
Output
Latched Off
Thermal
Shutdown
Ramp Load
to Short
Independent Thermal Shutdown
(MIC2076-2)
TIME (2.5s/div.)
I
OUTA
(500mA/div.) V
FLGA
(5V/div.) V
FLGB
(5V/div.)
V
IN
= 5V
C
L
= 47µF
V
ENB
= 0V
V
ENA
= 0V
Output Reset
Load
Removed
No Thermal Shutdown on Channel B
Thermal
Shutdown
RL = 0 No
Load
Independent Thermal Shutdown
(MIC2076-2)
TIME (2.5s/div.)
I
OUTB
(500mA/div.) V
FLGA
(5V/div.) V
FLGB
(10V/div.)
V
IN
= 5V
C
L
= 47µF
V
ENB
= 0V
V
ENA
= 0V
Output Reset
Load
Removed
No Thermal Shutdown on Channel A
Thermal
Shutdown
RL = 0 No
Load
MIC2026/2076 Micrel
MIC2026/2076 10 February 1, 2001
Bloc k Diagram
1.2V
REFERENCE
THERMAL
SHUTDOWN
CHARGE
PUMP
OUTB
UVLO
GATE
CONTROL
IN
ENA
GATE
CONTROL
OUTA
FLGB
CHARGE
PUMP
ENB
OSC.
FLGA
CURRENT
LIMIT
CURRENT
LIMIT
GND
MIC2026/2076
FLAG
RESPONSE
DELAY
FLAG
RESPONSE
DELAY
Functional Description
Input and Output
IN is the power supply connection to the logic circuitry and the
drain of the output MOSFET. OUT is the source of the output
MOSFET. In a typical circuit, current flows from IN to OUT
toward the load. If VOUT is greater than VIN, current will flow
from OUT to IN, since the switch is bidirectional when
enabled. The output MOSFET and driver circuitry are also
designed to allow the MOSFET source to be externally forced
to a higher voltage than the drain (VOUT > VIN) when the
switch is disabled. In this situation, the MIC2026/76 prevents
undesirable current flow from OUT to IN.
Thermal Shutdown
Thermal shutdown is employed to protect the device from
damage should the die temperature exceed safe margins
due mainly to short circuit faults. Each channel employs its
own thermal sensor. Thermal shutdown shuts off the output
MOSFET and asserts the FLG output if the die temperature
reaches 140°C and the overheated channel is in current limit.
The other channel is not effected. If however, the die tem-
perature exceeds 160°C, both channels will be shut off. Upon
determining a thermal shutdown condition, the MIC2076 will
latch the output off. In this case, a pull-up current source is
activated. This allows the output latch to automatically reset
when the load (such as a USB device) is removed. The output
can also be reset by toggling EN. Refer to Figure 1 for timing
details.
The MIC2026 will automatically reset its output when the die
temperature cools down to 120°C. The MIC2026 output and
FLG signal will continue to cycle on and off until the device is
disabled or the fault is removed. Figure 2 depicts typical
timing.
Depending on PCB layout, package, ambient temperature,
etc., it may take several hundred milliseconds from the
incidence of the fault to the output MOSFET being shut off.
This time will be shortest in the case of a dead short on the
output.
Power Dissipation
The device’s junction temperature depends on several fac-
tors such as the load, PCB layout, ambient temperature and
package type. Equations that can be used to calculate power
dissipation of each channel and junction temperature are
found below.
PD = RDS(on) × IOUT2
Total power dissipation of the device will be the summation of
PD for both channels. To relate this to junction temperature,
the following equation can be used:
TJ = PD × θJA + TA
where:
TJ = junction temperature
TA = ambient temperature
θJA = is the thermal resistance of the package
February 1, 2001 11 MIC2026/2076
MIC2026/2076 Micrel
Current Sensing and Limiting
The current-limit threshold is preset internally. The preset
level prevents damage to the device and external load but still
allows a minimum current of 500mA to be delivered to the
load.
The current-limit circuit senses a portion of the output MOSFET
switch current. The current-sense resistor shown in the block
diagram is virtual and has no voltage drop. The reaction to an
overcurrent condition varies with three scenarios:
Switch Enabled into Short-Circuit
If a switch is enabled into a heavy load or short-circuit, the
switch immediately enters into a constant-current mode,
reducing the output voltage. The FLG signal is asserted
indicating an overcurrent condition.
