MIC2026-1BM TR - Micrel Semiconductor, Inc.

February 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

ON/OFF

MIC2026-2

Logic Controller

2.7V to 5.5V

0.1µF

VIN Load

Load

CONT.

10k

Features

•140mΩ maximum on-resistance per channel

•2.7V to 5.5V operating range

•500mA minimum continuous current per channel

•Short-circuit protection with thermal shutdown

•Thermally isolated channels

•Fault status flag with 3ms filter

eliminates false assertions

•Undervoltage 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

MIC2026/2076 Micrel

MIC2026/2076 2 February 2001

Ordering Information

Part Number Enable Temperature Range Package

MIC2026-1BM Active High –40°C to +85°C 8-lead SOP

MIC2026-2BM Active Low –40°C to +85°C 8-lead SOP

MIC2026-1BN Active High –40°C to +85°C 8-pin DIP

MIC2026-2BN Active Low –40°C to +85°C 8-pin DIP

MIC2076-1BM Active High –40°C to +85°C 8-lead SOP

MIC2076-2BM Active Low –40°C to +85°C 8-lead SOP

MIC2076-1BN Active High –40°C to +85°C 8-pin DIP

MIC2076-2BN Active Low –40°C to +85°C 8-pin DIP

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

OUTA

GND

OUTB

ENA

FLGA

FLGB

ENB

MIC2026/76

8-Lead SOP (BM)

8-Pin DIP (BN)

February 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”1.15 4.9 ms

tOFF Output Turnoff Delay RL = 10Ω, CL = 1µF, see “Timing Diagrams”35 100 µs

tFOutput Turnoff 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 low 3 ms

Undervoltage Lockout VIN rising 2.2 2.4 2.7 V

Threshold VIN falling 2.0 2.15 2.5 V

Absolute Maximum 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 2001

Symbol Parameter Condition Min Typ Max Units

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

OUT

Timing Diagrams

90%

VOUT

10%

90%

10%

tRtF

Output Rise and Fall Times

50%

90%

OUT

10%

OFF

Active-Low Switch Delay Times (MIC20x6-2)

50%

90%

OUT

10%

OFF

Active-High Switch Delay Times (MIC20x6-1)

February 2001 5 MIC2026/2076

MIC2026/2076 Micrel

100

120

140

160

180

-40 -20 0 20 40 60 80 100

CURRENT (µA)

TEMPERATURE (°C)

Supply On-Current

vs. Temperature

3.3V

100

120

140

160

-40 -20 0 20 40 60 80 100

ON-RESISTANCE (mΩ)

TEMPERATURE (°C)

On-Resistance

vs. Temperature

3.3V

IOUT = 500mA

-40 -20 0 20 40 60 80 100

RISE TIME (ms)

TEMPERATURE (°C)

Turn-On Rise Time

vs. Temperature

RL=10Ω

CL=1µF

VIN = 5V

VIN = 3.3V

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

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

IOUT = 500mA

+85°C

+25°C

-40°C

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

RL=10Ω

CL=1µF

+85°C

+25°C

-40°C

200

400

600

800

1000

-40 -20 0 20 40 60 80 100

CURRENT LIMIT (mA)

TEMPERATURE (°C)

Short-Circuit Current-Limit

vs. Temperature

VIN = 3.3V

VIN = 5V

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

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

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

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

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 2001

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

-40 -20 0 20 40 60 80 100

DELAY TIME (ms)

TEMPERATURE (°C)

Flag Delay

vs. Temperature

VIN = 3.3V

VIN = 5V

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

3.3V

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

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

0.02

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

0.5

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 2001 7 MIC2026/2076

MIC2026/2076 Micrel

Functional Characteristics

UVLO—VIN Rising

(MIC2026-1)

TIME (10ms/div.)

IOUT

(100mA/div.) VIN

(2V/div.)

VOUT

(2V/div.) VFLG

(2V/div.)

VEN = VIN

CL = 57µF

RL = 35Ω

2.4V

UVLO—VIN Falling

(MIC2026-1)

TIME (100ms/div.)

IOUT

(100mA/div.) VIN

(2V/div.)

VOUT

(5V/div.) VFLG

(2V/div.)

VEN = VIN

CL = 57µF

RL = 35Ω

2.2V

Turn-On/Turnoff

(MIC2026-1)

TIME (10ms/div.)

IOUT

(200mA/div.) VEN

(10V/div.)

VOUT

(5V/div.) VFLG

(5V/div.)

VIN = 5V

CL = 147µF

RL = 35Ω

712mA

(Inrush Current)

140mA

Turn-On

(MIC2026-1)

TIME (500µs/div.)

IOUT

(200mA/div.) VEN

(10V/div.)

VOUT

(5V/div.) VFLG

(5V/div.)

VIN = 5V

CL = 147µF

RL = 35Ω

140mA

Turnoff

(MIC2026-1)

TIME (5ms/div.)

IOUT

(200mA/div.) VEN

(10V/div.)

VOUT

(5V/div.) VFLG

(5V/div.)

