Datasheet

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LTC4217

4217fe

Typical applicaTion

FeaTures

applicaTions

DescripTion

2A Integrated Hot Swap

Controller

The LTC

4217 is an integrated solution for Hot Swap™

applications that allows a board to be safely inserted and

removed from a live backplane. The part integrates a Hot

Swap controller, power MOSFET and current sense resistor

in a single package for small form factor applications. A

dedicated 12V version (LTC4217-12) contains preset 12V

specific thresholds, while the standard LTC4217 allows

adjustable thresholds.

The LTC4217 provides separate inrush current control

and a 5% accurate 2A current limit with foldback cur-

rent limiting. The current limit threshold can be adjusted

dynamically using an external pin. Additional features

include a current monitor output that amplifies the sense

resistor voltage for ground referenced current sensing

and a MOSFET temperature monitor output. Thermal limit,

overvoltage, undervoltage and power good monitoring

are also provided.

L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear

Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation.

All other trademarks are the property of their respective owners.

12V, 1.5A Card Resident Application

Small Footprint

33mΩ MOSFET with R

SENSE

Wide Operating Voltage Range: 2.9V to 26.5V

Adjustable, 5% Accurate Current Limit

Current and Temperature Monitor Outputs

Overtemperature Protection

Adjustable Current Limit Timer Before Fault

Power Good and Fault Outputs

Adjustable Inrush Current Control

2% Accurate Undervoltage and Overvoltage

Protection

Available in 20-Lead TSSOP and 16-Lead

5mm × 3mm DFN Packages

RAID Systems

Server I/O Cards

Industrial

Power-Up Waveforms

ADC

0.1µF

12V

OUT

12V

1.5A

20k

4217 TA01a

10k

12V

330µF

OUT

SET

GND

MON

LTC4217DHC-12

INTV

TIMER

F LT

AUTO

RETRY

10V/DIV

0.1A/DIV

OUT

10V/DIV

25ms/DIV

4217 TA01b

Summary of content (18 pages)

