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MIC2526
Micrel
MIC2526
Dual USB Power Control Switch Not Recommended for New Designs
Refer to MIC2026
General Description
The MIC2526 is a dual integrated high-side power switch with independent enable and flag functions, optimized for selfpowered and bus-powered Universal Serial Bus (USB) applications. Few external components are necessary to satisfy USB requirements. The MIC2526 satisfies the following USB requirements: each switch channel supplies up to 500mA as required by USB downstream devices; the switch's low on-resistance meets USB voltage drop requirements; fault current is limited to typically 750mA, well below the UL 25VA safety requirements; and a flag output is available to indicate fault conditions to the local USB controller. Soft start eliminates the momentary voltage drop on the upstream port that may occur when the switch is enabled in bus-powered applications. Additional features include thermal shutdown to prevent catastrophic switch failure from high-current loads, undervoltage lockout (UVLO) to ensure that the device remains off unless there is a valid input voltage present, and 3.3V and 5V logic compatible enable inputs. The MIC2526 is available in active-high and active-low versions in 8-pin DIP and SOIC packages.
Features
* * * * * * * * * * * * * * * * * * * * Compliant to USB specifications UL Recognized Component 2 independent switches 3V to 5.5V input 500mA minimum continuous load current per port 140m maximum on-resistance 1.25A maximum short circuit current limit Individual open-drain fault flag pins 110A typical on-state supply current 1A typical off-state supply current Output can be forced higher than input (off-state) Thermal shutdown 2.4V typical undervoltage lockout (UVLO) 1ms turn-on (soft-start) and fast turnoff Active-high or active-low enable versions 8-pin SOIC and DIP packages USB host and self-powered hubs USB bus-powered hubs Hot plug-in power supplies Battery-charger circuits
Applications
Typical Application
VCC 5.0V 10k 4.50V to 5.25V Upstream VBUS 100mA max. VBUS D+ D- GND 1F 10k MIC5207-3.3 IN OUT GND 1F 3.3V USB Controller VIN ON/OFF OVERCURRENT OVERCURRENT ON/OFF 100k 100k MIC2526-2 ENA FLGA FLGB ENB OUTA IN GND OUTB 47F Data Data (Two Pair) to USB Controller 47F 0.1F VBUS D+ D- GND USB Port 2
Ferrite Beads VBUS D+ D- GND USB Port 1
2-Port USB Self-Powered Hub
UL Recognized Component Micrel, Inc. * 1849 Fortune Drive * San Jose, CA 95131 * USA * tel + 1 (408) 944-0800 * fax + 1 (408) 944-0970 * http://www.micrel.com
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MIC2526
MIC2526
Micrel
Ordering Information
Part Number MIC2526-1BM MIC2526-2BM MIC2526-1BN MIC2526-2BN Enable Active High Active Low Active High Active Low Temperature Range -40C to +85C -40C to +85C -40C to +85C -40C to +85C Package 8-Pin SOIC 8-Pin SOIC 8-pin DIP 8-pin DIP
Pin Configuration
MIC2526
ENA FLGA FLGB ENB 1 2 3 4 8 7 6 5 OUTA IN GND OUTB
8-Pin SOIC (M) 8-Pin DIP (N)
MIC2526 (ENA) 1 (FLGA) 2 (FLGB) 3 (ENB) 4
LOGIC, CHARGE PUMP LOGIC, CHARGE PUMP
8 (OUTA) 7 (IN) 5 (OUTB)
6 (GND)
Pin Description
Pin Number 1/4 2/3 6 7 8/5 Pin Name EN(A/B) FLG(A/B) GND IN OUT(A/B) Pin Function Enable (Input): Logic-compatible enable input. High input > 2.1V typical. Low input <1.9V typical (-1 active high, -2 active low). Do not float. Fault Flag (Output): Active-low, open-drain output. Indicates overcurrent, UVLO, and thermal shutdown. Ground: Supply return. Supply Input: Output MOSFET drain. Also supplies IC's internal circuitry. Connect to positive supply. Switch Output: Output MOSFET source. Typically connect to switched side of load.
