FEATURES Fully Sequence Four Supplies Six with Minimal External Circuitry Cascadable for Additional Supplies Power Off in Reverse Order or Simultaneously Charge Pump Drives External MOSFETs Drives Power Supply Shutdown Pins with No External Pull-Up Resistors Sequence and Monitor Two or More Supplies 10µA Output Current Allows Soft-Starting of Supplies Done Indicator for Both Power On and Power Off Adjustable Time Delay Between Power Supplies Power Good Timer Power Supply Voltage Monitoring and Power Sequence Error Detection and Reporting Available in a 16-Lead Narrow SSOP Package APPLICATIO S U Sequenced Power Supplies for ASICs with Multiple I/O and Core Voltages Latch-Up Prevention in Systems with Multiple Power Supplies Quad Power Supply Sequencer DESCRIPTIO U The LTC 2924 is a power supply sequencer designed for use with external N-channel MOSFETs or power supplies with shutdown pins. Four power supplies can be fully sequenced by a single and up to five supplies can be sequenced to a sixth master supply. The requires a minimum of external components, using only two feedback resistors per sequenced power supply and a single resistor to set hysteresis. An internally regulated charge pump provides gate drive voltages for external logic and sub-logic-level MOSFETs. Adding a single capacitor enables an adjustable time delay between power supplies during both Power On and Power Off sequencing. A second capacitor can be added to enable a power good timer for detecting the failure of any power supply to turn on within the selected time. Errors in power supply sequencing and the control input are detected and reported at the output. The features precision input comparators which can provide 1% accuracy in monitoring power supply voltages. Multiple s may be easily cascaded to sequence a virtually unlimited number of power supplies., LTC and LT are registered trademarks of Linear Technology Corporation. All other trademarks are the property of their respective owners. TYPICAL APPLICATIO 1V 3V Q1 Q2 Q3 U Series MOSFET Power Supply Sequencer V = 0.93V V OFF = 0.91V V = 2.79V V OFF = 2.73V V = 4.21V V OFF = 3.76V 2V/DIV 10V/DIV 2V/DIV 2V/DIV Power-Up Sequence 3.3V 1V DE EARLY Q4 52.3k 45.3k 6.04k 1.62k V = 3.32V V OFF = 2.80V 25ms/DIV 2924 TA02b Power-Down Sequence SYSTEM CTROLLER DE HYS/CFG PGT 11.8k 49.9k 7.68k 1.69k Q1-Q4: IRL3714S ALL RESISTORS 1% 3.09k 2V/DIV 10V/DIV 2V/DIV 2V/DIV 3.3V 1V DE 2924 TA02a 25ms/DIV 2924 TA02c 1
ABSOLUTE AXI U RATI GS W W W (Note 1) Supply Voltage ( )... 0.3V to 6. Input Voltages, -... 0.3V to + 0.3V PGT,, HYS/CFG... 0.3V to + 0.3V Open-Drain Output Voltages, DE... 0.3V to + 0.3V Output Voltages (-) (Note 5)... 0.3V to + 4. Operating Temperature Range C... 0 C to 70 C I... 40 C to 85 C Storage Temperature Range... 65 C to 150 C Lead Temperature (Soldering, 10 sec)... 300 C U U U W PACKAGE/ORDER I FOR ATIO 1 2 3 4 5 6 7 8 TOP VIEW GN PACKAGE 16-LEAD PLASTIC SSOP T JMAX = 125 C, θ JA = 130 C/W 16 15 HYS/CFG 14 13 12 PGT 11 10 DE 9 ORDER PART NUMBER CGN IGN GN PART MARKING 2924 2924I Consult LTC Marketing for parts specified with wider operating temperature ranges. ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T A = 25 C. = 3V to 6V, unless otherwise noted. SYMBOL PARAMETER CDITIS MIN TYP MAX UNITS Supply Input Supply Range 3 6 V I CC Input Supply Current 1.5 3 ma Threshold V (TH), Low to High Threshold 0.6000 0.6060 0.6121 V V OFF(TH), High to Low Threshold 0.6014 0.6074 0.6135 V - Threshold V (TH) - Low to High Threshold 0.6020 0.6081 0.6142 V V OFF(TH) - High to Low Threshold 0.6026 0.6087 0.6148 V, - Characteristics V, - High Speed Low Fault Threshold 0.33 0.4 0.48 V I (HYS), - Hysteresis Current Range V V (TH) (Note 2) 0.5 50 µa I (ERROR), - Hysteresis Current Error 1 (I (HYS) /(0.5/R HYS )), V (TH) = 1V 0.5µA I < 25µA ±22 % 25µA I 50µA ±10 % I LEAK, - Leakage (Below Threshold) V (TH) = 0. 2 ±100 na V (HYS), - Minimum Hysteresis Voltage I HYS R HYS 4 mv - Characteristics V OUT(EN) - Gate Drive Voltage I OUTn = 0 + 4.5 + 6 V I OUT(EN) - On Current OUTn On, V OUT = ( + 4V) 8.6 10 11.2 µa R OUT(OFF) - Off Resistance to OUTn Off, I OUT = 2mA 240 Ω HYS Characteristics R HYS HYS Current Programming Resistor Range (Notes 2, 3) 1M Ω V HYS HYS Programming Voltage R HYS Tied to 0.5 V R HYS Tied to 0.5 V 2