Short-Circuit Applied to Enabled Output
When a heavy load or short-circuit is applied to an enabled
switch, a large transient current may flow until the current-
limit circuitry responds. Once this occurs the device limits
current to less than the short-circuit current limit specification.
Current-Limit Response—Ramped Load
The MIC2026/76 current-limit profile exhibits a small foldback
effect of about 200mA. Once this current-limit threshold is
exceeded the device switches into a constant current mode.
It is important to note that the device will supply current up to
the current-limit threshold.
V
EN
V
OUT
I
OUT
Short-Circuit Fault
Thermal
Shutdown
Reached
Load and Fault Removed
(Output Reset)
V
FLG
I
LIMIT
I
LOAD
3ms typ.
delay
Figure 1. MIC2076-2 Fault Timing: Output Reset by Removing Load
VEN
VOUT
IOUT
Short-Circuit Fault
Thermal
Shutdown
Reached
Load/Fault
Removed
VFLG
ILOAD
ILIMIT
3ms typ.
delay
Figure 2. MIC2026-2 Fault Timing
Fault Flag
The FLG signal is an N-channel open-drain MOSFET output.
FLG is asserted (active-low) when either an overcurrent or
thermal shutdown condition occurs. In the case of an overcur-
rent condition, FLG will be asserted only after the flag
response delay time, tD, has elapsed. This ensures that FLG
is asserted only upon valid overcurrent conditions and that
erroneous error reporting is eliminated. For example, false
overcurrent conditions can occur during hot plug events
when a highly capacitive load is connected and causes a high
transient inrush current that exceeds the current-limit thresh-
old for up to 1ms. The FLG response delay time tD is typically
3ms (10ms the MIC2026A and MIC2027A).
Undervoltage LockMIC2026A/MIC2076Aout
Undervoltage lockout (UVLO) prevents the output MOSFET
from turning on until VIN exceeds approximately 2.5V. Under-
voltage detection functions only when the switch is enabled.
MIC2026/2076 Micrel
MIC2026/2076 12 February 1, 2001
Applications Information
Supply Filtering
A 0.1µF to 1µF bypass capacitor positioned close to VIN and
GND of the device is strongly recommended to control supply
transients. Without a bypass capacitor, an output short may
cause sufficient ringing on the input (from supply lead induc-
tance) to damage internal control circuitry.
Printed Circuit Board Hot-Plug
The MIC2026/76 are ideal inrush current-limiters for hot plug
applications. Due to the integrated charge pump, the
MIC2026/76 presents a high impedance when off and slowly
becomes a low impedance as it turns on. This “soft-start”
feature effectively isolates power supplies from highly ca-
pacitive loads by reducing inrush current. Figure 3 shows how
the MIC2076 may be used in a card hot-plug application.
In cases of extremely large capacitive loads (>400µF), the
length of the transient due to inrush current may exceed the
delay provided by the integrated filter. Since this inrush
current exceeds the current-limit delay specification, FLG will
be asserted during this time. To prevent the logic controller
from responding to FLG being asserted, an external RC filter,
as shown in Figure 4, can be used to filter out transient FLG
assertion. The value of the RC time constant should be
selected to match the length of the transient, less tD(min) of the
MIC2026/76.
Universal Serial Bus (USB) Power Distribution
The MIC2026/76 is ideally suited for USB (Universal Serial
Bus) power distribution applications. The USB specification
defines power distribution for USB host systems such as PCs
and USB hubs. Hubs can either be self-powered or bus-
powered (that is, powered from the bus). Figure 5 shows a
typical USB Host application that may be suited for mobile PC
applications employing USB. The requirement for USB host
systems is that the port must supply a minimum of 500mA at
an output voltage of 5V ±5%. In addition, the output power
delivered must be limited to below 25VA. Upon an overcurrent
condition, the host must also be notified. To support hot-plug
events, the hub must have a minimum of 120µF of bulk
capacitance, preferably low ESR electrolytic or tantulum.
Please refer to Application Note 17 for more details on
designing compliant USB hub and host systems.