MIC2526
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MIC2526
Micrel
Absolute Maximum Ratings (Note 1)
Supply Voltage (VIN) ..................................................... +6V Fault Flag Voltage (VFLG) .............................................. +6V Fault Flag Current (IFLG) ............................................ 50mA Output Voltage (VOUT) .................................................. +6V Output Current (IOUT) ............................... Internally Limited Control Input (VEN) ......................................... -0.3V to 12V Storage Temperature (TS) ....................... -65C to +150C Lead Temperature (Soldering 5 sec.) ....................... 260C ESD Rating, Note 3 ...................................................... 2kV
Operating Ratings (Note 2)
Supply Voltage (VIN) ...................................... +3V to +5.5V Ambient Operating Temperature (TA) ........ -40C to +85C Thermal Resistance SOIC (JA) ......................................................... 120C/W DIP(JA) ............................................................. 130C/W
Electrical Characteristics
VIN = +5V; TA = 25C; unless noted. Parameter Supply Current Condition Note 4, switch off, OUT = open Note 4, all switches on, OUT = open Enable Input Threshold low-to-high transition high-to-low transition, Note 4 Enable Input Current Enable Input Capacitance Switch Resistance VIN = 5V, IOUT = 500mA, each switch VIN = 3.3V, IOUT = 500mA, each switch Output Turn-On Delay Output Turn-On Rise Time Output Turnoff Delay Output Turnoff Fall Time Output Leakage Current Continuous Load Current Short-Circuit Current Limit Current-Limit Threshold Overtemperature Shutdown Threshold Error Flag Output Resistance RL = 10 each output RL = 10 each output RL = 10 each output RL = 10 each output each output (output disabled) each output each output (enable into load), VOUT = 4.0V ramped load applied to enabled output, VOUT 4.0V, Note 5 TJ increasing TJ decreasing VIN = 5V, IL = 10mA VIN = 3.3V, IL = 10mA Error Flag Off Current UVLO Threshold VFLAG = 5V VIN = increasing VIN = decreasing
Note 1. Note 2. Note 3. Note 4. Note 5. Exceeding the absolute maximum rating may damage the device. The device is not guaranteed to function outside its operating rating. Devices are ESD sensitive. Handling precautions recommended. Human body model, 1.5k in series with 100pF. Off is 0.8V and on is 2.4V for the MIC2526-1. Off is 2.4V and on is 0.8V for the MIC2526-2. The enable input has approximately 200mV of hysteresis. See control threshold charts. See "Functional Characteristics: Current-Limit Response" photo.
Min
Typ 0.75 110 2.1
Max 5 160 2.4
Units A A V V A pF
0.8 -1
1.9 0.01 1 100 140 0.5 1 1 1 20 20 10 140 180 1
VEN = 0V to 5.5V
m m ms ms s s A A
0.5 0.5 0.75 1.6 135 125 10 15 0.01 2.5 2.3 25 40 1 1.25 2.2
A A C C A V V
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MIC2526
MIC2526
Micrel
Typical Characteristics
VIN = 5V; TA = 25C; one switch section; unless noted.