ELECTRICAL CHARACTERISTICS The denotes the specifications which apply over the full operating temperature range, otherwise specifications are at T A = 25 C. = 3V to 6V, unless otherwise noted. SYMBOL PARAMETER CDITIS MIN TYP MAX UNITS Characteristics I Timer Pin Output Current Timer On V 0.9V 4 5 6 µa V TH(HI) Timer High Voltage Threshold = 0.93 1 1.07 V PGT Characteristics I PGT Power Good Timer Pin Output Current Power Good Timer On, V PGT 0.9V 4 5 6 µa V PGT Power Good Timer Fault Detected Voltage Threshold = 0.93 1 1.07 V DE Characteristics R D(LO) DE Pin Pull-Down Resistance to DE = Low, I = 2mA 100 Ω I D(HI) DE Pin Off Leakage Current DE = High 15 µa Characteristics R (LO) Pin Pull-Down Resistance to Being Pulled Low Internally, 400 Ω I = 2mA I (HI) Pin Off Leakage Current High 2 µa V (HI) Voltage Above Which an Externally Generated 1.6 V Condition Will Not be Detected V (LO) Voltage Below Which an Externally Generated 0.6 V Condition Will be Detected R F(EXT) External Pull-Up Resistance 10 kω t Externally Commanded Below V (LO) 1 µs to - Pull-Down On Delay t (MIN) Externally Commanded Minimum Time (Note 4) 1 µs Below V (LO) Note 1: Absolute Maximum Ratings are those values beyond which the life of a device may be impaired. Note 2: Hysteresis current must be 500nA minimum. Hysteresis current may exceed 50µA, but accuracy is not guaranteed. Note 3: HYS/CFG pin must be pulled to or with an external resistor. See Applications Information for details. Note 4: Determined by design, not production tested. External circuits pulling down on the pin must maintain the signal below V (LO) for 1µs. Note 5: Internal circuits may drive the OUTn pins higher than the Absolute Maximum Ratings. TYPICAL PERFOR A CE CHARACTERISTICS UW I CC vs V OUT(EN) vs I OUT V OUT(EN) vs I CC (ma) 2.3 2.1 1.9 1.7 1.5 I -4 = 10µA R HYS = 51k HIGH V OUT (V) 14 12 10 8 6 = 6V = 3V V OUT (V) 12 11 10 9 I -4 < 1µA 1.3 1.1 LOW 4 2 8 0.9 3 3.5 4 4.5 5 5.5 6 (V) E OUTPUT DRIVING CURRENT 0 0 2 4 6 8 10 12 I OUT (µa) 7 2 3 4 5 (V) 6 2924 G01 2924 G02 2924 G03 3
TYPICAL PERFOR A CE CHARACTERISTICS UW 55 R DE vs 200 R vs 50 180 R DE AT 2mA (Ω) 45 40 R AT 2mA (Ω) 160 140 120 35 100 30 3 4 5 6 (V) 80 3 4 5 6 (V) 2924 G04 2924 G05 OUTn (Off) I SAT vs Temperature OUTn (Off) I SAT vs 45 V OUT = 35 V OUT = 40 35 = 6V 30 I SAT (ma) 30 25 I SAT (ma) 25 20 20 15 = 3V 15 10 60 40 20 0 20 40 60 80 100 TEMPERATURE ( C) 10 2.5 3 3.5 4 4.5 5 5.5 6 6.5 (V) 2924 G06 2924 G07 4
PI FU CTIO S U U U - (Pins 1, 2, 3, 4): Sequenced Power Supply Monitor. Connect this pin to an external resistive divider between each sequenced power supply and. During Power On sequencing, (typ) at this pin indicates that the sequenced power supply (enabled with each of the - pins) has reached the desired Power On sequence voltage. A hysteresis current (programmed by the HYS pin) is sourced out of each of the - pins after the threshold is detected. During the Power Off sequence, at this pin indicates that the sequenced power supply has reached the desired Power Off voltage. The hysteresis current is removed after the threshold is detected. - (Pins 5, 6, 7, 8): Sequenced Power Supply Enable. Connect this pin to the shutdown pin or an external series N-channel MOSFET for each power supply being sequenced. (A low at this pin means the sequenced power supply is commanded to turn off.) When disabled, each output is connected to with a resistance of <240Ω. When enabled, each output is connected to an internally generated charge pump supply (nominally + ) via an internal 10µA (typ) current source. (Pin 9): Fault Pin. Pull this pin high with