LTC4216 Ultralow Voltage Hot Swap Controller Features n n n n n n n n n n n n Description Allows Safe Board Insertion and Removal from a Live Backplane Controls Load Voltages from 0V to 6V Fast Response Limits Peak Fault Current Adjustable Analog Current Limit Adjustable Soft-Start with Inrush Current Limiting Adjustable Response Time for Overcurrent Protection Low Circuit Breaker Trip Threshold: 25mV No External Gate Capacitor Required Internal Charge Pump for N-Channel MOSFET Adjustable Output Power-U
LTC4216 Absolute Maximum Ratings (Note 1) Bias Supply Voltage (VCC).............................– 0.3V to 9V Input Voltages FB, ON, SS, SENSEP, SENSEN..................– 0.3V to 9V TIMER, FILTER..............................–0.3V to VCC + 0.3V Output Voltages RESET, FAULT........................................... –0.3V to 9V GATE....................................................... –0.3V to 15V Operating Temperature Range LTC4216C................................................. 0°C to 70°C LTC4216I...
LTC4216 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted. (Note 2) SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS ΔVCB(TH) Circuit Breaker Trip Voltage Threshold (VSENSEP – VSENSEN) VSENSEP = 0.4V, 3.3V l 22.5 21.5 25 25 27.5 28.
LTC4216 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCC = 3.3V, unless otherwise noted.
LTC4216 Typical Performance Characteristics VGATE vs VSENSEN ΔVGATE vs Temperature VSENSEP = VSENSEN = VCC IGATE(UP) vs Temperature –22 VCC = 6V 12 –21 VCC = 5V 10 VCC = 3.3V 6.0 5.5 IGATE(UP) (µA) 6.5 ∆VGATE (V) 14 VGATE (V) 7.0 8 6 VCC = 2.5V –19 5.0 4 4.5 –50 –25 25 75 0 50 TEMPERATURE (°C) 100 2 125 0 1 2 3 4 –18 –50 6 –25 25 75 0 50 TEMPERATURE (°C) 4216 G08 VFB(TH) vs Temperature 100 125 4216 G09 VTMR(TH) vs Temperature 0.611 VON(TH) vs Temperature 1.27 0.
LTC4216 Typical Performance Characteristics –70 IFILT(UP) vs Temperature IFILT(DN) vs Temperature –12 2.8 ISS(UP) vs Temperature VFB = 2V –10 2.6 –60 –55 –8 ISS(UP) (µA) IFILT(DN) (µA) IFILT(UP) (µA) –65 2.4 –6 –4 2.2 –2 –50 –50 –25 25 75 0 50 TEMPERATURE (°C) 100 125 2.
LTC4216 Pin Functions (DE12/Package/MS Package) resistor is placed in the power path between SENSEP and SENSEN pins to sense the output current. The electronic circuit breaker trips if the voltage across the sense resistor exceeds 25mV for more than a fault filter delay. SENSEP (Pin 10/Pin 9): Circuit Breaker Positive Sense Input. Connect this pin to the sense resistor terminal wired to the positive supply input for the external output load. This positive supply range extends from 0V to 6V.
LTC4216 Block Diagram VCC SENSEP 2.12V VCC 2µA 0.2V 25mV – + SENSEN – + – + UVLO ECB 6µs DELAY FILTER DELAY (SEE NOTE 1) + 40mV OUT OF UVLO GATE D1 – + – + VCC VCC 20µA 10µA M1 ACL M3 M4 CB TRIPS OR UVLO FAULT LATCH-OFF CP4 – TIMER CHARGE PUMP Z1 M2 100µA GATE OFF GATE ON 1µA M5 SS** M6 R1 GATE OFF RESET + M9 LOGIC 1.253V VCC NORMAL + DEVICE RESET GATE ON FAULT LATCH RESET 30µs DELAY + FILTER FUNCTION OF OVERDRIVE 3µs DELAY 2.4µA CB TRIPS 1.
LTC4216 Applications Information Hot Circuit Insertion When circuit boards are inserted into a live backplane, the supply bypass capacitors can draw huge transient current from the power bus as they charge. Potentially, the flow of current could damage the connector pins and glitch the power bus, causing other boards in the system to reset. The LTC4216 is designed to turn on or off a circuit board supply in a controlled manner, allowing insertion or removal without glitches or connector damage.
