Datasheet

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LTC4210-1/LTC4210-2

421012f

APPLICATIO S

DESCRIPTIO

FEATURES

TYPICAL APPLICATIO

The LTC

4210 is a 6-pin SOT-23 Hot Swap

controller

that allows a board to be safely inserted and removed from

a live backplane. An internal high side switch driver

controls the GATE of an external N-channel MOSFET for a

supply voltage ranging from 2.7V to 16.5V. The LTC4210

provides the initial timing cycle and allows the GATE to be

ramped up at an adjustable rate.

The LTC4210 features a fast current limit loop providing

active current limiting together with a circuit breaker

timer. The signal at the ON pin turns the part on and off and

is also used for the reset function.

This part is available in two options: the LTC4210-1 for

automatic retry on overcurrent fault and the LTC4210-2

for latch off on an overcurrent fault.

■

Allows Safe Board Insertion and Removal

from a Live Backplane

■

Adjustable Analog Current Limit

with Circuit Breaker

■

Fast Response Limits Peak Fault Current

■

Automatic Retry or Latch Off On Current Fault

■

Adjustable Supply Voltage Power-Up Rate

■

High Side Drive for External MOSFET Switch

■

Controls Supply Voltages from 2.7V to 16.5V

■

Undervoltage Lockout

■

Adjustable Overvoltage Protection

■

Low Profile (1mm) SOT-23 (ThinSOT

) Package

■

Hot Board Insertion

■

Electronic Circuit Breaker

■

Industrial High Side Switch/Circuit Breaker

Hot Swap Controller in

6-Lead SOT-23 Package

, LTC and LT are registered trademarks of Linear Technology Corporation.

Single Channel 5V Hot Swap Controller

ThinSOT and Hot Swap are trademarks of Linear Technology Corporation.

Power-Up Sequence

SENSE

LTC4210

470µF

LOAD

OUT

GND

4210 TA01

100Ω

GATE

GND

TIMER

SHORT

LONG

GND

LONG

Z1: ISMA10A OR SMAJ10A

ON2

10k

ON1

20k

10Ω

SENSE

0.01Ω

PCB EDGE

CONNECTOR

(MALE)

Si4410DY

OPTIONAL

100Ω

TIMER

0.22µF

0.1µF

0.01µF

BACKPLANE

CONNECTOR

(FEMALE)

4210 TA02

10ms/DIV

OUT

(0.5A/DIV)

OUT

(5V/DIV)

(2V/DIV)

TIMER

(1V/DIV)

LOAD

= 470µF

Summary of content (20 pages)