For bus-powered hubs, USB requires that each downstream
port be switched on or off under control by the host. Up to four
downstream ports each capable of supplying 100mA at 4.4V
minimum are allowed. In addition, to reduce voltage droop on
the upstream VBUS, soft-start is necessary. Although the hub
can consume up to 500mA from the upstream bus, the hub
must consume only 100mA max at start-up, until it enumer-
ates with the host prior to requesting more power. The same
requirements apply for bus-powered peripherals that have no
downstream ports. Figure 6 shows a bus-powered hub.
ENA OUTA
FLGA
FLGB GND
OUTB
IN
18
27
36
5
USB
Controller
ENB
4
USB Peripheral
Cable
to "Hot"
Receptacle
C
BULK
GND
V
BUS
4.7
µF
USB
Function
USB
Function
C
BULK
MIC2026-2BM
Figure 3. Hot-Plug Application
10k
V+
MIC2026
EN OUTA
FLGA
FLGB GND
ENB OUTB
IN
18
27
36
45
OVERCURRENT
Logic Controller
R
C
Figure 4. Transient Filter
February 1, 2001 13 MIC2026/2076
MIC2026/2076 Micrel
ENA OUTA
FLGA IN
FLGB GND
ENB OUTB
ON/OFF
OVERCURRENT
OVERCURRENT
ON/OFF
MIC2026-23.3V USB Controller
V
CC
5.0V
0.1µF V
BUS
D+
D–
GND
Data
(Two Pair)
V
BUS
D+
D–
GND
USB
Port 2
USB
Port 1
10k
MIC5207-3.3
IN OUT
GND
47µF
47µF
Ferrite
Beads
4.50V to 5.25V
Upstream V
BUS
100mA max.
V
BUS
D+
D–
GND
Data
1µF 1µF
10k
VIN
to USB
Controller
Figure 5. USB Two-Port Host Application
ENA OUTA
FLGA IN
FLGB GND
ENB OUTB
ON/OFF
OVERCURRENT
OVERCURRENT
ON/OFF
MIC2026-23.3V USB Controller
0.1µF VBUS
D+
D–
GND
Data
(Two Pair)
VBUS
D+
D–
GND
USB
Port 2
USB
Port 1
10k
MIC5207-3.3
IN OUT
GND
47µF
47µF
Ferrite
Beads
4.50V to 5.25V
Upstream VBUS
VBUS
D+
D–
GND
Data
1µF 1µF
10k
VIN
to USB
Controller
1.5k 2%
Figure 6. USB Two-Port Bus-Powered Hub
MIC2026/2076 Micrel
MIC2026/2076 14 February 1, 2001
Package Information
45°
0°–8°
0.244 (6.20)
0.228 (5.79)
0.197 (5.0)
0.189 (4.8) SEATING
PLANE
0.026 (0.65)
MAX)
0.010 (0.25)
0.007 (0.18)
0.064 (1.63)
0.045 (1.14)
0.0098 (0.249)
0.0040 (0.102)
0.020 (0.51)
0.013 (0.33)
0.157 (3.99)
0.150 (3.81)
0.050 (1.27)
TYP
PIN 1
DIMENSIONS:
INCHES (MM)
0.050 (1.27)
0.016 (0.40)
8-Lead SOP (M)
0.380 (9.65)
0.370 (9.40)
0.135 (3.43)
0.125 (3.18)
PIN 1
DIMENSIONS:
INCH (MM)
0.018 (0.57)
0.100 (2.54)
0.013 (0.330)
0.010 (0.254)
0.300 (7.62)
0.255 (6.48)
0.245 (6.22)
0.380 (9.65)
0.320 (8.13)
0.0375 (0.952)
0.130 (3.30)
8-Pin DIP (N)
February 1, 2001 15 MIC2026/2076
MIC2026/2076 Micrel
MIC2026/2076 Micrel
MIC2026/2076 16 February 1, 2001
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131 USA
TEL + 1 (408) 944-0800 FAX + 1 (408) 944-0970 WEB http://www.micrel.com
This information is believed to be accurate and reliable, however no responsibility is assumed by Micrel for its use nor for any infringement of patents or
other rights of third parties resulting from its use. No license is granted by implication or otherwise under any patent or patent right of Micrel Inc.
© 2001 Micrel Incorporated