Output On-Resistance vs. Supply Voltage
ON-RESISTANCE (m)
110 OUTPUT RESISTANCE (m)
140
Output On-Resistance vs. Temperature
THRESHOLD VOLTAGE (V)
3.0
UVLO Threshold Voltage vs. Temperature
120
100 Awaiting Full Characterization Data 90 RL = 44 T = 25C 80 3.0 3.5 4.0 4.5 5 SUPPLY VOLTAGE (V) 5.5
2.5
RISING
100
FALLING 2.0
80
RL = 44 VIN = 5V
60 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
1.5 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
250 SUPPLY CURRENT (A) 200 150 100 50
On-State Supply Current vs. Supply Voltage
SUPPLY CURRENT (A)
2.0
Off-State Supply Current vs. Supply Voltage
2.5 THRESHOLD VOLTAGE (V)
Control Threshold vs. Supply Voltage
1.5
2.0
VCTL RISING
1.0
1.5
0.5 SWITCH OFF 0 2 3 4 5 SUPPLY VOLTAGE (V) 6
VCTL FALLING
SWITCH ON 0 0 2 4 SUPPLY VOLTAGE (V) 6
1.0
2
3 4 SUPPLY VOLTAGE (V)
5
200 SUPPLY CURRENT (A) 175 150 125 100 75 50 25
On-State Supply Current vs. Temperature
SUPPLY CURRENT (A)
2.0
Off-State Supply Current vs. Temperature
2.5 ENABLE VOLTAGE (V)
Control Threshold vs. Temperature
1.5
2.0 VEN FALLING 1.5
VEN RISING
1.0
0.5 BOTH SWITCHES OFF 0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
BOTH SWITCHES ON
0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
VIN = 5V 1.0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
5 4 3 2 1
Output Rise Time vs. Temperature
1.0 0.8
Output Fall Time vs. Temperature
2.0 1.8
Current-Limit Threshold vs. Temperature
Awaiting Full Characterization Data
0.6 0.4 0.2
Awaiting Full Characterization Data
CURRENT (A)
TIME (ms)
TIME (s)
CURRENT LIMIT THRESHOLD 1.6 1.4 SHORT CIRCUIT CURRENT LIMIT 1.2 1.0 -25
0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
0 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
0 25 50 75 TEMPERATURE (C)
100
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Functional Characteristics
Input Voltage Response Turn-On, Turnoff Characteristics
2.6V (UVLO) Threshold
VFLG VOUT IOUT (200mA/div.)(5V/div.) (2V/div.)
VEN VOUT VFLG (2V/div.) (5V/div.) (5V/div.)
VIN (2V/div.)
IOUT (100mA/div.)
VEN = VIN RL = 35 CL = 15F
144mA RL = 35 CL = 10F TIME (2.5ms/div.)
TIME (100ns/div.)
Turn-On, Turnoff Characteristics
VEN VFLG (5V/div.) (5V/div.)
Short Circuit Response (Short Applied to Output)
VOUT (2V/div.)
IOUT (100mA/div.)
144mA RL = 35 CL = 150F TIME (2.5ms/div.)
VOUT (2V/div.)
VFLG (5V/div.)
IOUT (1A/div.)
Thermal Shutdown 0.95A Short Circuit Limiting TIME (250ms/div.)
Short Circuit Response (Enable into Short Circuit)
VEN (5V/div.) VOUT IOUT (1A/div.) (2V/div.) VFLG (5V/div.)
Thermal Shutdown 0.95A Short Circuit Limiting TIME (250ms/div.)
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MIC2526
Micrel
Short Circuit Transient Response (Short Applied to Output)
VOUT (5V/div.)
Current-Limit Response (Ramped Load)
VFLG (5V/div.)
2.76A
VOUT (2V/div.)
Current Limit Threshold
VFLG (5V/div.)
IOUT (1A/div.)
1A Current Limit
TIME (500s/div.)
IOUT (1A/div.)
1A Current Limit
TIME (1ms/div.)
Test Circuit
5V 10k 0.1F MIC2526 ENA FLGA FLGB ENB OUTA IN GND OUTB Ferrite Bead IOUT CL RL ILOAD (for Current Limit Response)
(1 output shown)
Functional Characteristics Test Circuit
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MIC2526
Micrel
Block Diagrams
FLGA
OUTA ENA CHARGE PUMP GATE CONTROL CURRENT LIMIT
OSC.