an external resistor. The will pull this pin low if a fault condition is detected (see Applications Information for details). Pulling this pin low externally causes a simultaneous unsequenced Power Off. DE (Pin 10): Done Pin. Pull this pin high with an external resistor. This open-drain output pulls low at the completion of the Power-On sequence. At the end of the Power Off sequence, the floats this pin. (Pin 11): Power Supply Input. All internal circuits are powered from this pin. should be connected to a low noise power supply voltage and should be bypassed with at least a capacitor to the pin in close proximity to the. PGT (Pin 12): Power Good Timer. The PGT pin sets the time allowed for a power supply to turn on after being enabled with the - pins. Connecting a capacitor between this pin and ground programs a 0.2µs/µF duration. The PGT pin is reset before each of the - pins are asserted. If the voltage at the PGT pin reaches 1V, a fault condition is asserted. The PGT pin must be connected directly to ground to disable the power good timer function. (Pin 13): Ground. All internal circuits are returned to the pin. Connect this pin to the ground of the power supplies that are being sequenced. (Pin 14): Timer. This pin sets the time delay between a supply ready (-) signal and the enabling of the next power supply in the sequence (-). Connecting a capacitor between this pin and ground programs a 0.2µs/µF duration. The pin may be left floating if no delay is required between supplies being sequenced on or off. If an internal fault condition occurs, will indicate so by going to until the fault condition is cleared. Do not connect any other circuits to the pin. HYS/CFG (Pin 15): Hysteresis Current Setting and Cascade Configuration. Connecting a resistor between this pin and programs a 0.5/R EXT (typ) hysteresis current which is sourced out of each IN and pin. When multiple s are cascaded, the HYS/CFG pin is also used to configure the position of the first. See Applications Information for details. (Pin 16): On Pin. Commands the to sequence the power supplies up (Power On sequence) or down (Power Off sequence). Typically connected to a system controller. Hysteresis current is applied to this pin when above (typ). This pin has a precision threshold and can be used to sense a nonsequenced power supply s voltage to start the Power On sequence. See Applications Information for details. For cascading multiple s, see Applications Information for connecting the pin. 5
FU CTIO AL DIAGRA U U W 11 I H V CP 16 + 10µA 5 I H V CP 1 I H + 1V 0. INTERNAL REFERENCE UVLO 10µA 6 2 + CLOCK V CP 10µA CHARGE PUMP V CP 7 I H 5 4 3 + LOGIC V CP 10µA 8 I H 4 + LAST DE 10 15 HYS/CFG I H FIRST DETECT 0. 9 5µA 5µA + + 14 1V 1V PGT 12 13 2924 BD 6
OPERATIO U PS1 V PS1() PS3 V PS3() PS2 V PS1(OFF) V PS2() PS4 V PS3(OFF) 0V V PS4() V PS4(OFF) V PS2(OFF) * DE * IS CAPACITOR ADJUSTABLE Figure 1. Power On and Power Off Sequence for Four Supplies 2924 F01 The is a power supply sequencer designed for use with external N-channel MOSFETs or power supplies with shutdown pins. Four power supplies can be fully sequenced by a single (see Figure 1). An internally regulated charge pump provides ( + ) gate voltages for driving external logic-level and sub-logic level MOSFETs. Adding a single capacitor enables an adjustable time delay between power supplies during both Power On and Power Off sequencing. A second capacitor can be added to enable a power good timer to detect the failure of any power supply to turn on within the set time. 1V The pin is used to command the to start the Power On and Power Down sequences. To command the Power On sequence, the pin is pulled above by a system controller or a resistive divider from a power supply. A voltage comparator senses the command and signals the sequencing logic to start the Power On sequence. When the Power On sequence starts, the grounding switch is released and a 5µA current source charges an external capacitor, C (see Figure 2). When the voltage on this capacitor exceeds 1V, a comparator signals the DE Figure 2. On Sequence for Four Supplies 2924 F02 7
