Datasheet

ManualsBrandsMAXIM INTEGRATED ManualsPMICsPMIC - hot swap controller Multi-purpose SOIC 8 Surface-mount

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General Description

The MAX4370 is a circuit-breaker IC designed to offer

protection in hot-swap applications using Maxim’s

DualSpeed/BiLevel™ detection. This controller,

designed to reside either on the backplane or on the

removable card, is used to protect a system from start-

up damage when a card or board is inserted into a rack

with the main system power supply turned on. The

card’s discharged filter capacitors provide a low

impedance that can momentarily cause the main power

supply to collapse. The MAX4370 prevents this start-up

condition by providing inrush current regulation during

a programmable start-up period, allowing the system to

stabilize safely. In addition, two on-chip comparators

provide DualSpeed/BiLevel short-circuit protection and

overcurrent protection during normal operation.

The MAX4370 provides protection for a +3V to +12V

single supply. An internal charge pump generates the

controlled gate drive for an external N-channel MOS -

FET power switch. The MAX4370 latches the switch off

after a fault condition until an external reset signal

clears the device. Other features include a status pin to

indicate a fault condition, an adjustable overcurrent

response time, and a power-on reset comparator.

The MAX4370 is specified for the extended-industrial

temperature range (-40°C to +85°C) and is available in

an 8-pin SO package.

Applications

Hot Board Insertion

Solid-State Circuit Breaker

Features

♦ DualSpeed/BiLevel Protection During Normal

Operation

♦ Inrush Current Regulated at Start-Up

♦ Resides Either on the Backplane or on the

Removable Card

♦ Programmable Start-Up Period and Response

Time

♦ Allows Safe Board Insertion and Removal from

Live Backplane

♦ Protection for +3V to +12V Single Supplies

♦ Latched Off After Fault Condition

♦ Status Output Pin

♦ Internal Charge Pump Generates Gate Drive for

External N-Channel MOSFET

MAX4370

†

Current-Regulating Hot-Swap Controller with

DualSpeed/BiLevel Fault Protection

________________________________________________________________

Maxim Integrated Products

MAX4370

OUT

BOARD

CTIM

TIM

CSPD

SPD

GND

STAT

SENSE

STAT

REMOVABLE CARDBACKPLANE

VSEN GATE

GND

Typical Operating Circuit

19-1472; Rev 0; 4/99

PART

MAX4370ESA -40°C to +85°C

TEMP. RANGE PIN-PACKAGE

8 SO

Ordering Information

DualSpeed/BiLevel is a trademark of Maxim Integrated Products.

†

Pin Configuration appears at end of data sheet.

Summary of content (16 pages)