PAGE 1
LTC4210-1/LTC4210-2 Hot Swap Controller in 6-Lead SOT-23 Package U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®4210 is a 6-pin SOT-23 Hot SwapTM controller that allows a board to be safely inserted and removed from a live backplane. An internal high side switch driver controls the GATE of an external N-channel MOSFET for a supply voltage ranging from 2.7V to 16.5V. The LTC4210 provides the initial timing cycle and allows the GATE to be ramped up at an adjustable rate.
PAGE 2
LTC4210-1/LTC4210-2 W W W AXI U U ABSOLUTE RATI GS U U W PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCC) ............................................... 17V Input Voltage (SENSE, TIMER) .. – 0.3V to (VCC + 0.3V) Input Voltage (ON) ..................................... –0.3V to 17V Output Voltage (GATE) ........ Internally Limited (Note 3) Operating Temperature Range LTC4210-1C/LTC4210-2C ....................... 0°C to 70°C LTC4210-1I/LTC4210-2I ....................
PAGE 3
LTC4210-1/LTC4210-2 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are TA = 25°C. VCC = 5V, unless otherwise noted.
PAGE 4
LTC4210-1/LTC4210-2 U W TYPICAL PERFOR A CE CHARACTERISTICS ∆VGATE vs Supply Voltage ∆VGATE vs Temperature 18 –8.5 16 16 –9.0 14 14 12 12 VCC = 5V VCC = 15V –10.0 –10.5 –11.0 VCC = 12V –11.5 –12.0 –75 –50 –25 0 25 50 18 TA = 25°C ∆VGATE (V) VCC = 3V –9.5 ∆VGATE (V) IGATEUP (µA) IGATEUP vs Temperature –8.
PAGE 5
LTC4210-1/LTC4210-2 U W TYPICAL PERFOR A CE CHARACTERISTICS TIMER High Threshold vs Temperature TIMER High Threshold vs Supply Voltage 1.38 1.38 TA = 25°C 0.24 VCC = 5V 1.36 1.34 1.32 1.30 1.28 1.26 1.34 1.32 1.30 1.28 1.26 1.24 1.24 0 2 4 6 8 10 12 14 16 18 20 SUPPLY VOLTAGE (V) 0 25 50 1.35 0.21 0.20 0.19 0.18 1.45 TA = 25°C VCC = 5V 1.40 HIGH THRESHOLD 1.30 1.25 LOW THRESHOLD 1.20 1.15 0 2 4 LOW THRESHOLD 1.20 1.
PAGE 6
LTC4210-1/LTC4210-2 U W TYPICAL PERFOR A CE CHARACTERISTICS VCB vs Supply Voltage VCB vs Temperature 58 TA = 25°C VCC = 5V 56 56 54 54 52 52 VCB (mV) VCB (mV) 58 50 50 48 48 46 46 44 44 42 0 2 4 6 8 10 12 14 16 18 20 SUPPLY VOLTAGE (V) 4210 G24 42 –75 –50 –25 0 25 50 75 100 125 150 TEMPERATURE (°C) 4210 G25 U U U PI FU CTIO S TIMER (Pin 1): Timer Input Pin. An external capacitor CTIMER sets a 272.9ms/µF initial timing delay and a 21.7ms/ µF circuit breaker delay.
PAGE 7
LTC4210-1/LTC4210-2 W BLOCK DIAGRA 6 5 VCC SENSE + – – INITIAL UP/LATCH OFF UVLO CURRENT LIMIT 0.2V + EA 60µA 5µA 50mV GLITCH FILTER + COMP1 CHARGE PUMP – 1 TIMER LOGIC Z1 12V 10µA + GATE COMP2 1.3V SHUTDOWN M5 – 4 Z2 26V INITIAL DOWN/NORMAL GLITCH FILTER 2µA 2 100µA GND COOL OFF COMP3 – + ON 1.
PAGE 8
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO Hot Circuit Insertion When circuit boards are inserted into live backplanes, the supply bypass capacitors can draw large transient currents from the backplane power bus as they charge. Such transient currents can cause permanent damage to connector pins, glitches on the system supply or reset other boards in the system.
PAGE 9
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO Current Limit Circuit Breaker Function CURRENT FLOW TO LOAD The LTC4210 features a current limiting circuit breaker instead of a traditional comparator circuit breaker. When there is a sudden load current surge, such as a low impedance fault, the bus supply voltage can drop significantly to a point where the power to an adjacent card is affected, causing system malfunctions.
PAGE 10
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO If a 7mΩ sense resistor with ±1% tolerance is used for current limiting, the nominal current limit is 7.14A. From Equations 2 and 3, ILIMIT(MIN) = 6.22A and ILIMIT(MAX) = 8.08A. For proper operation, the minimum current limit must exceed the circuit maximum operating load current with margin. The sense resistor power rating must exceed VCB(MAX)2/RSENSE(MIN).
PAGE 11
