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LINEAR TECHNOLOGY LTC1645 User Guide Manual

Summary

The LTC1645 is a robust dual-channel Hot Swap Controller designed to ensure safe board insertion and removal from live backplanes. This advanced power sequencer provides programmable supply voltage ramping for supplies ranging from 1.2V up to 12V, managing system power-up and power-down rates precisely using external N-channel FETs. The accompanying manual details critical features, including Undervoltage Lockout (UVLO), electronic circuit protection, and glitch filtering, making it ideal for engineers building reliable embedded systems requiring meticulous power management during operation.

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Page 1 Text Content

LTC1645

CO NN EC TO

Dual-Channel Hot Swap

CO NN EC TO

Controller/Power Sequencer

FEATURES DESCRIPTIO

Allows Safe Board Insertion and Removal from a The LTC®1645 is a 2-channel Hot Swap TM controller that Live Backplane allows a board to be safely inserted and removed from a Programmable Power Supply Sequencing live backplane. Using external N-channel pass transistors, Programmable Electronic Circuit Breaker the supply voltages can be ramped at a programmable User-Programmable Supply Voltage Power-Up and rate. Two high side switch drivers control the N-channel Power-Down Rate gates for supply voltages ranging from 1.2V to 12V. The High Side Drivers for External N-Channel FETs two channels can be set to ramp up and down separately, Controls Supply Voltages from 1.2V to 12V or they can be programmed to rise and fall simultaneously, Ensures Proper Power-Up Behavior ensuring power supply tracking at the two outputs.

Undervoltage Lockout

Programmable electronic circuit breakers protect against

Glitch Filter Protects Against Spurious RESET Signals

shorts at either output. The RESET output can be used to

8- and 14-Pin SO Packages

generate a system reset when a supply voltage falls below a user-programmed voltage. An additional spare com-

APPLICATIO S

parator is available for monitoring a second supply voltage.

Hot Board Insertion

Power Supply Sequencing The LTC1645 is available in the 8- and 14-pin SO packages. Electronic Circuit Breaker , LTC and LT are registered trademarks of Linear Technology Corporation. Hot Swap is a trademark of Linear Technology Corporation.

TYPICAL APPLICATIO

5V and 3.3V Hot Swap 5V and 3.3V Hot Swap Waveforms

IRF74130.005Ω* VOUT2 VIN2 3.3V 5A CLOAD2

ON VOUT1 5V/DIV

0.005Ω* IRF7413

VIN1 5V 5A 10Ω CLOAD1

GATEn

10V/DIV

VOUT2 5V/DIV

SENSE1 VCC2GATE1 SENSE2 GATE2

VOUT1

LTC1645 5V/DIV (8-LEAD)

ON ON

1645 TA01

PLUG-IN CARDBACKPLANE *LRF1206-01-R005-J (IRC)

