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MIC2536
Micrel
MIC2536
Dual USB Power Distribution Switch Preliminary Information
General Description
The MIC2536 is a cost-effective high-side power switch, with two independently controlled channels, optimized for buspowered Universal Serial Bus (USB) applications. Few external components are necessary to satisfy USB requirements. Each switch channel of the MIC2536 will supply up to 100mA as required for USB bus-powered downstream devices. Fault current is limited to typically 275mA by fast-acting currentlimit circuitry which minimizes voltage droop on the upstream port during fault conditions. A flag output with transient filter indicates fault conditions to the local USB controller but will ignore short flag signals resulting from inrush current during hot plug-in events. Soft start eliminates the momentary voltage droop on other ports that may occur when the switch is enabled in buspowered applications. Additional features include thermal shutdown to prevent catastrophic switch failure from highcurrent loads and 3.3V and 5V logic compatible enable inputs. The MIC2536 is available in active-high and active-low versions in 8-lead SOP and MSOP.
Features
* * * * * * * * * * * * * * * * * * * * * Compliant to USB specifications 2.7V to 5.5V operating range 150mA minimum continuous load current per channel 400m typical on-resistance Fast-acting short circuit protection with thermal shutdown Integrated filter eliminates false overcurrent flag assertions Individual open-drain fault flag pins with transient filter 3V/5V-compatible enable inputs Active-high (-1) and active-low (-2) versions Reverse-current blocking in off mode (no "body diode") Soft-start circuit 100A maximum on-state supply current <1A typical off-state supply current -40C to 85C operation USB keyboard bus-powered hubs USB bus-powered docking stations Note Book PCs PDAs General purpose power distribution applications PC board hot swap Inrush current-limiting
Applications
Typical Application
10k 4.50V to 5.25V Upstream VBUS 100mA max. VBUS D+ D- GND 4.7F 1.5k MIC5207-3.3 IN OUT GND 1F 10k 3.3V USB Controller VIN ON/OFF OVERCURRENT OVERCURRENT ON/OFF MIC2536-2 ENA FLGA FLGB ENB OUTA IN GND OUTB 63F 0.1F
Ferrite Beads VBUS D+ .01F D- GND USB Port 1
VBUS D+ .01F 63F D- GND Data (Two Pair) to USB Controller USB Port 2
Data
Typical Two-Port Bus-Powered Hub
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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MIC2536
MIC2536
Micrel
Ordering Information
Part Number MIC2536-1BM MIC2536-2BM MIC2536-1BMM MIC2536-2BMM 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-Lead SOP 8-Lead SOP 8-Lead MSOP 8-Lead MSOP
Pin Configuration
MIC2536-x
ENA FLGA FLGB ENB 1 2 3 4 8 7 6 5 OUTA IN GND OUTB
8-Lead SOP (M) 8-Lead MSOP (MM)
Pin Description
Pin Number 1 2 Pin Name ENA FLGA Pin Function Enable A (Input): Channel A control input. Active high (-1) or active low (-2) input. Flag A: (Output): Channel A open-drain fault flag output. Indicates overcurrent or thermal shutdown conditions. Overcurrent conditions must last longer than tD in order to assert FLG. Flag B (Output): Channel B open-drain fault flag output. Indicates overcurrent or thermal shutdown conditions. Overcurrent conditions must last longer than tD in order to assert FLG. Enable B (Input): Channel B control input. Active high (-1) or active low (-2) input. Output B: Channel B switch output. Ground Positive Switch and Logic Supply Input Output A: Channel A switch output.