OPERATIO U logic, which starts the charge pump and enables to turn on the first power supply. The power good timer circuit is also enabled by turning off the switch that is shorting the external capacitor to ground and enabling a 5µA current source to charge the C PGT capacitor. The output circuit responds by opening a switch, which is shorting the pin to ground and enabling a 10µA current source, which is connected to the charge pump. The pin can be connected to either the shutdown pin of a power supply or the gate of a N-channel MOSFET that is in series with the output of the sequenced power supply. As the power supply turns on, the resistive divider connected to the pin starts to drive up the voltage at the pin. When the voltage at this pin exceeds, the comparator signals the logic that the first power supply is on. At this time a current is sourced out of the pin which serves as the hysteresis current for the input comparator. This allows the application to choose a lower Power Off voltage sense during the Power Off sequence. The power good timer (PGT) circuit is signaled and resets the PGT capacitor. The timer circuit is enabled and the cycle repeats until the last power supply has turned on. When the last power supply has turned on, the DE pin pull-down switch is turned on to signal that the Power On sequence has completed. If a power supply fails to turn on after it is enabled and the voltage at the PGT pin exceeds 1V, the will disable all power supplies by pulling all OUT pins to ground. A fault condition will be indicated by the pin pulling low. The hysteresis current sourced at the pin and each IN pin is set at the HYS/CFG pin. The current is determined by an external resistor nominally pulled to ground. The hysteresis current is 0./R HYS. The Power Off sequence is initiated by pulling the pin below after a Power On sequence has completed (see Figure 3). The Power Off sequence turns off the power supplies in the reverse order of the Power On sequence. is turned off first. The timer function is used between each supply being sequenced down. The PGT is not used. The end of the Power Off sequence is indicated by the floating the DE pin. DE Figure 3. 4-Power Supply Power Off Sequence 2924 F03 8
APPLICATIO S I FOR ATIO U W U U Up to five supplies can be sequenced to a sixth master supply by a single (Figure 4). The turn on of the first power supply is sensed by the pin. Power supplies two through five are enabled by the through pins, and their turn on sensed by the through pins respectively. The last power supply is enabled by the DE pin, which is generally connected through an inverter. This application is used where power supplies are sequentially sequenced on and the turn off is simultaneous. Multiple s can be cascaded to facilitate sequencing of eight or more power supplies. See the Cascading Multiple s section. Selecting the Hysteresis Current and IN Pin Feedback Resistors The - pins are connected to a sequenced power supply with a resistive divider. The resistors are calculated by first selecting a hysteresis current, I HYS, and calculating R HYS : R HYS 05. V = ; 05. µ A IHYS 50µ A I HYS For each sequenced power supply, choose a voltage when the power supply is considered to be On during a Power On PS1 V OUT PS2 V OUT PS3 V OUT PS4 V OUT PS5 V OUT PS6 V OUT EARLY* SYSTEM CTROLLER TURN OFF * EARLY MUST BE BEFORE SEQUENCING SUPPLIES DE 2924 F04 Figure 4. Six Power Supply Sequencer Block Diagram 9
