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LTC1421/LTC1421-2.5

Hot Swap Controller

■

Allows Safe Board Insertion and Removal from a

Live Backplane

■

System Reset and Power Good Control Outputs

■

Programmable Electronic Circuit Breaker

■

User Programmable Supply Voltage Power-Up Rate

■

High Side Driver for Two External N-Channels

■

Controls Supply Voltages from 3V to 12V

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Connection Inputs Detect Board Insertion or Removal

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Undervoltage Lockout

■

Power-On Reset Input

■

Hot Board Insertion

■

Electronic Circuit Breaker

The LTC

1421/LTC1421-2.5 are Hot Swap

controllers

that allow a board to be safely inserted and removed from a

live backplane. Using external N-channel pass transistors,

the board supply voltages can be ramped up at a program-

mable rate. Two high side switch drivers control the N-

channel gates for supply voltages ranging from 3V to 12V.

A programmable electronic circuit breaker protects against

shorts. Warning signals indicate that the circuit breaker

has tripped, a power failure has occurred or that the switch

drivers are turned off. The reset output can be used to

generate a system reset when the power cycles or a fault

occurs. The two connect inputs can be used with stag-

gered connector pins to indicate board insertion or re-

moval. The power-on reset input can be used to cycle the

board power or clear the circuit breaker.

The trip point of the ground sense comparator is set at

0.1V for LTC1421 and 2.5V for LTC1421-2.5.

The LTC1421/LTC1421-2.5 are available in 24-pin SO and

SSOP packages.

RAMP

CPON

COMP

–

COMP

REF

COMPOUT

PWRGD

RESET

CON2

AUXV

FAULT

POR

CON1

CCLO

SETLO GATELO V

OUTLO

LTC1421

GND DISABLE

CCHI

SETHI GATEHI V

OUTHI

0.1µF

1µF

16k

MTB50N06E

0.005Ω

171819202122

512

STAGGERED CONNECTOR

20k

7.15k

1/2 Si4936DY

0.47µF

0.025Ω

LOAD

–12V

12V

I/O

RESET

BEA

BEB

GND

µP

QS3384

QuickSwitch

QuickSwitch IS A REGISTERED TRADEMARK

OF QUALITY SEMICONDUCTOR CORPORATION.

1421 TA01

DATA BUS

PC BOARDBACKPLANE

DATA

BUS

GND

POR

FAULT

1µF

10k

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

Hot Swap is a trademark of Linear Technology Corporation.

DESCRIPTIO

FEATURES

APPLICATIO S

TYPICAL APPLICATIO

Summary of content (24 pages)