LTC4216 Applications Information 1.253V • C1 2µA (1) For example, if C1 = 10nF, tTIMER = 6.2ms. FB Glitch Filtering The FB pin is used to monitor the output voltage of the external MOSFET through a resistive divider. Any transients on the FB pin due to the output low spikes will pull RESET low. To prevent RESET from generating an unwanted system reset, the FB comparator has a glitch filter to ride out these glitches.
LTC4216 Applications Information Electronic Circuit Breaker The LTC4216 features an electronic circuit breaker function that protects the external MOSFET against short-circuits or excessive load current conditions on the supply. An external sense resistor connected between SENSEP and SENSEN pins is used to measure the load current.
LTC4216 Applications Information NORMALIZED RESPONSE TIME (s/µF) 1 t/C3(s/µF) = 1.253/[(60 • D) – 2.4] 0.1 0.01 0 20 40 60 80 OVERLOAD DUTY CYCLE, D (%) 100 4216 F06 Figure 6. Circuit Breaker Filter Response for Intermittent Overload Analog Current Limiting In addition to an electronic circuit breaker, the LTC4216 has included a novel analog current limit (ACL) amplifier that does not require an external compensation capacitor at the GATE pin.
LTC4216 Applications Information For example, if C 2 = 10nF, dVSS(SLOW) = 0.1V /ms. dt dVSS(NOM) = 1V /ms and dt After the initial timing cycle, the SS capacitor is charged by a 10µA current source pull-up and GATE is held low by the ACL amplifier. As SS ramps up, the ACL amplifier releases the GATE when it crosses its input offset voltage. At this instant, SS switches the pull-up current from 10µA to 1µA for a slower ramp rate.
LTC4216 Applications Information Normal Power-Up and Power-Down Figure 8 illustrates the timing diagram for a normal powerup sequence in the case where a printed circuit board is inserted into a live backplane. At time point 1, the bias supply (VCC) ramps up and enables the device when the supply voltage rises above the undervoltage lockout threshold (2.12V). At time point 2, SENSEP supply, together with the ON pin, ramp up and start the first timing cycle when the ON pin voltage exceeds 0.8V.
LTC4216 Applications Information capacitors. A second timing cycle starts at time point 11 when the FB pin voltage exceeds 0.6V and the voltage across the sense resistor drops below 25mV.RESET goes ELECTRONIC CIRCUIT BREAKER ARMED CHECK FOR GATE, FILTER, TIMER, SS < 0.2V 12 high at the end of the second timing cycle (time point 12) when TIMER reaches the VTMR(TH) threshold. ON GOES LOW CHECK FOR GATE, FILTER, TIMER, SS < 0.2V AND FAULT HIGH START 2ND TIMING CYCLE START (CHECK TIMER < 0.
LTC4216 Applications Information FILTER RAMPS UP WHEN (VSENSEP – VSENSEN) > 25mV OUTPUT IN ANALOG CURRENT LIMIT, (VSENSEP – VSENSEN) = 40mV CHECK FOR GATE, FILTER, TIMER, SS < 0.2V AND FAULT HIGH ELECTRONIC CIRCUIT BREAKER ARMED CHECK FOR GATE, FILTER, TIMER, SS < 0.2V OUTPUT NO LONGER IN CURRENT LIMIT 12 3 RESET PULLED LOW DUE TO POWER BAD 2ND TIMING CYCLE CANNOT START WITH OUTPUT IN ANALOG CURRENT LIMIT 4 5 6 7 8 RESET GOES HIGH 9 10 11 ON GOES LOW (ON < 0.72V) 12 IN RESET MODE (ON < 0.
LTC4216 Applications Information Power-Up into an Output-Short Sense Resistor Considerations Figure 10 shows the timing diagram in the case when the output is a dead short during power-up. As GATE ramps up at time point 6, the MOSFET current increases due to the output short causing the voltage drop across the sense resistor to rise above 25mV. FILTER sources 60µA, charging the external capacitor. At time point 7, GATE regulates to limit the output current to 40mV/RSENSE.
LTC4216 Applications Information For example, if ILOAD(MAX) = 5A, RSENSE = 4.3mΩ. The nearest standard value is 4mΩ. For proper circuit breaker operation, kelvin-sense PCB connections between the sense resistor and the LTC4216’s SENSEP and SENSEN pins are strongly recommended. Figure 12 illustrates the correct way of making connections between the LTC4216 and the sense resistor. PCB layout should be balanced and symmetrical to minimize wiring errors.