THERMAL SHUTDOWN
UVLO
1.2V REFERENCE
IN
CHARGE PUMP GATE CONTROL ENB
CURRENT LIMIT
OUTB FLGB
MIC2526 GND
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MIC2526
MIC2526
Micrel
Undervoltage Lockout UVLO (undervoltage lockout) prevents the output MOSFET from turning on until VIN exceeds approximately 2.5V. In the undervoltage state, the FLAG will be low. After the switch turns on, if the voltage drops below approximately 2.3V, UVLO shuts off the output MOSFET and signals fault flag. Undervoltage detection functions only when at least one switch is enabled. Current Sensing and Limiting The current-limit threshold is preset internally. The preset level prevents damage to the output MOSFET and external load but allows a minimum current of 0.5A through the output MOSFET of each channel. The current-limit circuit senses a portion of the output 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:
Functional Description
The MIC2526-1 and MIC2526-2 are dual high-side switches with active-high and active-low enable inputs, respectively. Fault conditions turn off or inhibit turn-on of one or more of the output transistors, depending upon the type of fault, and activate the open-drain error flag transistors making them sink current to ground. Input and Output IN (input) is the power supply connection to the logic circuitry and the drain of the output MOSFET. OUTx (output) is the source of its respective MOSFET. In a typical circuit, current flows through the switch from IN to OUT toward the load. If VOUT is greater than VIN when a switch is enabled, current will flow from OUT to IN since the MOSFET is bidirectional when on. 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 output is off. In this situation, the MIC2526 avoids undesirable current flow from OUT to IN. If VIN < 2.5V, UVLO disables both switches. Thermal Shutdown Thermal shutdown shuts off the affected output MOSFETs and signals all fault flags if the die temperature exceeds 135C. 10C of hysteresis prevents the switch from turning on until the die temperature drops to 125C. Overtemperature detection functions only when at least one switch is enabled. Current Limit Induced Thermal Shutdown Internal circuitry increases the output MOSFET on-resistance until the series combination of the MOSFET on-resistance and the load impedance limit current to typically 850mA. The increase in power dissipation, in most cases, will cause the MIC2526 to go into thermal shutdown, disabling affected channels. When this is undesirable, thermal shutdown can be avoided by externally responding to the fault and disabling the current limited channel before the shutdown temperature is reached. The delay between the flag indication of a current limit fault and thermal shutdown will vary with ambient temperature, board layout, and load impedance, but is typically several hundred milliseconds. The USB controller must therefore recognize a fault and disable the appropriate channel within this time. If the fault is not removed or the switch is not disabled within this time, then the device will enter into a thermal oscillation of about 2Hz. This does not cause any damage to the device. Refer to "Functional Characteristics: Thermal Shutdown Response."
Switch Enabled into Short Circuit If a switch is powered on or enabled into a heavy load or shortcircuit, the switch immediately goes into a constant-current mode, reducing the output voltage. The fault flag goes low until the load is reduced. See the "Functional Characteristics: Short Circuit Response, Enabled into Short Circuit" photo. Short Circuit Applied to Output When a heavy load is applied, a large transient current may flow until the current limit circuitry will respond. Once this occurs, the device limits current to less than the short-circuit current limit specification. See the "Short Circuit Transient Response, Short Applied to Output" graph. Current-Limit Response The MIC2526 current-limit profile exhibits a small foldback effect of approximately 500mA. Once this current-limit threshold is exceeded the device enters constant-current mode. This constant current is specified as the short circuit current limit in the "Electrical Characteristics" table. It is important to note that the MIC2526 will deliver load current up to the current-limit threshold which is typically 1.6A. Refer to "Functional Characteristics: Current-Limit Response" photo for details. Fault Flag FLG is an N-channel, open-drain MOSFET output. The faultflag is active (low) for one or more of the following conditions: undervoltage (while 2V < VIN < 2.7), current limit, or thermal shutdown. The flag output MOSFET is capable of sinking a 10mA load to typically 100mV above ground. Multiple FLG pins may be "wire NORed" to a common pull-up resistor.