PAGE 1
9-1472; Rev 0; 4/99 Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection Features The MAX4370 is a circuit-breaker IC designed to offer protection in hot-swap applications using Maxim’s DualSpeed/BiLevel™ detection. This controller, designed to reside either on the backplane or on the removable card, is used to protect a system from startup damage when a card or board is inserted into a rack with the main system power supply turned on.
PAGE 2
MAX4370 Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection ABSOLUTE MAXIMUM RATINGS VIN to GND...........................................................................+15V STAT to GND ..........................................................-0.3V to +14V GATE to GND ..............................................-0.3V to (VIN + 8.5V) ON to GND (Note 1) ................................................. -1V to +14V CSPD to GND .............-0.3V to the lower of (VIN + 0.
PAGE 3
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection MAX4370 ELECTRICAL CHARACTERISTICS (continued) (VIN = +2.7V to +13.2V, TA = -40°C to +85°C, unless otherwise noted. Typical values are at VIN = +5V and TA = +25°C.) (Note 2) PARAMETER SYMBOL CONDITIONS MIN TYP MAX 0.575 0.6 0.
PAGE 4
Typical Operating Characteristics (Circuit of Figure 7, V IN = 5V, R SENSE = 100mΩ, M1 = FDS6670A, C BOARD = 470µF, C GATE = 0, R S = 0, T A = +25°C, unless otherwise noted.) 0.8 0.5 0.4 ON = GND 0.7 50.8 50.4 0.6 0.5 0.4 VIN = 3V 0.3 50.0 49.8 0.2 49.4 0.1 49.2 2 4 6 8 10 12 49.0 0 -40 14 -15 10 SLOW COMPARATOR RESPONSE TIME vs.
PAGE 5
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection GATE CHARGE CURRENT vs. TEMPERATURE 100 IGATE = 10µA 20 TA = +85°C IGATE (µA) VIN = 5.0V VIN = 3.0V 60 VGATE (V) 100 80 IGATE (µA) VGATE = 0 VIN = 12V 125 25 MAX4370 toc11 VIN = 12V GATE VOLTAGE vs. INPUT VOLTAGE 150 MAX4370 toc10 120 VIN = 5V 75 TA = +25°C 15 TA = -40°C 10 40 50 20 25 MAX4370 toc12 GATE CHARGE CURRENT vs.
PAGE 6
Typical Operating Characteristics (continued) (Circuit of Figure 7, V IN = 5V, R SENSE = 100mΩ, M1 = FDS6670A, C BOARD = 470µF, C GATE = 0, R S = 0, T A = +25°C, unless otherwise noted.) MAX4370-20 VGATE ILOAD (1A/div) (2V/div) 0V 0V VIN = 5V 0.1 VIN = 3V 0.1 1 10 100 0.1 RISING 0.601 FALLING 0.599 0.597 0 2 4 6 8 10 12 0.6075 VIN = 5V 0.6025 } } 0.6000 VIN = 3V 0.5975 -40 -15 10 35 TEMPERATURE (°C) UVLO DELAY vs.
PAGE 7
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection PIN NAME FUNCTION 1 VIN 2 VSEN Current-Sense Resistor Voltage Input. RSENSE is connected from VIN to VSEN. 3 GATE Gate Drive Output. Connect to gate of external N-channel MOSFET. 4 GND Ground 5 CSPD Slow Comparator Speed Setting. Leave floating or connect the timing capacitor from CSPD to GND. See Slow Comparator Response Time section. 6 CTIM Start-Up Timer Setting.
PAGE 8
MAX4370 Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection Detailed Description The MAX4370 is a circuit-breaker IC designed for hotswap applications where a card or board is to be inserted into a rack with the main system power supply turned on. Normally, when a card is plugged into a live backplane, the card is discharged filter capacitors provide a low impedance, which can momentarily cause the main power supply to collapse.
PAGE 9
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection VGATE ~VIN Fast Comparator VOUT ~VTH td ILIM ILOAD tOFF Figure 3. Response to a Fault Condition Slow Comparator The slow comparator is disabled at start-up while the external MOSFET is turning on. This allows the part to ignore the higher-than-normal inrush current charging the board capacitors (C BOARD) when a card is first plugged in.
PAGE 10
MAX4370 Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection Status Output The status output is an open-drain output that goes low when the part is: 1) in start-up 2) forced off (on = GND) 3) in an overcurrent condition, or ON VIN OV 1.2V CTIM 4) latched off. STAT is high only if the part is in normal mode and no faults are present (Table 1). Figure 4 shows the STAT timing diagram.
PAGE 11
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection N-Channel MOSFET Select the external N-channel MOSFET according to the application’s current level. The MOSFET’s R DS(ON) should be chosen low enough to have a minimum volt age drop at full load to limit the MOSFET power dissipation. High R DS(ON) can cause output ripple if the board has pulsing loads, or it can trigger an external undervoltage reset monitor at full load.
PAGE 12
MAX4370 Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection Case A: Slow Turn-On (without overcurrent) There are two ways to turn on the MOSFET without reaching the fast comparator current limit: 1) If the board capacitance (C BOARD ) is low, the inrush current is low. 2) If the capacitance at GATE is high, the MOSFET turns on slowly.
PAGE 13
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection RESPONSE TIME (ms) 100 MAX4370 VREF 1000 tCSPD (ms) = 0.2 · CSPD (nF) R1 ON 10 LOGIC CONTROL 1 NTC R2 0.6V 0.1 0.01 0.01 0.1 1 10 100 R1 = R2 · (VREF / O.6 - 1) R2 = VALUE OF THE NTC RESISTOR AT THE LIMIT TEMPERATURE VREF = ANY REFERENCE VOLTAGE AVAILABLE OR VIN 1000 CSPD (nF) Figure 8. Slow Comparator Response Time vs. CSPD Figure 9.
PAGE 14
MAX4370 Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection Using the MAX4370 on the Backplane The MAX4370 can be used on the backplane to regulate current upon insertion of a removable card. This allows multiple cards with different input capacitance to be inserted into the same slot even if the card doesn’t have on-board hot-swap protection. The MAX4370 current-limiting feature is active during the start-up period set by CTIM.
PAGE 15
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection MAX4370 HIGH-CURRENT PATH SENSE RESISTOR MAX4370 Figure 12.
PAGE 16
Current-Regulating Hot-Swap Controller with DualSpeed/BiLevel Fault Protection SOICN.EPS MAX4370 Package Information Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circu implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.