3
FLGB
4 5 6 7 8
ENB OUTB GND IN OUTA
MIC2536
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MIC2536
Micrel
Absolute Maximum Ratings (Note 1)
Supply Voltage (VIN) ..................................................... +6V Fault Flag Voltage (VFLG) .............................................. +6V Fault Flag Current (IFLG) ............................................ 25mA Output Voltage (VOUT) .................................................. +6V Output Current (IOUT) ............................... Internally Limited Control Input (VEN) ................................... -0.3V to VIN +2V Storage Temperature (TS) ....................... -65C to +150C Lead Temperature (Soldering 5 sec.) ....................... 260C ESD Rating, Note 3 ...................................................... 1kV
Operating Ratings (Note 2)
Supply Voltage (VIN) ................................... +2.7V to +5.5V Ambient Operating Temperature (TA) ........ -40C to +85C Thermal Resistance SOP (JA) .......................................................... 160C/W MSOP (JA) ....................................................... 206C/W
Electrical Characteristics
VIN = +5V; TA = 25C, bold values indicate -40C TA +85C; unless noted Parameter Supply Current Condition both switches off, OUTA-B = open, Note 4 both switches on, OUTA-B = open, Note 4 Enable Input Threshold low-to-high transition, Note 4 high-to-low transition, Note 4 Enable Input Current Enable Input Capacitance Switch Resistance Output Turn-On Delay, tON Output Turn-On Rise Time, tR Output Turnoff Delay, tOFF Output Turnoff Fall Time, tF Output Leakage Current Current Limit Threshold Short Circuit Current Limit Current Limit Response Flag Response Delay, tD Overtemperature Shutdown Threshold Error Flag Output Resistance VEN = 0V to 5.5V Note 5 single switch, IOUT = 100mA RL = 50, CL = 1F RL = 50, CL = 1F RL = 50, CL = 1F RL = 50, CL = 1F each output (switch off) ramped load applied to enable output each output (enabled into load), VOUT = 0V VOUT = 0V to IOUT = ILIMIT (short applied to output), Note 5 VIN = 5V, apply VOUT = 0V until FLG low VIN = 3.3V, apply VOUT = 0V until FLG low TJ increasing, Note 5 TJ decreasing, Note 5 VIN = 5V, IL = 10mA VIN = 3.3V, IL = 10mA Error Flag Off Current
Note 1. Note 2. Note 3. Note 4. Note 5.
Min
Typ 0.75 60 1.7
Max 5 100 2.4
Units A A V V A pF
0.8
1.5 0.01 1 400 1.5 1.4 130 115 1 10 500 700 1
m ms ms s s A mA mA s
150
275 10
400
5
13 13 135 125 10 15 0.01
20
ms ms C C A
20 30 1
VFLAG = 5V
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 MIC2536-1. Off is 2.4V and on is 0.8V for the MIC2536-2. The enable input has approximately 200mV of hysteresis. Guaranteed by design. Not production tested.
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MIC2536
MIC2536
Micrel
Test Circuit
VOUT Device Under OUT Test RL CL
Functional Characteristics Test Circuit
Timing Diagrams
tr 90% VOUT 10% 10% 90% tf
Output Rise and Fall Times
VEN
50% tOFF tON
VOUT
90% 10%
Active-High Switch Delay Times (MIC2536-1)
VEN
50% tOFF tON
VOUT
90% 10%
Active-Low Switch Delay Times (MIC2536-2)
MIC2536
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MIC2536
Micrel
Functional Characteristics
Turn-On / Turnoff (MIC2536-1)
VFLG VEN (5V/div) (10V/div) VFLG VEN (5V/div) (10V/div)
Turn-On (MIC2536-1)
VOUT IOUT (100mA/div) (5V/div)
VOUT (5V/div)
VIN = 5V CIN = 4.7F
RL = 35 CL = 10F
VIN = 5V CIN = 4.7F
RL = 50 CL = 1F
IOUT (100mA/div)
Time (1ms/div)
Time (1ms/div)
Turnoff (MIC2536-1)
VFLG VEN (5V/div) (10V/div) VFLG VEN (5V/div) (10V/div)
Turn-On (MIC2536-1)
VOUT (5V/div)
VOUT IOUT (100mA/div) (5V/div)
VIN = 5V CIN = 4.7F
RL = 35 CL = 10F
VIN = 5V CIN = 4.7F
RL = 35 CL = 47F || 10F
(output current limited)
IOUT (100mA/div)
Time (1ms/div)
Time (1ms/div)
Turnoff (MIC2536-1)
VFLG VEN (5V/div) (10V/div) VFLG VEN (5V/div) (10V/div)
Enabled Into Short Circuit (MIC2536-1)
VIN = 5V CIN = 4.7F
RL = 35 CL = 47F || 10F
tD
VOUT (5V/div)
IOUT (100mA/div)
VOUT IOUT (200mA/div) (5V/div)
VIN = 5V CIN = 4.7F
OUT = GND CL = 0
Time (5s/div)
Time (10ms/div)
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MIC2536
MIC2536
Micrel
Ramped Into Short Circuit (MIC2536-1)
VFLG VEN (5V/div) (10V/div) VFLG VEN (5V/div) (10V/div)
Inrush Current (MIC2536-1)
VIN = 5V CIN = 4.7F RL = 0
VOUT (5V/div)
CL = 110F CL = 210F CL = 310F CL = 410F
Thermal Shutdown
IOUT (200mA/div)
IOUT (100mA/div)
VIN = 5V CIN = 4.7F RL = 35
CL = 10
Time (100ms/div)
Time (5s/div)
Current-Loop Response (MIC2536-1)
output = open
VOUT (5V/div)
output = ground
IOUT (1A/div)
VEN = 5V VIN = 5V CIN = 4700F
CL = 47F
Time (5s/div)
MIC2536
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MIC2536
Micrel
Block Diagram
FLGA
DELAY ENA CHARGE PUMP GATE CONTROL CURRENT LIMIT
OUTA
OSC.