PAGE 1
LTC1421/LTC1421-2.5 Hot Swap Controller U FEATURES ■ ■ ■ ■ ■ ■ ■ ■ ■ DESCRIPTIO The LTC®1421/LTC1421-2.5 are Hot SwapTM controllers that allow a board to be safely inserted and removed from a live backplane. Using external N-channel pass transistors, the board supply voltages can be ramped up at a programmable rate. Two high side switch drivers control the Nchannel gates for supply voltages ranging from 3V to 12V.
PAGE 2
LTC1421/LTC1421-2.5 W U U U W W W ABSOLUTE MAXIMUM RATINGS PACKAGE/ORDER I FOR ATIO (Note 1) Supply Voltage (VCCLO, VCCHI, AUXVCC) .............. 13.2V Input Voltage (Analog Pins) ..... – 0.3V to (VCCHI + 0.3V) Input Voltage (Digital Pins) ................... – 0.3V to 13.2V Output Voltage (Digital Pins) .. – 0.3V to (VCCLO + 0.3V) Output Voltage (CPON) ......... – 13.2V to (VCCLO + 0.3V) Output Voltage (VOUTLO, VOUTHI) ........... – 0.3V to 13.2V Output Voltage (GATELO, GATEHI) ........... – 0.
PAGE 3
LTC1421/LTC1421-2.5 ELECTRICAL CHARACTERISTICS The ● denotes specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. VCCHI = 12V, VCCLO = 5V unless otherwise noted (Note 2). SYMBOL PARAMETER CONDITIONS MIN IRAMP RAMP Pin Output Current Charge Pump On, VRAMP = 0.
PAGE 4
LTC1421/LTC1421-2.5 U W TYPICAL PERFORMANCE CHARACTERISTICS Reference Voltage vs Temperature 1.238 1.245 24 VCCLO = 5V VCCHI = 12V 23 GATE VOLTAGE (V) 1.234 1.232 1.230 1.228 VCCLO = 5V VCCHI = 12V REFERENCE VOLTAGE (V) VCCLO = 5V VCCHI = 12V 1.236 REFERENCE VOLTAGE (V) Reference Voltage vs Source Current Gate Voltage vs Temperature 22 GATEHI 21 20 19 GATELO 1.226 50 25 75 0 TEMPERATURE (°C) 100 17 – 50 – 25 125 1.
PAGE 5
LTC1421/LTC1421-2.5 U W TYPICAL PERFORMANCE CHARACTERISTICS ICCLO Supply Current vs VCCLO Voltage CPON Voltage vs Source Current (Charge Pump On) 5 7 VCCLO = 5V VCCHI = 12V ICCLO SUPPLY CURRENT (mA) CPON VOLTAGE (V) 4 3 2 1 0 VCCHI = 12V 6 5 4 3 2 1 0 – 0.5 – 1.0 – 1.5 – 2.0 – 2.5 SOURCE CURRENT (mA) – 3.0 1421 G10 0 0 2 8 6 10 4 VCCLO VOLTAGE (V) 12 14 1421 G11 U U U PIN FUNCTIONS CON1 (Pin 1): TTL Level Input with a Pull-Up to VCCLO.
PAGE 6
LTC1421/LTC1421-2.5 U U U PIN FUNCTIONS RAMP (Pin 10): Analog Power-Up Ramp Control Pin. By connecting an external capacitor between the RAMP and GATEHI, a positive linear voltage ramp on GATEHI and GATELO is generated on power-up with a slope equal to 20µA/CRAMP. A 10k resistor in series with the capacitor enhances the ESD performance at the GATEHI pin. FB (Pin 11): Analog Feedback Input. FB is used to set the reset threshold voltage on VCCLO. For a 5V supply leave FB floating. For a 3.
PAGE 7
LTC1421/LTC1421-2.5 W BLOCK DIAGRAM VCC 24 23 22 19 18 21 10 17 16 20 VCCLO SETLO VCCHI SETHI GATELO RAMP GATEHI VOUTHI VOUTLO AUXVCC 50mV + – 50mV AUXVCC + – CHARGE PUMP N2 CP1 N1 CP3 CP2 + + – VCC UNDERVOLTAGE LOCKOUT 73.5k + – VTRIP CP4 71.5k – 9 CPON FB 11 REF 8 PWRGD 6 RESET 7 26.7k + 1.
PAGE 8
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION Hot Circuit Insertion 12V When circuit boards are inserted into a live backplane, the supply bypass capacitors on the board can draw huge transient currents from the backplane power bus as they charge up. The transient currents can cause permanent damage to the connector pins and cause glitches on the system supply, causing other boards in the system to reset.
PAGE 9
