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LT1641-1/LT1641-2

164112fc

Positive High Voltage

Hot Swap Controllers

The LT

1641-1/LT1641-2 are 8-pin Hot Swap

control-

lers that allow a board to be safely inserted and removed

from a live backplane. Using an external N-channel pass

transistor, the board supply voltage can be ramped up at

a programmable rate. A high side switch driver controls an

N-channel gate for supply voltages ranging from 9V to

80V.

The chips feature a programmable analog foldback cur-

rent limit circuit. If the chips remain in current limit for

more than a programmable time, the N-channel pass

transistor is either latched off (LT1641-1) or is set to

automatically restart after a time-out delay (LT1641-2).

The PWRGD output indicates when the output voltage,

sensed by the FB pin, is within tolerance. The ON pin

provides programmable undervoltage lockout.

The LT1641-1/LT1641-2 are available in the 8-lead SO

package.

■

Hot Board Insertion

■

Electronic Circuit Breaker

■

Industrial High Side Switch/Circuit Breaker

■

24V/48V Industrial/Alarm Systems

■

Allows Safe Board Insertion and Removal from a

Live Backplane

■

Controls Supply Voltage from 9V to 80V

■

Programmable Analog Foldback Current Limiting

■

High Side Drive for an External N-Channel

■

Latched Operation Mode (LT1641-1)

■

Automatic Retry (LT1641-2)

■

User Programmable Supply Voltage Power-Up Rate

■

Undervoltage Lockout

■

Overvoltage Protection

■

Both are available in 8-Lead SO Package

*SMAT70A

*DIODES, INC.

24V

SHORT

GND

TIMER

SENSE GATE

CMPZ

5248B

GND

PWRGD

10Ω

49.9k

1641-1 TA01

3.4k

0.68µF

R6,

1k, 5%

0.01Ω

10nF

59k

3.57k

24k

OUT

LT1641-1/LT1641-2

IRF530

24V Input Voltage Application

APPLICATIO S

FEATURES

TYPICAL APPLICATIO

DESCRIPTIO

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

All other trademarks are the property of their respective owners.

Summary of content (12 pages)