MIC2526
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Soft Start The MIC2526 presents a high impedance when off, and slowly becomes a low impedance as it turns on. This reduces inrush current and related voltage drop that results from charging a capacitive load, satisfying the USB voltage droop requirements for bus-powered applications as shown in Figure 2. The soft start circuit shown in Figure 3 can be utilized to meet USB transient regulation specifications with large load capacitances (CBULK > 10uF). The MIC2526 will provide inrush current limiting for these applications. Transient Overcurrent Filter When the MIC2526 is enabled, large values of capacitance at the output of the device will cause inrush current to exceed the short circuit current-limit threshold of the device and assert the flag. The duration of this time will depend on the size of the output capacitance. Refer to the "Functional Characteristics" turn-on and turnoff behaviors for details. During the capacitance charging time, the device enters into constant-current mode. As the capacitance is charged, the current decreases below the short circuit current-limit threshold, and the flag will then be deasserted.
Applications Information
Supply Filtering A 0.1F to 1F bypass capacitor from IN to GND, located at 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 inductance) to damage internal control circuitry. Input or output transients must not exceed the absolute maximum supply voltage (VIN max = 6V) even for a short duration.
3.0V to 5.5V MIC2526 ENA FLGA FLGB ENB OUTA IN GND OUTB 0.1F to 1F
Figure 1. Supply Bypassing Enable Input EN must be driven logic high or logic low for a clearly defined input. Floating the input may cause unpredictable operation. EN should not be allowed to go negative with respect to GND.
USB Controller MIC2526-xBM VBUS
1 2 3
ENA FLGA FLGB ENB
OUTA IN GND OUTB
8 7 6 5
0.1F
CBULK
USB Host
4.7 F
Capacitive Load
4
GND Cable Bus Powered Hub Cable Downstream USB Device
Figure 2. Soft Start (Single Channel)
USB Controller MIC2526-2BM VBUS 4.7 F USB Hub
1 2 3 4
ENA FLGA FLGB ENB
OUTA IN GND OUTB
8 7 6 5
USB Function CBULK USB Function CBULK
GND Cable USB Peripheral
Figure 3. Inrush Current-Limit Application
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MIC2526
MIC2526
In USB applications, it is required that output bulk capacitance is utilized to support hot-plug events. When the MIC2526 is enabled, the flag may go active for about 1ms due to inrush current exceeding the current-limit setpoint. Additionally, during hot-plug events, inrush currents may also cause the flag to go active for 30s. Since these conditions are not valid overcurrent faults, the USB controller must ignore the flag during these events. To prevent this erroneous overcurrent reporting, a 1ms RC filter as shown in Figure 4 may be used. Alternatively, a 1ms debounce routine may be programmed into the USB logic controller, eliminating the need for the RC filter.
V+ USB Controller OVERCURRENT 0.1 F 10k
1
Micrel
MIC2526 ENA FLGA FLGB ENB OUTA IN GND OUTB
8 7 6 5
10k
2 3 4
Figure 4. Transient Filter
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Package Information
0.026 (0.65) MAX) PIN 1
0.157 (3.99) 0.150 (3.81)
DIMENSIONS: INCHES (MM)
0.050 (1.27) TYP
0.020 (0.51) 0.013 (0.33) 0.0098 (0.249) 0.0040 (0.102) 0-8 SEATING PLANE 45 0.010 (0.25) 0.007 (0.18)
0.064 (1.63) 0.045 (1.14)
0.197 (5.0) 0.189 (4.8)
0.050 (1.27) 0.016 (0.40) 0.244 (6.20) 0.228 (5.79)
8-Pin SOP (M)
PIN 1 DIMENSIONS: INCH (MM)
0.380 (9.65) 0.370 (9.40)
0.135 (3.43) 0.125 (3.18)
0.255 (6.48) 0.245 (6.22) 0.300 (7.62)
0.013 (0.330) 0.010 (0.254) 0.018 (0.57) 0.100 (2.54) 0.130 (3.30) 0.0375 (0.952) 0.380 (9.65) 0.320 (8.13)
8-Pin Plastic DIP (N)
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MIC2526
MIC2526
Micrel
MICREL INC. 1849 FORTUNE DRIVE SAN JOSE, CA 95131
TEL
USA
+ 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. (c) 2000 Micrel Incorporated
MIC2526
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February 2000

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