PAGE 1
LTC4217 2A Integrated Hot Swap Controller Features n n n n n n n n n n n Description Small Footprint 33mΩ MOSFET with RSENSE Wide Operating Voltage Range: 2.9V to 26.
PAGE 2
LTC4217 Absolute Maximum Ratings (Notes 1, 2) Supply Voltage (VDD).................................. –0.3V to 28V Input Voltages FB, OV, UV............................................... –0.3V to 12V TIMER.................................................... –0.3V to 3.5V SENSE..............................VDD – 10V or – 0.3V to VDD Output Voltages ISET, IMON.................................................. –0.3V to 3V PG, FLT................................................... –0.3V to 35V OUT.............
PAGE 3
LTC4217 Order Information LEAD FREE FINISH TAPE AND REEL PART MARKING* LTC4217CDHC-12#PBF LTC4217CDHC-12#TRPBF 421712 PACKAGE DESCRIPTION TEMPERATURE RANGE 16-Lead (5mm × 3mm) Plastic DFN 0°C to 70°C LTC4217IDHC-12#PBF LTC4217IDHC-12#TRPBF 421712 16-Lead (5mm × 3mm) Plastic DFN –40°C to 85°C LTC4217CDHC#PBF LTC4217CDHC#TRPBF 16-Lead (5mm × 3mm) Plastic DFN 0°C to 70°C 4217 LTC4217IDHC#PBF LTC4217IDHC#TRPBF 4217 16-Lead (5mm × 3mm) Plastic DFN –40°C to 85°C LTC4217CFE#PBF LTC4217CFE#T
PAGE 4
LTC4217 Electrical Characteristics The l denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VDD = 12V unless otherwise noted. SYMBOL PARAMETER CONDITIONS MIN IIN OV, UV, FB Pin Input Current VIN = 1.2V, LTC4217 l TYP MAX UNITS 0 ±1 µA kΩ Inputs RIN OV, UV, FB Pin Input Resistance LTC4217-12 l 13 18 23 VTH OV, UV, FB Pin Threshold Voltage VIN Rising l 1.21 1.235 1.
PAGE 5
LTC4217 Typical Performance Characteristics IDD vs VDD 3.5 INTVCC (V) 1.6 25°C 1.4 –40°C VDD = 3.3V 2.0 1.5 1.0 1.2 0 5 10 15 VDD (V) 20 25 0 30 0 –2 –4 4217 G01 1.230 1.228 –6 –8 ILOAD (mA) –10 –12 –14 0.06 –25 0 25 50 TEMPERATURE (°C) 75 –100 –95 –90 –50 –25 50 0 25 TEMPERATURE (°C) 75 4217 G04 2.5 1.5 1.0 0.5 0 0.2 0.4 0.6 0.8 FB VOLTAGE (V) 1.0 1.2 4217 G07 100 100 10 1 0.
PAGE 6
LTC4217 Typical Performance Characteristics RON vs VDD and Temperature TA = 25°C, VDD = 12V unless otherwise noted. PG, FLT VOUT Low vs ILOAD MOSFET SOA Curve 60 14 10 12 VDD = 3.3V, 12V, 24V 1 1ms ID (A) RON (mΩ) 40 30 20 10ms 100ms 0.1 10 0 –50 –25 0 25 50 TEMPERATURE (°C) 75 0.01 100 TA = 25°C MULTIPLE PULSE DUTY CYCLE = 0.2 0.1 1 IGATE PULL-UP (µA) 95 90 85 –25 0 25 50 TEMPERATURE (°C) 75 –25.0 –24.
PAGE 7
LTC4217 Pin Functions FB: Foldback and Power Good Input. Connect this pin to an external resistive divider from OUT for the LTC4217 (adjustable) version. The LTC4217-12 version uses a fixed internal divider with optional external adjustment. Open the pin if the LTC4217-12 thresholds for 12V operation are desired. If the voltage falls below 0.6V, the current limit is reduced using a foldback profile (see the Typical Performance Characteristics section). If the voltage falls below 1.
PAGE 8
LTC4217 Functional Diagram SENSE (EXPOSED PAD) INTERNAL 7.5mΩ SENSE RESISTOR VDD GATE INTERNAL 25mΩ MOSFET OUT IMON CLAMP – +– ISET CHARGE PUMP AND GATE DRIVER CS + INRUSH 0.6V POSITIVE TEMPERATURE COEFFICIENT REFERENCE 0.3V/ms 20k X1 OUT FB CM FOLDBACK 0.6V + UV * – UV 20k * 20k * PG – 140k 1.235V 150k + VDD OUT LOGIC 1.235V PG * 0.62V + RST – VDD 224k 0.2V * INTVCC – + * FLT TM1 OV 20k + 100µA OV 1.235V – 2µA + VDD TM2 VDD – 1.235V – 3.
PAGE 9
LTC4217 Operation The Functional Diagram displays the main circuits of the device. The LTC4217 is designed to turn a board’s supply voltage on and off in a controlled manner allowing the board to be safely inserted and removed from a live backplane. The LTC4217 includes a 25mΩ MOSFET and a 7.5mΩ current sense resistor. During normal operation, the charge pump and gate driver turn on the pass MOSFET’s gate to provide power to the load. The inrush current control is accomplished by the INRUSH circuit.
PAGE 10
LTC4217 Applications Information FB UV R1 224k GATE RGATE 1k FLT R4 20k R2 20k R5 150k LTC4217FE R3 140k VOUT 12V 0.8A OUT VDD 12V OV + CL 330µF R6 20k CGATE 0.1µF 12V R7 10k PG ISET RSET 20k evident from this graph that the power dissipation at 12V, 300mA for 40ms is in the safe region. Adding a capacitor and a 1k series resistor from GATE to ground will lower the inrush current below the default value set by the INRUSH circuit.