VIN = 5V

CL = 147µF

RL = 35Ω

140mA

Enabled Into Short

(MIC2026-1)

TIME (500µs/div.)

IOUT

(500mA/div.) VEN

(10V/div.)

VOUT

(5V/div.) VFLG

(5V/div.)

VIN = 5V

3.1ms (tD)

700mA

MIC2026/2076 Micrel

MIC2026/2076 8 February 2001

Inrush Current Response

(MIC2026-1)

TIME (1ms/div.)

IOUT

(200mA/div.) VEN

(10V/div.)

VFLG

(5V/div.)

VIN = 5V

RL = 31Ω

CL = 10µF

CL = 110µFCL = 210µF

CL = 310µF

Current-Limit Response

(Ramped Load–MIC2026-1)

TIME (100ms/div.)

IOUT

(500mA/div.) VIN

(10V/div.)

VOUT

(5V/div.) VFLG

(10V/div.)

VIN = 5V

CL = 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.)

IOUT

(2A/div.) VEN

(10V/div.)

VOUT

(5V/div.) VFLG

(5V/div.)

VIN = 5V

CL = 47µF

RL = stepped short

800mA

Current-Limit Response

(MIC2026-1)

TIME (50µs/div.)

IOUT

(5A/div.) VOUT

(5V/div.)

VIN = 5V

CL = 0

RL = stepped short

Short-Circuit (800mA)

Independent Thermal Shutdown

(MIC2026-1)

TIME (100ms/div.)

IOUTB

(500mA/div.) VENB

(10V/div.)

VFLGB

(5V/div.) VFLGA

(5V/div.)

VOUTA = No Load

(No Thermal Shutdown)

Thermal Shutdown

Independent Thermal Shutdown

(MIC2026-1)

TIME (100ms/div.)

IOUTA

(500mA/div.) VENA

(10V/div.)

VFLGB

(5V/div.) VFLGA

(5V/div.)

VOUTB = No Load

(No Thermal Shutdown)

Thermal Shutdown

February 2001 9 MIC2026/2076

MIC2026/2076 Micrel

Thermal Shutdown

(MIC2076-2—Output Latched Off)

No Load

TIME (2.5s/div.)

IOUTB

(500mV/div.) VOUT

(5V/div.) VFLG

(10V/div.)

VIN = 5V

CL = 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.)

IOUT

(500mA/div.) VEN

(10V/div.)

VOUT

(5V/div.) VFLG

(5V/div.)

VIN = 5V

CL = 47µF

Load Removed

(Output Reset)

Output

Latched Off

Thermal

Shutdown

Ramp Load

to Short

Independent Thermal Shutdown

(MIC2076-2)

TIME (2.5s/div.)

IOUTA

(500mA/div.) VFLGA

(5V/div.) VFLGB

(5V/div.)

VIN = 5V

CL = 47µF

VENB = 0V

VENA = 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.)

IOUTB

(500mA/div.) VFLGA

(5V/div.) VFLGB

(10V/div.)

VIN = 5V

CL = 47µF

VENB = 0V

VENA = 0V

Output Reset

Load

Removed

No Thermal Shutdown on Channel A

Thermal

Shutdown

RL = 0 No

Load

MIC2026/2076 Micrel

MIC2026/2076 10 February 2001

Block Diagram

1.2V

REFERENCE

THERMAL

SHUTDOWN

CHARGE

PUMP

OUTB

UVLO

GATE

CONTROL

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 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 MOS-

FET 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.

OUT

Short-Circuit Fault

Thermal

Shutdown

Reached

Load and Fault Removed

(Output Reset)

FLG

LIMIT

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.

Undervoltage Lockout

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 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

USB

Controller

ENB

USB Peripheral

Cable

to "Hot"

Receptacle

BULK

GND

BUS

4.7

µF

USB

Function

USB

Function

BULK

MIC2026-2BM

Figure 3. Hot-Plug Application

10k

V+

MIC2026

EN OUTA

FLGA

FLGB GND

ENB OUTB

OVERCURRENT

Logic Controller

Figure 4. Transient Filter

February 2001 13 MIC2026/2076

MIC2026/2076 Micrel

ENA OUTA

FLGA IN

FLGB GND

ENB OUTB

ON/OFF

OVERCURRENT

ON/OFF

MIC2026-23.3V USB Controller

5.0V

0.1µF V

BUS

D+

D–

GND

Data

(Two Pair)

BUS

D+

D–

GND

USB

Port 2

USB

Port 1

10k

MIC5207-3.3

IN OUT

GND

47µF

Ferrite

Beads

4.50V to 5.25V

Upstream V

BUS

100mA max.

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

ON/OFF

MIC2026-23.3V USB Controller

0.1µF V

BUS

D+

D–

GND

Data

(Two Pair)

BUS

D+

D–

GND

USB

Port 2

USB

Port 1

10k

MIC5207-3.3

IN OUT

GND

47µF

Ferrite

Beads

4.50V to 5.25V

Upstream V

BUS

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 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 2001 15 MIC2026/2076

MIC2026/2076 Micrel

MIC2026/2076 16 February 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.