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION PWRGD and RESET The LTC1421 uses a 1.232V bandgap reference, internal resistive divider and a precision voltage comparator to monitor VOUTLO (Figure 6). The reset threshold voltage for VOUTLO is determined by the FB pin connection as summarized in Table 1. VOUTLO VCCLO 20µA 73.5k 71.5k COMP1 – PWRGD FB VCCLO 26.
PAGE 10
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION Figure 8c shows how the comparator can be used to generate a reset when the 12V supply (VOUTHI) drops below 10.8V. The 5V supply (VOUTLO) also generates a reset when it dips below 4.65V. When the 12V supply drops below 10.8V, COMPOUT will pull the FB pin low setting the internal threshold voltage for comparator 1 to 5.88V. Since VOUTLO is less than 5.88V, PWRGD immediately goes low and a reset is generated 32µs later. A 5.
PAGE 11
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION is connected between REF (Pin 8) and the negative supply and the trip point of Comparator 2 set to GND. Soft Reset Generation A soft reset that doesn’t cycle the supply voltage can be generated externally using Pin 11 (FB) as shown in Figure 9. For a 5V supply the FB pin is left floating to set the internal supply monitor trip voltage to 4.65V.
PAGE 12
LTC1421/LTC1421-2.5 U W U U APPLICATIONS INFORMATION When VCCLO collapses, there is enough energy stored on the 1µF capacitor connected to AUXVCC to keep the gate discharge circuitry alive long enough to fully turn off the external N-channels. CONNECTOR VCC DATA BUS Power N-Channel Selection D1 OUT D2 BACKPLANE BOARD 1421 F12 The RDS(ON) of the external pass transistor must be low enough so that the voltage drop across it is about 200mV or less at full current.
PAGE 13
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION can usually be prevented by using logic that does not include the clamping diodes such as the QSI 74FCTT family from Quality Semiconductor, or by using a data bus switch such as the 10-bit QS3384 QuickSwitch also from Quality Semiconductor (Tel: 408-450-8000). The QuickSwitch bus switch contains an N-channel placed in series with the data bus. The switch is turned off when the board is inserted and then enabled after the power is stable.
PAGE 14
LTC1421/LTC1421-2.5 U W U U APPLICATIONS INFORMATION up sequence will begin automatically. The trip point potential for LTC1421 is set at 0.1V and 2.5V for LTC1421-2.5. When CON1 and CON2 are both forced to ground for more than 20ms, the LTC1421 assumes that the board is fully connected to the host and power-up can begin. When VCCLO and VCCHI exceed the 2.
PAGE 15
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION time point 2). Pulses less than 20ms on POR are ignored. CPON goes low. Both GATEHI and GATELO will be actively pulled down to GND. When VOUTLO drops below its reset threshold voltage, PWRGD will immediately pull low (time point 3) followed by RESET and DISABLE 32µs later (time point 4). Both supplies will be discharged to ground and stay there until POR is pulled high. The circuit breaker can be reset by pulling POR low.
PAGE 16
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION Board Removal Timing time for power fail information to be stored in nonvolatile memory, the falling edge of RESET (time point 3) is delayed by 32µs from the falling edged of PWRGD. When the board is removed from the host, the sequence happens in reverse (Figure 17). Since CON1 and CON2 are the shortest pins, they break connection first and are internally pulled high (time point 1). The charge pumps are turned off, CPON is pulled low.