LTC4216 Applications Information 1. Maximum drain-to-source voltage, VDS(MAX) The VDS(MAX) rating must exceed the maximum load supply voltage including spikes and ringing. 2. Gate-to-source voltage, VGS, overdrive The absolute maximum rating for VGS is typically ±8V for “logic level” and “sub-logic level” MOSFETs. 3. Drain-to-source resistance, RDS(ON) The RDS(ON) should be low for low voltage applications to allow its drain-to-source voltage, VDS(ON), to be a very small percentage of the supply voltage.
LTC4216 Applications Information the plug-in boards, the LTC4216 provides two separate pins for bias supply input and load supply sensing. With this configuration, an RC network, RY and CY, shown in Figure 13, can be used with the VCC pin to ride out supply glitches during output short or adjacent board short.
LTC4216 Applications Information An example with LTC4216 mounted on the backplane is shown in Figure 15. In this case, the NPN transistor, Q1, and two resistors, R7 and R8, form the PCB connection sensing circuit with the ON pin. With the PCB out of the backplane connector, Q1 base is tied to load supply through R7, turning Q1 on and pulling the LTC4216’s ON pin low. The base of Q1 is also wired to the backplane connector pin.
LTC4216 Applications Information BACKPLANE PCB EDGE CONNECTOR CONNECTOR (FEMALE) (MALE) LONG VCC 5V CY 330nF RY 22Ω RSENSE 0.004Ω LONG VIN 3.3V SHORT R3 20k 1% ON/OFF LONG GND 11 10 9 8 VCC SENSEP SENSEN GATE ON R2 M2 4.42k 1% FB 7 R4 10k 1% LTC4216 FAULT R1 M3 5.62k 1% SHORT + R5 39.2k 1% 2 SHORT ON/RST CX RX 100nF 10Ω R8 10k Z1 M1 Si4864DY 4 PCB CONNECTION SENSING 5 C1 10nF GND RESET FILTER SS TIMER C2 4.
LTC4216 Applications Information capacitor, C2, from 0V to its final value (1.65V) by 10µA current source only. FAULT VOL to VON(TH) threshold (0.8V). As there is an internal 5µA current source pull-up at the FAULT pin, it complicates the equation for tOFF. This is approximately given by: tOFF ≈ RAUTO • C AUTO •(VON(TH) − VOL ) (VIN – VON(TH) ) + RAUTO • 5µA For the component values shown, the external RC time constant is set at 0.2 second, tTIMER = 62ms, tOFF = 25ms at VIN = 5V, tSS = 1.
LTC4216 Package Description Please refer to http://www.linear.com/designtools/packaging/ for the most recent package drawings. DE/UE Package 12-Lead Plastic DFN (4mm × 3mm) (Reference LTC DWG # 05-08-1695 Rev D) NOTE: 1. DRAWING PROPOSED TO BE A VARIATION OF VERSION (WGED) IN JEDEC PACKAGE OUTLINE M0-229 2. DRAWING NOT TO SCALE 3. ALL DIMENSIONS ARE IN MILLIMETERS 4. DIMENSIONS OF EXPOSED PAD ON BOTTOM OF PACKAGE DO NOT INCLUDE MOLD FLASH. MOLD FLASH, IF PRESENT, SHALL NOT EXCEED 0.15mm ON ANY SIDE 5.
LTC4216 Revision History REV DATE DESCRIPTION A 4/13 Corrected Supply Voltage to Output in the tenth feature PAGE NUMBER 1 Raised DE storage temperature limit to 150°C. Separated Order Information as per latest format 2 Condition specified for ΔVCB(TH). New specification for tCB(TRIP) without FILTER capacitor. 3 Added new curve: Analog Current Limit Delay vs Sense Voltage 4 Removed curve: VFAULT(TH) vs Temperature 5 Updated RESET pin description.
LTC4216 Typical Application LTC4216CMS with Gate Capacitor for Slew Rate Control VIN 5V BACKPLANE PCB EDGE CONNECTOR CONNECTOR (FEMALE) (MALE) LONG Z1 RSENSE 0.01Ω RX 10Ω CX 100nF SHORT CY 330nF RG 10Ω RY 22Ω VCC SENSEP SENSEN GATE SHORT RESET R5 10k RESET C4 22nF FB LTC4216 R2 10k R4 64.9k 1% + VOUT 5V CLOAD 2A 470µF R3 10k 1% ON FILTER TIMER LONG GND M1 Si9426DY C1 10nF GND C3 68nF Z1: SMAJ6.