APPLICATIO S I FOR ATIO sequence (V ) and Off during a Power Off sequence (V OFF ). Referring to Figures 5 and 6, each set of resistors can then be calculated by: R R B A V VOFF = IHYS RB 061. V = V 061. V U W U U In the following example (Figure 5) I HYS is 50µA. This corresponds to a R HYS resistor of: I HYS IN + I HYS 2924 F05 Figure 5. Designing I HYS, Feedback Resistors R B R A V PS I RB V = 2.2V V OFF = 1V I FB = I RB + I HYS R HYS = 05. V k 50µ A = 10 Ω In Figure 5, V = 2.2V and V OFF = 1V. Using the equations provided above: R R B A 22. V 1V = = 24kΩ 50µ A 24kΩ 0. 61V = = 92. kω 22. V 061. V Hysteresis Voltage Check After calculating the resistors R B and R A, check to make sure the hystersis voltage at the - pins is greater than 4mV. Use the following equation: V VOFF RA VHYS RA + RB For this example: ( 22. V 1V ) 92. kω VHYS = V. kω + kω = 033. 92 24 which is greater than 4mV. = ( ) EARLY* SYSTEM CTROLLER POWER SUPPLY 1 POWER SUPPLY 2 POWER SUPPLY 3 POWER SUPPLY 4 3.3V * EARLY MUST BE BEFORE SEQUENCING SUPPLIES 1.6V 2. DE HYS/CFG PGT 24.9k 9.31k 49.9k 2924 TA03 15.8k 49.9k V 3.01V V OFF 2.68V V 4.49V V OFF 3.99V V 1.43V V OFF 1.27V V 2.2 V OFF 2V 33.2k 11.81k 7.87k 8.45k 10 Figure 6. Typical Power Supply Sequencer
APPLICATIO S I FOR ATIO Details of Resistor Calculations In this example, the voltage at the IN pins is when the detects that the power supply is On during a Power On sequence or Off during a Power Off sequence. The delta voltage, V, represents the difference: V = 2.2V 1V = 1.2V This delta voltage on R B will be equal to the hysteresis current I HYS. Therefore: R B = V V k I = 12. 50µ A = 24 Ω HYS The current I RB at the Power On voltage of 2.2V is: V V I RB = 22. 061. 24k = 66 µa During the Power On sequence, I HYS = 0, so I FB is equal to I RB and R A is: R A = 061. k 66µ A = 92. V OFF Precaution Use caution if designs call for V OFF voltages less than ~0.8V. Many loads stop using significant current below this level, and the power supply may take a long time to go below this voltage. If V OFF voltages at or less than this voltage are necessary, consider adding an extra resistive load at the output of the power supply to ensure it discharges in a reasonable amount of time. Selecting the Timing Capacitor During the Power On sequence, the timer is used to create a delay between the time one supply reaches the On threshold and the next supply is enabled. During the Power Off sequence, the timer is used to create a delay between the time one supply reaches the Off threshold and the next supply is disabled. Select the timing capacitor with the following equation: C (F) = t DELAY 5000 3 F/s U W U U Leaving the pin unconnected will generate the minimum delay. The accuracy of the time delay will be affected by the capacitor leakage (the nominal charge current is 5µA) and capacitor tolerance. A low leakage ceramic capacitor is recommended. Selecting the Power Good Timer (PGT) Capacitor During the Power On sequence, the PGT can be used to detect the failure of a power supply to reach the desired On voltage. The PGT is enabled each time a power supply is enabled by the - pins. The PGT is reset each time an - pin detects that a power supply is at the desired On voltage. Select the PGT timeout capacitor with the following equation: C PGT (F) = t PGT 5000 3 F/s If no PGT is desired, the PGT pin must be shorted to ground. The accuracy of the PGT timeout will be affected by the capacitor leakage (the nominal charge current is 5µA) and capacitor tolerance. A low leakage ceramic capacitor is recommended. Cascading Multiple s Two or more s may be cascaded to fully sequence 8,12 or more power supplies. Figures 7 and 8 show how to configure the to sequence 8 and 12 power supplies. To sequence more power supplies, use the circuit in Figure 8 and add more s in the middle. Notice that the last in the cascade string must have a pull-up resistor on the DE pin. Any that is not the first in the cascade string should have the hysteresis current setting resistor, R HYS, pulled to instead of ground. The value of the R HYS resistor remains unchanged. The pins should all be connected together and pulled up with a single resistor. All pins for the s in the cascade chain must be connected to the same power supply. 11