1645fa

Page Summary Contents For LINEAR TECHNOLOGY LTC1645 User Guide Manual

Page 1 LTC1645 CO NN EC TO Dual-Channel Hot Swap CO NN EC TO Controller/Power Sequencer FEATURES DESCRIPTIO Allows Safe Board Insertion and Removal from a The LTC®1645 is a 2-channel Hot Swap TM controller t...
Page 2 LTC1645 ABSOLUTE AXI U RATI GS (Note 1) Supply Voltage (VCC1, VCC2) 13.2V Output Current Input Voltage GATE1, GATE2 ±20m A FB, ON, COMP+ –0.3V to (VCC1 + 0.3V) Operating Temperature Range TIMER –0.3V ...
Page 3 LTC1645 ELECTRICAL CHARACTERISTICS The ● denotes the specifications which apply over the full operating temperature range, otherwise specifications are at TA = 25°C. 2.375V ≤ VCC1 ≤ 12V, 1.2V ≤ VCC2 ≤...
Page 4 OU TP UT OL TA GE (m V) GA TE (V LTC1645 TYPICAL PERFOR A CE CHARACTERISTICS Glitch Filter Time GATE Voltage vs Supply Voltage GATE Voltage vs Temperature vs Feedback Transient 16.0 TA = 25°C VCC1 = 5...
Page 5 LTC1645 PI FU CTIO S (14-Lead Package/8-Lead Package) VCC2 (Pin 1/Pin 1): Positive Supply Input. VCC2 can range An external pull-up is required to generate a logic high at from 1.2V to 12V for normal ...
Page 6 LTC1645 PI FU CTIO S (14-Lead Package/8-Lead Package) Whenever the timer is inactive, an internal N-channel FET the circuit breaker trips or the undervoltage lockout circuit shorts the TIMER pin to gr...
Page 7 LTC1645 APPLICATIO S I FOR ATIO Hot Circuit Insertion Power Supply Tracking and Sequencing When a circuit board is inserted into a live backplane, the Some applications require that the potential diff...
Page 8 LTC1645 APPLICATIO S I FOR ATIO Power Supply Ramping The ramp time for each supply is t = (VCCn • Cn)/10µA. If the ON pin is pulled below 2V for GATE2 or 0.8V for GATE1 The power supplies on a board a...
Page 9 LTC1645 4V /D IV APPLICATIO S I FOR ATIO No bulk capacitance is present to slow the rate of rise and and GND, then repeatedly inserting the circuit board into heavily damp the parasitic resonance. Ins...
Page 10 LTC1645 2V /D IV APPLICATIO S I FOR ATIO BA CK PL AN CO NN EC TO 0.01Ω IRF7413 CLOAD PC ED GE ON NE CT OR POWER LEADS +– LTC1645 1645 F06 BA CK PL AN CO NN EC TO 1µs/DIV 1645 F06a ON SEMICONDUCTOR * 1...
Page 11 LTC1645 APPLICATIO S I FOR ATIO 5A /D IV A/ DI Supply Glitching trips. The partially enhanced FET is easily disconnected without any supply glitch. LTC1645 Hot Swap circuits on the backplane are gener...
Page 12 LTC1645 APPLICATIO S I FOR ATIO nearly unlimited current flow. The LTC1645 discharges Glitch Filter the GATE pin in a few microseconds, but during this The LTC1645 has a glitch filter to prevent RESET...
Page 13 LTC1645 APPLICATIO S I FOR ATIO voltage on the external capacitor CTIMER starts to ramp up the ON pin below 0.4V and then high as shown at time with a slope dv/dt = 2µA/CTIMER. When the voltage reache...
Page 14 LTC1645 APPLICATIO S I FOR ATIO An external hard reset is initiated at time point 6. The ON Time points 16 to 19 show the same power-up sequence pin is forced below 0.8V but above 0.4V, and the GATEn ...
Page 15 LTC1645 APPLICATIO S I FOR ATIO VIN2 5V/DIV VIN1 5V/DIV VOUT2 5V/DIV VOUT1 5V/DIV TIMER 2V/DIV RESET 5V/DIV Figure 16. Ramping 3.3V and 2.5V Up and Down Together This circuit guarantees that: (1) VOUT...
Page 16 LTC1645 APPLICATIO S I FOR ATIO BOTH CURRENT LIMITS: 10A 0.005Ω* IRF7413 VOUT2 CLOAD2 0.005Ω* IRF7413 VOUT1 CLOAD1 VCC1 SENSE1 VCC2 SENSE2 GATE2GATE1 1% COMP+ RHYST LTC1645 (14-LEAD) COMPOUT µP RESET2...
Page 17 LTC1645 APPLICATIO S I FOR ATIO Using the LTC1645 as a Linear Regulator goes high which turns on Q3. This lowers the voltage on the gate of Q2. This feedback loop is compensated by This application us...
Page 18 LTC1645 APPLICATIO S I FOR ATIO Switching Regulator Supply Sequencing Switching Regulator Hot Swapping Figure 21 shows the LTC1645 sequencing two power High current switching regulators usually requir...
Page 19 LTC1645 APPLICATIO S I FOR ATIO SE NS E2 Q2 0. 1/ Si DY UT 1µ 6. 3V OA D2 BR T1 LT C1 0A CS 0p .5 PV CC PV CC G2 G1 Si DY .9 CD RH R4 SE NS E1 Q1 SH DN FB 0. EG OU 1/ Si DY UT CO GN OA D1 Si DY 6. 3V ...
Page 20 LTC1645 0. 3Ω FD B8 0L EG IN APPLICATIO S I FOR ATIO 3. 3V µF IR F7 6. 3V IR F7 Q2 EG OU FD B8 0L UT 2. 5V IR F7 5. 1Ω1. µF IR F7 6. 3V 1µ OA D2 BR LT G1 G2 PV CC PV CC GN 1% FB LT C1 SH DN AX R2 3. 0...
Page 21 LTC1645 APPLICATIO S I FOR ATIO Table 1. N-Channel Selection Guide ON CURRENT PART 2V/DIV LEVEL NUMBER MANUFACTURER DESCRIPTION 1A to 2A NDH8503N Fairchild Dual N-Channel RDS(ON) = 0.033 VREGIN 2V/DIV...
Page 22 LTC1645 PACKAGE DESCRIPTIO S8 Package 8-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) NOTE 3 .050 BSC MIN .150 – .157 NOTE 3 .030 ±.005 TYP RECOMMENDED SOLDER PAD LAYOUT (0.203 – 0....
Page 23 LTC1645 PACKAGE DESCRIPTIO S Package 14-Lead Plastic Small Outline (Narrow 0.150) (LTC DWG # 05-08-1610) .050 BSC NOTE 3 .228 – .244 .150 – .157 (5.791 – 6.197) (3.810 – 3.988) NOTE 3 .030 ±.005 TYP R...
Page 24 LTC1645 TYPICAL APPLICATIO Dual Supply Hot Swap with Tracking Outputs BOTH CURRENT LIMITS: 5A 0.01Ω* 1/2 Si4920DY VOUT1 1N4002 CLOAD1 D3 Q2 10Ω MBR0530T1D2 0.01Ω* 1/2 Si4920DY 1N4002 VOUT2 CLOAD2 1% V...

Manual Details

Brand Linear
Pages 24
File Size 325.03 KB
Published June 01, 2026
82 views

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Frequently Asked Questions

What does the LTC1645 control?

It is a 2-channel Hot Swap controller that controls supply voltages ranging from 1.2V to 12V.

How does this device ensure safe board insertion/removal?

It allows for safe connection and disconnection of a board from a live backplane using external N-channel pass transistors.

What protection features are included in the LTC1645?

Features include Undervoltage Lockout, proper power-up behavior checks, Glitch Filter protection against spurious signals, and programmable circuit breakers.

Can I customize the power sequencing rates?

Yes, the supply voltages can be programmed to ramp up and down at a programmable rate using two dedicated high side switch drivers.