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO Whichever method of compensation is used, board level short-circuit testing is highly recommended as board layout can affect transient performance. Beside frequency compensation, the total gate capacitance CGATE also determines the GATE start-up as in Equation 6. The C GATE should be kept below 0.15µF at high supply operation as the capacitive energy ( 0.5 • CGATE • VGATE2 ) is discharged by the LTC4210 internal pull-down transistor.
PAGE 12
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO The current through RSENSE can be divided into two components; ICLOAD due to the total load capacitance (CLOAD) and ILOAD due to the noncapacitive load elements. The capacitive load typically dominates. For a successful start-up without current limit, IRSENSE < ILIMIT: 1 2 3 4 5 >1.
PAGE 13
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO Circuit Breaker Timer Operation A When a current limit fault is encountered at time point A in Figure 5, the circuit breaker timing is activated with a 60µA pull-up. The circuit breaker trips at time point B if the fault is still present and the TIMER pin voltage reaches the COMP2 threshold and the LTC4210 shuts down. For a continuous fault, the circuit breaker delay is: CTIMER 60µA t C TIMER (s / µF ) = 1.
PAGE 14
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO Autoretry After Current Fault (LTC4210-1) Latch-Off After Current Fault (LTC4210-2) Figure 8 shows the waveforms of the LTC4210-1 (autoretry version) during a circuit breaker fault. At time point B1, the TIMER trips the COMP2 threshold of 1.3V. The GATE pin pulls to ground while TIMER begins a “cool-off” cycle with a 2µA pull-down to the COMP1 threshold of 0.2V.
PAGE 15
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO Normal Mode/External Timer Control Whenever the TIMER pin voltage drops below the COMP1 threshold, but is not in reset mode, the TIMER enters normal (100µA source) mode with an equivalent 7k resistive pull-down. Table 1 shows the relationship of tINITIAL, tCBDELAY, tCOOLOFF vs CTIMER. If the TIMER pin is pulled beyond the COMP2 threshold, the GATE pin is pulled to ground immediately.
PAGE 16
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO RSENSE VCC RSENSE Q1 VOUT D1* VCC D1* *USER SELECTED VOLTAGE CLAMP (A LOW BIAS CURRENT ZENER DIODE IS RECOMMENDED) 1N4688 (5V) 1N4692 (7V) 1N4695 (9V) 1N4702 (15V) RS 200Ω GATE (10a) Q1 VOUT D2* RS 200Ω GATE (10b) Figure 10. Gate Protection Zener Clamp BACKPLANE PCB EDGE CONNECTOR CONNECTOR (FEMALE) (MALE) VIN 5V RSENSE 0.01Ω LONG Z1 SHORT RX Z2 10Ω CX 0.
PAGE 17
LTC4210-1/LTC4210-2 U W U U APPLICATIO S I FOR ATIO A MOSFET with a VGS absolute maximum rating of ±20V meets the two criteria for all the LTC4210 applications ranges from 2.7V to 16.5V. Typically most 10V gate rated MOSFETs have VGS absolute maximum ratings of ±20V or greater, so no external VGS Zener clamp is needed. There are 4.5V gate rated MOSFETs with VGS absolute maximum ratings of ±20V.
PAGE 18
LTC4210-1/LTC4210-2 U APPE DIX Table 2 lists some current sense resistors that can be used with the circuit breaker. Table 3 lists some power MOSFETs that are available. Table 4 lists the web sites of several manufacturers. Since this information is subject to change, please verify the part numbers with the manufacturer. Table 2. Sense Resistor Selection Guide CURRENT LIMIT VALUE PART NUMBER DESCRIPTION MANUFACTURER 1A LR120601R050 0.05Ω 0.5W 1% Resistor IRC-TT 2A LR120601R025 0.025Ω 0.
PAGE 19
LTC4210-1/LTC4210-2 U PACKAGE DESCRIPTIO S6 Package 6-Lead Plastic TSOT-23 (Reference LTC DWG # 05-08-1636) 0.62 MAX 2.90 BSC (NOTE 4) 0.95 REF 1.22 REF 3.85 MAX 2.62 REF 1.4 MIN 2.80 BSC 1.50 – 1.75 (NOTE 4) PIN ONE ID RECOMMENDED SOLDER PAD LAYOUT PER IPC CALCULATOR 0.30 – 0.45 6 PLCS (NOTE 3) 0.95 BSC 0.80 – 0.90 0.20 BSC 0.01 – 0.10 1.00 MAX DATUM ‘A’ 0.30 – 0.50 REF 0.09 – 0.20 (NOTE 3) 1.90 BSC S6 TSOT-23 0302 NOTE: 1. DIMENSIONS ARE IN MILLIMETERS 2. DRAWING NOT TO SCALE 3.
PAGE 20
LTC4210-1/LTC4210-2 U TYPICAL APPLICATIO 12V Hot Swap Application BACKPLANE PCB EDGE CONNECTOR CONNECTOR (MALE) (FEMALE) RSENSE 0.01Ω LONG VIN 12V Z1 + RX 10Ω CX 0.1µF 6 VCC SHORT RON1 62k 3 RON2 10k Q1 Si4410DY 1 ON 5 SENSE GATE LTC4210 TIMER 4 VOUT 12V 4A CLOAD 470µF RG 200Ω RC 100Ω CC 10nF GND LONG GND CTIMER 0.