APPLICATIO S I FOR ATIO U W U U R HYS HYS/CFG HYS/CFG R HYS PGT PGT DE DE DE 2924 F07 Figure 7. Cascading Two s to Fully Sequence Up to Eight Power Supplies R HYS R HYS HYS/CFG HYS/CFG HYS/CFG R HYS PGT PGT PGT DE DE DE DE Figure 8. Cascading Three s to Fully Sequence Up to 12 Power Supplies 2924 F08 Cascade Handshaking PS1 When two or more chips are cascaded together they communicate using a combination of levels and pulses which do not look like the normal output of a DE pin nor input to an pin. Do not connect any other components to the node between the DE and pins. When laying out multiple s in the cascaded configuration, keep the parasitic capacitance on this node below 75pF. PS2 Connecting Unused OUT and IN Pins Figure 9 shows how to connect unused OUT and IN pins on the. Unused OUT-IN pairs must be connected together to ensure proper operation. 12 2924 F09 Figure 9. Connecting Unused OUT and IN Pins
APPLICATIO S I FOR ATIO Fault Detection U W U U The has sophisticated fault detection which can detect: Power On and Power Off sequence errors System controller command errors Power On timeout failure (with the power good timer enabled) Externally commanded faults ( pin pulled low) If any of the above faults are detected, the immediately pulls the - pins low turning off all of the power supplies. If the fault condition is detected in one of the supplies controlled by the (an internally generated fault), the pin is immediately pulled low indicating the fault condition. Clearing the Fault Condition In order to clear the fault condition within the, the following conditions must exist: All four IN pins must be below The pin must be below In the case of an externally generated fault, the pin must not be pulled down. Fault Condition Indicator If the receives a commanded fault (a cascaded or an external source pulls down on the pin) the will pull the pin low. If the has detected the fault itself (from its internal fault detection circuits) it will indicate so by raising the pin to. This internal/external fault indicator can be especially helpful while searching for the source of a fault condition when multiple s are cascaded. If a fault occurs when the pin is high, the fault status indication on the pin will remain valid until the pin goes low. Note that the pin may take a while to reach the voltage. The pin is pulled to with the same 5µA current source used for the function. The larger the timer capacitor, the longer this will take. To estimate the amount of time required for the pin to reach in a fault condition, multiply the normal timer duration by (in Volts). See Figures 7 and 8 for pin connections when two or more chips are cascaded. Sequence Errors The keeps track of power supplies that should be on during the Power On sequence and the Power Off sequence. The also monitors each IN pin after all of the power supplies have sequenced on. If a power supply (as monitored at the - pins) goes low when it should be high, a fault condition is detected. All four OUT pins are pulled low and the pin will be pulled low. The precision voltage threshold for detection of a sequence error at any of the - pins is the same as the normal threshold (~). The precision voltage comparators used in the employ a sampled technique to improve accuracy. The sample time is approximately 20µs. To improve the speed of detection for a sequence error, a second high speed comparator is used for detecting a low power supply. The voltage threshold for the high speed comparators is approximately 0.4V (V () ). Voltages sensed below this threshold when a power supply should be will cause a fault in ~1µs. System Controller Command Errors Once the receives the Power On command via the pin, the pin must remain above until the Power On sequence has completed (e.g. DE is asserted). Removing the command before the Power On sequence has completed is considered a fault condition. All of the - pins that are already high will be pulled low and the pin will be pulled low. The same is true for the Power Off sequence. If the has completed the Power On sequence and the pin goes low, the pin must remain below until the Power Off sequence has completed. Raising the pin above before the Power Off sequence has completed is considered a fault condition. Any OUTn pins that are still high will immediately be pulled low and the pin will be pulled low. 13