PAGE 1
LT1641-1/LT1641-2 Positive High Voltage Hot Swap Controllers U FEATURES DESCRIPTIO ■ The LT®1641-1/LT1641-2 are 8-pin Hot SwapTM controllers that allow a board to be safely inserted and removed from a live backplane. Using an external N-channel pass transistor, the board supply voltage can be ramped up at a programmable rate. A high side switch driver controls an N-channel gate for supply voltages ranging from 9V to 80V.
PAGE 2
LT1641-1/LT1641-2 U W W W ABSOLUTE AXI U RATI GS (Note 1) Supply Voltage (VCC) ...............................– 0.3V to 100V Input Voltage (SENSE) .............................– 0.3V to 100V Input Voltage (TIMER) ...............................– 0.3V to 44V Input Voltage (FB, ON) ...............................– 0.3V to 60V Output Voltage (PWRGD) ........................– 0.3V to 100V Output Voltage (GATE) ............................– 0.3V to 100V Operating Temperature Range LT1641-1C, LT1641-2C ...
PAGE 3
LT1641-1/LT1641-2 AC ELECTRICAL CHARACTERISTICS TA = 25°C, VCC = 24V SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS tPHLON ON Low to GATE Low Figures 1, 2 6 µs tPLHON ON High to GATE High Figures 1, 2 1.7 µs tPHLFB FB Low to PWRGD Low Figures 1, 3 3.2 µs tPLHFB FB High to PWRGD High Figures 1, 3 tPHLSENSE (VCC – SENSE) High to GATE Low Figures 1, 4 µs 1.5 0.5 Note 1: Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.
PAGE 4
LT1641-1/LT1641-2 U W TYPICAL PERFOR A CE CHARACTERISTICS Gate Drive vs Temperature 16 15 14 GATE DRIVE (VGATE – VCC) (V) VCC = 48V 13 12 11 10 9 8 VCC = 10.8V 7 TA = 25°C 14 12 10 8 0 25 50 TEMPERATURE (°C) 75 0 100 20 40 VCC (V) 60 TA = –45°C TA = 0°C 10 TA = 25°C TA = 85°C 6 70 90 1.330 1.325 1.320 1.315 1.310 1.305 1.300 1.295 1.290 1.285 –50 ON Pin Voltage Hysteresis vs Temperature –25 0 25 50 TEMPERATURE (°C) 75 1.233 1.231 1.229 1.227 1.225 1.223 –50 0.080 0.070 0.
PAGE 5
LT1641-1/LT1641-2 U U U PI FU CTIO S ON (Pin 1): The ON pin is used to implement undervoltage lockout. When the ON pin is pulled below the 1.233V Highto-Low threshold voltage, an undervoltage condition is detected and the GATE pin is pulled low to turn the MOSFET off. When the ON pin rises above the 1.313V Low-to-High threshold voltage, the MOSFET is turned on again. Pulsing the ON pin low after a current limit fault will reset the fault latch and allow the part to turn back on.
PAGE 6
LT1641-1/LT1641-2 W BLOCK DIAGRA VCC SENSE VP VP GEN FB – 12mV ~ 47mV CHARGE PUMP AND GATE DRIVER + + REF GEN 0.5V GATE + – PWRGD 1.233V 1.233V – + ON – VCC – 8.3V + UNDERVOLTAGE LOCKOUT LOGIC + 0.5V VP – 80µA + 1.
PAGE 7
LT1641-1/LT1641-2 W UW TI I G DIAGRA S 1.313V 1.313V 1.233V ON tPLHON FB 1.233V tPLHFB tPHLON tPHLFB 1V 1V PWRGD GATE 5V 1V 1641-1 F03 1641-1 F02 Figure 2. ON to GATE Timing Figure 3. FB to PWRGD Timing VCC – SENSE 47mV tPHLSENSE VCC GATE 1641-1 F04 Figure 4.
PAGE 8
LT1641-1/LT1641-2 U W U U APPLICATIO S I FOR ATIO RS 0.025Ω VIN 24V Q1 IRF530 SHORT PIN D1 CMPZ 5248B R5 10Ω 5% R1 49.9k 1% VOUT CL R3 59k 1% C1 R6, 10nF 1k, 5% 8 VCC 1 7 6 SENSE GATE R7 24k 5% FB ON 2 R4 3.57k 1% LT1641-1 R2 3.4k 1% PWRGD TIMER 3 PWRGD GND 5 GND + 4 C2 0.68µF 1641-1 F05 Figure 5.
PAGE 9
LT1641-1/LT1641-2 U U W U APPLICATIO S I FOR ATIO VCC – VSENSE PROPAGATION DELAY 12µs 10µs 47mV 8µs 6µs 4µs 2µs 12mV 0V 0.5V VFB 50mV 100mV 150mV 200mV 1641-1 F07 Figure 7. Current Limit Sense Voltage vs Feedback Pin Voltage current source. When the TIMER pin falls below 0.5V, the GATE pin either turns on automatically (LT1641-2) or once the ON pin is pulsed low to reset the internal fault latch (LT1641-1).
PAGE 10
LT1641-1/LT1641-2 U W U U APPLICATIO S I FOR ATIO RS 0.025Ω VIN 24V Q1 IRF530 SHORT PIN R1 49.9k 1% D1 CMPZ 5248B R5 10Ω 5% 8 VCC 7 R7 24k 5% SENSE GATE FB 2 R4 3.57k 1% LT1641-1 R2 3.4k 1% PWRGD TIMER 3 PWRGD GND 5 Figure 9. Short-Circuit Waveforms CL R3 59k 1% 6 ON GND VOUT C1 R6, 10nF 1k, 5% D2 30V 1N5256B 1 + 4 C2 0.68µF 1641-1 F10 Figure 10. Overvoltage Detection Figure 11. Overvoltage Waveforms GATE Pin Voltage A curve of gate drive vs VCC is shown in Figure 13.
PAGE 11
LT1641-1/LT1641-2 U U W U APPLICATIO S I FOR ATIO Layout Considerations high current applications. To improve noise immunity, put the resistor divider to the ON pin close to the chip and keep traces to VCC and GND short. A 0.1µF capacitor from the ON pin to GND also helps reject induced noise. Figure 14 shows a layout that addresses these issues. To achieve accurate current sensing, a Kelvin connection is recommended. The minimum trace width for 1oz copper foil is 0.
PAGE 12
LT1641-1/LT1641-2 U PACKAGE DESCRIPTIO S8 Package 8-Lead Plastic Small Outline (Narrow .150 Inch) (Reference LTC DWG # 05-08-1610) .189 – .197 (4.801 – 5.004) NOTE 3 .045 ±.005 .050 BSC 8 .245 MIN 7 6 5 .160 ±.005 .150 – .157 (3.810 – 3.988) NOTE 3 .228 – .244 (5.791 – 6.197) .030 ±.005 TYP 1 RECOMMENDED SOLDER PAD LAYOUT .010 – .020 × 45° (0.254 – 0.508) .008 – .010 (0.203 – 0.254) .053 – .069 (1.346 – 1.752) 0°– 8° TYP .016 – .050 (0.406 – 1.270) NOTE: 1. DIMENSIONS IN .014 – .019 (0.