THERMAL SHUTDOWN
1.2V REFERENCE
IN
CHARGE PUMP GATE CONTROL ENB
CURRENT LIMIT
DELAY
OUTB
FLGB MIC2536 GND
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MIC2536
MIC2536
Micrel
Equations that can be used to calculate power dissipation and die temperature are found below: Calculation of power dissipated by each channel can be accomplished by the following equation: PD = RDS(on) x (IOUT)2 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 x JA + TA where: Tj = junction temperature TA = ambient temperature JA = is the thermal resistance of the package 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 150mA 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 the following three scenarios: Switch Enabled into Short Circuit If a switch is enabled into a heavy load or short circuit, the switch immediately goes into a constant-current mode, reducing the output voltage. The FLG is asserted indicating an overcurrent condition. Short Circuit Applied to Output When a heavy load or short circuit is applied to an enabled switch, a large transient current may flow until the currentlimit circuitry responds. Once this occurs, the device limits current to less than the maximum short-circuit current-limit specification. Current-Limit Response Ramped Load The MIC2536 current-limit profile exhibits a small foldback effect of approximately 100mA. Once this current-limit threshold is exceeded the device enters constant-current mode. This constant current is specified as the short-circuit currentlimit in the "Electrical Characteristics" table. It is important to note that the MIC2536 will deliver load current up to the current-limit threshold before entering current-limited operation. Fault Flag FLGx is an open-drain N-channel MOSFET output. Fault flags are active (low) for current-limit or thermal shutdown. In the case where an overcurrent condition occurs, 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. 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 threshold. The flag response delay time is typically 12ms. 8 March 2000
Functional Description
The MIC2536-1 and MIC2536-2 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 each output MOSFET. OUTx (output) is the source of each respective MOSFET. In a typical circuit, current flows through the switch from IN to OUTx toward the load. If VOUT is greater than VIN, current will flow from OUT to IN during an on-condition since the MOSFET 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 (VOUTx > VIN) when the output is disabled. In this situation, the MIC2536 prevents reverse current flow. Thermal Shutdown Each output MOSFET has its own thermal sensor. If either or both channels reach 135C, affected channel(s) will be shut down and flag(s) asserted. 10C of hysteresis prevents the switches from turning on until the die temperature drops to 125C. Overtemperature detection functions only when at least one switch is enabled. The MIC2536 will automatically reset its output when the die temperature cools to approximately 125C. The MIC2536 output and FLG signal will continue to cycle on and off until the device is disabled or the fault is removed. Depending on PCB layout, package, ambient temperature, etc., it may take several hundred milliseconds from the occurrence of the fault to the output MOSFET being shut off. Delay to reach thermal shutdown will be shortest with a dead short on the output. 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 limits output current to approximately 275mA. The resulting increase in power dissipation may cause the shorted channel to go into thermal shutdown. In addition, even though individual channels are thermally isolated, it is possible they may shut down when an adjacent channel is shorted. 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 seconds. The USB controller must therefore recognize a fault and disable the appropriate channel within this time. Power Dissipation Power dissipation depends on several factors such as the load, PCB layout, ambient temperature and package type. MIC2536
MIC2536
Micrel
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. Printed Circuit Board Hot-Plug The MIC2536 is an ideal inrush current-limiter for hot-plug applications. Due to the integrated charge pump, the MIC2536 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 capacitive loads by reducing inrush current. Figure 2 shows how the MIC2536 may be used in a hot-plug card application. Overcurrent Transients The MIC2536 incorporates an internal circuit designed to prevent FLG from being asserted due to transient inrush current. Overcurrent events <12ms (typ.) will not assert FLG. In case of large capacitive loads (i.e., >430F), 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 3, 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, minus flag tD.
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.