PAGE 11
LTC4217 Applications Information LTC4217 GATE CP 2.2nF *OPTIONAL RC TO LOWER INRUSH CURRENT 4217 F03 Figure 3. Compensation for Small CLOAD over temperature. Normally the switch is turned off with a 250µA current pulling down the GATE pin to ground. With the switch turned off, the OUT voltage drops which pulls the FB pin below its threshold. PG then pulls low to indicate output power is no longer good. If VDD drops below 2.65V for greater than 5µs or INTVCC drops below 2.
PAGE 12
LTC4217 Applications Information a resistor between the ISET pin and ground. As shown in the Functional Diagram the voltage at the ISET pin (via the clamp circuit) sets the CS amplifier’s built-in offset voltage. This offset voltage directly determines the active current limit value. With the ISET pin open, the voltage at the ISET pin is determined by a positive temperature coefficient reference. This voltage is set to 0.618V at room temperature which corresponds to a 2A current limit at room temperature.
PAGE 13
LTC4217 Applications Information 12V Fixed Version In the LTC4217-12 the UV, OV and FB pins are driven by internal dividers which may need to be filtered to prevent false faults. By placing a bypass capacitor on these pins the faults are delayed by the RC time constant. Use the RIN value from the electrical characteristics table for this calculation. In cases where the fixed thresholds need a slight adjustment, placing a resistor from the UV or OV pins to VDD or GND will adjust the threshold up or down.
PAGE 14
LTC4217 Applications Information invoked by tying the TIMER pin to INTVCC. After the 2ms timeout the FLT pin needs to pull-down on the UV pin to restart the power-up sequence. Since the default values for overvoltage, undervoltage and power good thresholds for the 12V fixed version match the requirements, no external components are required for the UV, OV and FB pins. The final schematic in Figure 6 results in very few external components.
PAGE 15
LTC4217 Package Description DHC Package 16-Lead Plastic DFN (5mm × 3mm) (Reference LTC DWG # 05-08-1706) 0.65 ±0.05 3.50 ±0.05 1.65 ±0.05 2.20 ±0.05 (2 SIDES) PACKAGE OUTLINE 0.25 ± 0.05 0.50 BSC 4.40 ±0.05 (2 SIDES) RECOMMENDED SOLDER PAD PITCH AND DIMENSIONS 5.00 ±0.10 (2 SIDES) R = 0.20 TYP 3.00 ±0.10 (2 SIDES) 9 R = 0.115 TYP 0.40 ± 0.10 16 1.65 ± 0.10 (2 SIDES) PIN 1 TOP MARK (SEE NOTE 6) PIN 1 NOTCH 0.200 REF 0.75 ±0.05 0.00 – 0.05 8 1 0.25 ± 0.05 0.50 BSC (DHC16) DFN 1103 4.40 ±0.
PAGE 16
LTC4217 Package Description FE Package 20-Lead Plastic TSSOP (4.4mm) (Reference LTC DWG # 05-08-1663) Exposed Pad Variation CA 6.40 – 6.60* (.252 – .260) 4.95 (.195) 4.95 (.195) 20 1918 17 16 15 14 13 12 11 6.60 ±0.10 4.50 ±0.10 2.74 (.108) 6.40 2.74 (.252) (.108) BSC SEE NOTE 4 0.45 ±0.05 1.05 ±0.10 0.65 BSC 1 2 3 4 5 6 7 8 9 10 RECOMMENDED SOLDER PAD LAYOUT 4.30 – 4.50* (.169 – .177) 0.09 – 0.20 (.0035 – .0079) 0.25 REF 0.50 – 0.75 (.020 – .030) NOTE: 1.
PAGE 17
LTC4217 Revision History (Revision history begins at Rev C) REV DATE DESCRIPTION C 12/09 Revise Features, Description and Typical Application PAGE NUMBER Revise Absolute Maximum Ratings Storage Temperature Range and Pin Configuration Revise Electrical Characteristics 1 2 3, 4 Revise Graph G11 6 Update Pin Functions 7 Update Functional Diagram 8 Update Operation Section Revise Figure 1 and Update Values and Equation in Applications Information Section D 1/11 Added H-grade to Absolute Maxim
PAGE 18
LTC4217 Typical Application 24V, 1.5A Card Resident Application OUT VDD 24V 158k LTC4217FE * 200k FB UV 24V FLT 3.24k + OV VOUT 24V 100µF 1.5A 10k 10k 10k PG TIMER INTVCC 0.1µF GND IMON ADC 20k 4217 TA02 *DIODES INC. SMAJ24A Related Parts PART NUMBER DESCRIPTION COMMENTS LTC1421 Dual Channel, Hot Swap Controller Operates from 3V to 12V, Supports –12V, SSOP-24 LTC1422 Single Channel, Hot Swap Controller Operates from 2.