APPLICATIO S I FOR ATIO U W U U Power On Timeout Errors If the PGT is being used (not tied to ground) a fault condition will be detected when the PGT pin goes above ~1V. If this occurs during Power On, all of the - pins that are already high will be pulled low and the pin will be pulled low. Externally Commanded Faults If an external circuit pulls the pin low, an external fault condition is detected and all OUT pins will be pulled low. After sensing the Externally Commanded Fault, the will also pull down on the pin until the conditions for clearing the fault condition exist (see Clearing the Fault Condition). TYPICAL APPLICATIO S U Shutdown Pin Power Supply Sequencer EARLY* SYSTEM CTROLLER POWER SUPPLY 1 POWER SUPPLY 2 POWER SUPPLY 3 POWER SUPPLY 4 3.3V * EARLY MUST BE BEFORE SEQUENCING SUPPLIES 1.6V 2. DE HYS/CFG PGT 24.9k 9.31k 49.9k 2924 TA03 15.8k 49.9k V 3.01V V OFF 2.68V V 4.49V V OFF 3.99V V 1.43V V OFF 1.27V V 2.2 V OFF 2V 33.2k 11.81k 7.87k 8.45k Power On Sequence Timer Delay Longer than Power Off Sequence Timer Delay PGT DE 14 2924 TA05 POWER TIMER DELAY = 30ms POWER OFF TIMER DELAY = 15ms
TYPICAL APPLICATIO S U 2-Supply Sequencer with Delayed Sense Pin, One Channel Unused OUT + MODULE SENSE + DC/DC 3.3V Q2 Q1 D1 1M PARASITIC RESISTANCE V OUT V OUT 3.3V V 4.64V V OFF 4V V 2.98V V OFF 2.6 64.9k 33.2k SYSTEM CTROLLER PGT D1: 1N5711 Q1, Q2: IRL3714S DE HYS 49.9k 9.83k 8.55k 2924 TA01a Power-On Power-Off REMOTE SENSE ENABLE REMOTE SENSE DISABLE 2V/DIV 3.3V 2V/DIV 3.3V 1V/DIV 1V/DIV 1V/DIV 1V/DIV 25ms/DIV 2924 TA01b 25ms/DIV 2924 TA01C Information furnished by Linear Technology Corporation is believed to be accurate and reliable. However, no responsibility is assumed for its use. Linear Technology Corporation makes no representation that the interconnection of its circuits as described herein will not infringe on existing patent rights. 15
TYPICAL APPLICATIO U 12V 3-Supply Sequencer with Power Supplied by a Zener Shunt Regulator SYSTEM 12V SUPPLY 12V 1.2V V IN 1.1V, OFF 1.09V 1k µc 1 2 RESET_B 1.24k FPGA 3.3V V IN 3V, OFF 2.8V 20k 1 2 5.11k ASIC 2. V IN 2.2V, OFF 2V 20k 1 2 5.1V ZENER BZX84C1 1.5k 49.9k 2.94k 49.9k HYS/CFG DE PGT 7.68k 2924 TA04 PACKAGE DESCRIPTIO U GN Package 16-Lead Plastic SSOP (Narrow.150 Inch) (Reference LTC DWG # 05-08-1641).007.0098 (0.178 0.249).015 ±.004 (0.38 ± 0.10) 45 0 8 TYP.0532.0688 (1.35 1.75).004.0098 (0.102 0.249).189.196* (4.801 4.978) 16 15 14 13 12 11 10 9.009 (0.229) REF.045 ±.005.016.050 (0.406 1.270) NOTE: 1. CTROLLING DIMENSI: INCHES INCHES 2. DIMENSIS ARE IN (MILLIMETERS) 3. DRAWING NOT TO SCALE.008.012 (0.203 0.305) TYP.0250 (0.635) BSC *DIMENSI DOES NOT INCLUDE MOLD FLASH. MOLD FLASH SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE **DIMENSI DOES NOT INCLUDE INTERLEAD FLASH. INTERLEAD FLASH SHALL NOT EXCEED 0.010" (0.254mm) PER SIDE.229.244 (5.817 6.198) 1 2 3 4 5 6 7 8.150.157** (3.810 3.988).254 MIN.0165 ±.0015.150.165 RECOMMENDED SOLDER PAD LAYOUT GN16 (SSOP) 0204.0250 BSC RELATED PARTS PART NUMBER DESCRIPTI COMMENTS LTC2920-1/ Single/Dual Power Supply Margining Controller Symmetric/Asymmetric High and Low Voltage Margining LTC2920-2 LTC2921/LTC2922 Power Supply Tracker with Input Monitors 3 (LTC2921) or 5 (LTC2922) Remote Sense Switching LTC2923 Power Supply Tracking Controller Up to 3 Supplies LTC2925 Multiple Power Supply Tracking Controller Power Good Timer, Remote Sense Switch 16 LT/TP1204 1K PRINTED IN USA Linear Technology Corporation 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear.com LINEAR TECHNOLOGY CORPORATI 2004