PAGE 17
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION 5V Only Applications will pull the POWERGOOD signal low as long as the supply remains above 4.65V. Note that a soft reset will not affect the POWERGOOD signal. The FAULT signal is also monitored to determine that the circuit breaker has tripped. The LTC1421 may be used in 5V only applications as shown in Figure 18. A soft reset can be generated from the backplane via an open-collector inverter driving the FB (Pin 11) or by a push button to ground.
PAGE 18
LTC1421/LTC1421-2.5 U W U U APPLICATIONS INFORMATION module. The ground pin for the LTC1421 is connected to – 48V; Zener diode D1 and resistor R1 provide the positive supply for the chip. Bypass capacitor C4 is protected against inrush current by P-channel Q1. When the board is inserted into the backplane, transistor Q1 is turned off by resistor R2.
PAGE 19
BACKPLANE – 48V – 48V STAGGERED CONNECTOR PC BOARD D1 5.1V S1 – 48V + R1 5.1k 1W C1 1µF 3 1 4 2 24 C2 2.2µF 25V + 12 13 14 8 11 15 6 7 10 9 R4 300Ω 1/8W 1µF R2 15k 1/8W Q2 MPSA06 R3 56k 1/2W R6 402Ω 1/8W R5 10k 1/2W + + C5 4.7µF 50V C4 4.7µF 50V + R8 1k 1/8W 3 C6 100µF 100V SW GND 4 R10 4.32k 1/8W R13 1.24k 1/8W D4 Q3 Q4 MBR3100 2N5401 2N5401 D3 MBR3100 C9 0.33µF 50V R9 1k 1/8W 1 FB VC LT1170HVCT VCC 5 D2 7.5V L1 100µH Figure 20.
PAGE 20
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION – 48V R1 5.1k 23 D1 4.3V STAGGERED CONNECTOR 22 19 5V 10A 17 18 11 R3 10k + 4.7k 1 + VICOR VI-J30-CY 100µF 100µF 0.1µF LTC1421 12 0.1µF – 8 24 3 13 2 15 GATE IN – 1µF 14 R2 300Ω 1N4148 C1 0.1µF – 48V 4N25 100Ω Q1 BACKPLANE 1421 F21 PC BOARD Figure 21. – 48V to 5V Hot Swappable Supply Q1 IRFR9110 24V C3 2.2µF 25V STAGGERED CONNECTOR R1 5.1k 1/4W + D1 5.
PAGE 21
BACKPLANE 5V STAGGERED CONNECTOR PC BOARD 12 LTC1421 6 7 8 14 13 15 9 10 11 10k S2 1µF C2 0.1µF R5 16V 510Ω 5% R4 10k 1% R8 100k 1% R9 26.7k 1% C10 1µF 16V R10 10k 5% + C4 0.1µF 16V C8 220pF CERAMIC C7 4700pF CERAMIC C3 220µF 16V ×4 6 5 7 2 SHDN G1 VCC PVCC1 C5 10µF 16V 4 1 C6 0.1µF 16V Q2 MTD20N03HL D1 1N4148 FB COMP R7 3 8 GND G2 7.5k 5% LTC1430CS8 + R6 22Ω 5% Figure 23. 5V to 3.
PAGE 22
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION R1 0.005Ω 1 1W 2 5V 3 Q1 MTB50N06E STAGGERED CONNECTOR 22 21 20 19 18 17 16 + C2 1µF C1 1µF 13 14 8 11 15 6 LTC1421 4 3 1 5 7 C3 0.47µF – 48V 2 +IN +OUT ASTRODYNE ASD10-48D12 –IN – OUT CONTROL 6 1µF R3 340Ω 1/8W R5 4.3k 1/8W Q3 2N5401 S1 12 1 C5 220µF 100V 10 9 2 24 CLOAD R7 1k 1/8W 10k 23 5V 8A + 4 R4 10k 1/8W R6 15k 1/8W 1421 F24 IRF530 BACKPLANE PC BOARD Figure 24.
PAGE 23
LTC1421/LTC1421-2.5 U U W U APPLICATIONS INFORMATION R2 0.005Ω 1W 1 2 5V 3 3 CLOAD STAGGERED CONNECTOR 10k 4 LTC1421 2 S1 C2 0.1µF 24V 10 11 6 7 8 14 13 15 9 24 3 C5 0.1µF 25V 21 20 19 18 17 16 1 5 3.3V 8A + 1k C1 1µF 16V CLOAD R3 1M 5%,1/8W 0.047µF 4 23 22 5V 8A + 4 R1 0.005Ω Q1 1 1W 2 MTB50N06E 3.3V Q2 MTB50N06E 12 R5 330k 1% 1/16W R4 1k 5% 1/16W VCC µP RESET GND 1µF R6 200k 1% 1/16W 1421 F26 BACKPLANE PC BOARD Figure 26.
PAGE 24
LTC1421/LTC1421-2.5 U TYPICAL APPLICATION 1 12V 500mA 3 3.3V 7.5A PCI CONNECTOR Q3 2 1/2 IRF7101 R2 0.015Ω 5% 1W 4 R4 30Ω R10 100k R11 10Ω 1 2 4 R1 0.005Ω 5% 1/2W 3 23 R14 5.1k 22 R12 10Ω 21 10k 20 19 18 17 16 10 1 7 LTC1421 PCI POWER CONTROLLER C1 1µF 16V R6 100Ω 1% 1/16W R13 5.1k 6 1µF 8 14 3 ON/OFF C2 0.22µF 25V 11 24 5 3.3V 11.5A CIRCUIT BREAKER 5V 10A CIRCUIT BREAKER Q1 IRF7413 4 FAULT Q4 IRF7413 4 3 5V 5A 12V 3.3A CIRCUIT BREAKER R3 0.