VIN 2.7V to 5.5V MIC2536 ENA FLGA FLGB ENB OUTA IN GND OUTB 0.1F to 1F
Figure 1. Supply Bypassing
MIC2536-2 VCC to "Hot" Receptacle 0.1 F
1 2 3 4
EN FLGA FLGB ENB
OUTA IN GND OUTB
8 7 6 5
Backend Function
GND Adaptor Card
CBULK
Figure 2. Hot-Plug Card Application
V+ Logic Controller OVERCURRENT 10k
1
MIC2536 EN FLGA FLGB ENB OUTA IN GND OUTB
8 7 6 5
R C
2 3 4
Figure 3. Transient Filter
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MIC2536
MIC2536
Universal Serial Bus (USB) Power Distribution Applications The MIC2536 is ideally suited for USB (Universal Serial Bus) power distribution applications. 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 additon, to reduce voltage droop on the upstream bus the hub must consume only 100mA max at start-up until it enumerates with the host prior to requesting more power. The same requirements apply for bus-powered peripherals that have no downstream ports. Figure 4 shows a two-port bus-powered hub. Bus-Powered Hub Port Switching The USB Specification requires that bus-powered hubs implement port switching on either a ganged or individual basis. The specific implementation must be reported via the Hub Descriptor Status Register. Individual port switching has advantages in that a fault on one port will not prevent the other ports from operating correctly. In addition, a soft-start circuit must be included in order to reduce inrush currents when the switch is enabled. To meet this requirement, the MIC2536 has been designed to slowly ramp its output. Suspend Current Universal Serial Bus Specification places a maximum suspend current requirement of 500A on devices. For hubs, Universal Serial Bus Specification Revision 1.1 clarifies this issue. Revision 1.1, section 7.2.3, stipulates that the maximum suspend current for a configured hub is 2.5mA. This number is derived by allocating 500A for up to four downstream ports plus 500A for the hub's internal functions. A nonconfigured hub is considered a low-power device and
Micrel
may not consume more than 500A. In a nonconfigured state all downstream devices will be switched off. In most cases, a nonconfigured hub is not a practical state for the system. Therefore, the 2.5mA specification is the applicable target specification for the suspend state. In a bus-powered hub with less than 4 ports, the hub may use the additional current for internal functions. The 500A worst case suspend current must be further divided among the data port termination resistors and internal functions. The termination resistors will consume 3.6V / (16.5K - 5%) = 230A. This leaves only 270A for internal functions. Assuming 100A as the maximum USB controller suspend current, 170A remains for the rest of the system. The MIC2536 will consume 100A maximum, leaving a margin of 70A. USB Voltage Regulation USB specifications require a minimum downstream voltage supply of 4.40V from a bus-powered hub port (See Application Note 17 for details). The USB specification allows for a 100mV drop across the hub, leaving 250mV for PCB, upstream cable, and connector resistance. Therefore, the onresistance of the switch for each port, not including PCB resistance, must be <100mV / 100mA = 1. The MIC2536 has a maximum on-resistance of 700m, which easily satisfies this requirement. Overcurrent Indication The USB Specification does not require bus-powered hubs to report overcurrent conditions to the host, since the hub is already current-limited at the upstream port. However, if it is desired to report overcurrent, the Hub Descriptor Status Register must be programmed to indicate this. The MIC2536 provides a flag output for this application.
10k 4.50V to 5.25V Upstream VBUS 100mA max. VBUS D+ D- GND 4.7F 1.5k MIC5207-3.3 IN OUT GND 1F 10k 3.3V USB Controller VIN ON/OFF OVERCURRENT OVERCURRENT ON/OFF MIC2536-2 ENA FLGA FLGB ENB OUTA IN GND OUTB 63F 0.1F
Ferrite Beads VBUS D+ .01F D- GND USB Port 1
VBUS D+ .01F 63F D- GND Data (Two Pair) to USB Controller USB Port 2
Data
Figure 4. USB Two-Port Bus-Powered Hub
MIC2536
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Micrel
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-Lead SOP (M)
0.122 (3.10) 0.112 (2.84)
0.199 (5.05) 0.187 (4.74)
DIMENSIONS: INCH (MM)
0.120 (3.05) 0.116 (2.95) 0.036 (0.90) 0.032 (0.81) 0.043 (1.09) 0.038 (0.97) 0.012 (0.30) R
0.007 (0.18) 0.005 (0.13)
0.012 (0.03) 0.0256 (0.65) TYP
0.008 (0.20) 0.004 (0.10)
5 MAX 0 MIN
0.012 (0.03) R 0.039 (0.99) 0.035 (0.89) 0.021 (0.53)
8-Lead MSOP (MM)
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MIC2536
MIC2536
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
MIC2536
12
March 2000

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