ISL8702IBZ

DATASHEET ISL8700, ISL8701, ISL8702 FN9250 Rev 2.00 March 21, 2008 Adjustable Quad Sequencer The ISL8700, ISL8701, ISL8702 family of ICs provide four delay adjustable sequenced outputs while monitoring an input voltage all with a minimum of external components. Features High performance DSP, FPGA, µP and various subsystems require input power sequencing for proper functionality at initial power-up and the ISL870x provides this function while monitoring the distributed voltage for over and undervoltage compliance. • Adjustable Delay to Sequence Auto Start The ISL8700 and ISL8701 operate over the +2.5V to +24V nominal voltage range, whereas the ISL8702 operates over the +2.5V to +12V nominal voltage range. All three have a user adjustable time from UV and OV voltage compliance to sequencing start via an external capacitor when in auto start mode and adjustable time delay to subsequent ENABLE output signal via external resistors. Additionally, the ISL8702 provides an input for sequencing on and off operation (SEQ_EN) and for voltage window compliance reporting (FAULT) over the +2.5V to +12V voltage range. Easily daisy chained for more than 4 sequenced signals. Altogether, the ISL870x provides these adjustable features with a minimum of external BOM. See Figure 1 for typical implementation. • Adjustable Delay to Subsequent Enable Signal • Adjustable Distributed Voltage Monitoring • Undervoltage and Overvoltage Adjustable Delay to Auto Start Sequence • I/O Options ENABLE (ISL8700, ISL8702) and ENABLE# (ISL8701) SEQ_EN (ISL8702) • Voltage Compliance Fault Output • Pb-Free (RoHS Compliant) Applications • Power Supply Sequencing • System Timing Function 2.5V TO 24V (2.5V TO 12V FOR ISL8702) Ru ISL8700IBZ* ISL 8700IBZ -40 to +85 14 Ld SOIC M14.15 ISL8701IBZ* ISL 8701IBZ -40 to +85 14 Ld SOIC M14.15 ISL8702IBZ* ISL 8702IBZ -40 to +85 14 Ld SOIC M14.15 ISL870xEVAL1 Evaluation Platform *Add “-T” suffix for tape and reel. Please refer to TB347 for details on reel specifications. NOTE: These Intersil Pb-free plastic packaged products employ special Pb-free material sets; molding compounds/die attach materials and 100% matte tin plate PLUS ANNEAL - e3 termination finish, which is RoHS compliant and compatible with both SnPb and Pb-free soldering operations. Intersil Pb-free products are MSL classified at Pb-free peak reflow temperatures that meet or exceed the Pb-free requirements of IPC/JEDEC J STD-020. FN9250 Rev 2.00 March 21, 2008 UV ENABLE_A ENABLE_B ENABLE_C ENABLE_D OV FAULT* SEQ_EN* Ordering Information PART NUMBER PART TEMP. PACKAGE PKG. (Note) MARKING RANGE (°C) (Pb-free) DWG. # VIN Rm GND TB TC TD TIME EN DC/DC Vo1 EN DC/DC Vo2 EN DC/DC Vo3 EN DC/DC Vo4 Rl * SEQ_EN and FAULT are not available on ISL8700 and ISL8701 FIGURE 1. ISL870x IMPLEMENTATION Page 1 of 13 ISL8700, ISL8701, ISL8702 Pinouts ISL8702 (14 LD SOIC) TOP VIEW ISL8701 (14 LD SOIC) TOP VIEW ISL8700 (14 LD SOIC) TOP VIEW ENABLE_D 1 14 VIN ENABLE#_D 1 14 VIN ENABLE_D 1 14 VIN ENABLE_C 2 13 TD ENABLE#_C 2 13 TD ENABLE_C 2 13 TD ENABLE_B 3 12 TC ENABLE#_B 3 12 TC ENABLE_B 3 12 TC ENABLE_A 4 11 TB ENABLE#_A 4 11 TB ENABLE_A 4 11 TB OV 5 10 TIME OV 5 10 TIME OV 5 10 TIME UV 6 9 NC UV 6 9 NC UV 6 9 SEQ_EN GND 7 8 NC GND 7 8 NC GND 7 FN9250 Rev 2.00 March 21, 2008 8 FAULT Page 2 of 13 ISL8700, ISL8701, ISL8702 Absolute Maximum Ratings Thermal Information ISL8700, ISL8701 VIN, ENABLE(#), FAULT . . . . . . . . 27V, to -0.3V ISL8702 VIN, ENABLE(#), FAULT . . . . . . . . . . . . . . . . 14V, to -0.3V TIME, TB, TC, TD, UV, OV . . . . . . . . . . . . . . . . . . . . . +6V, to -0.3V SEQ_EN(#) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . VIN+0.3V, to -0.3V ENABLE, ENABLE # Output Current . . . . . . . . . . . . . . . . . . . 10mA Thermal Resistance (Typical, Note 1) JA (°C/W) 14 Ld SOIC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 110 Maximum Junction Temperature (Plastic Package) . . . . . . . +125°C Maximum Storage Temperature Range . . . . . . . . . .-65°C to +150°C Pb-free Reflow Profile . . . . . . . . . . . . . . . . . . . . . . . . .see link below http://www.intersil.com/pbfree/Pb-FreeReflow.asp Operating Conditions Temperature Range . . . . . . . . . . . . . . . . . . . . . . . . . .-40°C to +85°C Supply Voltage Range (Nominal). . . . . . . . . . . . . . . . . . 2.5V to 24V ISL8702 Supply Voltage Range (Nominal) . . . . . . . . . . 2.5V to 12V CAUTION: Do not operate at or near the maximum ratings listed for extended periods of time. Exposure to such conditions may adversely impact product reliability and result in failures not covered by warranty. NOTE: 1. JA is measured with the component mounted on a high effective thermal conductivity test board in free air. See Tech Brief TB379 for details. Electrical Specifications Nominal VIN = 2.5V to +24V, TA = TJ = -40°C to +85°C, Unless Otherwise Specified. ISL8702 VIN = 2.5V to +12V PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT UV AND OV INPUTS UV/OV Rising Threshold VUVRvth 1.16 1.21 1.28 V UV/OV Falling Threshold VUVFvth 1.06 1.10 1.18 V UV/OV Hysteresis VUVhys - 104 - mV IUV - 10 - nA ITIME - 2.6 - µA TIME Pin Threshold VTIME_VTH 1.9 2.0 2.25 V Time from VIN Valid to ENABLE_A tVINSEQpd SEQ_EN = high, CTIME = open - 30 - µs tVINSEQpd_10 SEQ_EN = high, CTIME = 10nF - 7.7 - ms tVINSEQpd500 SEQ_EN = high, CTIME = 500nF - 435 - ms UV or OV to simultaneous shutdown - - 1 µs UV/OV Input Current VUVRvth - VUVFvth TIME, ENABLE/ENABLE# OUTPUTS TIME Pin Charging Current Time from VIN Invalid to Shutdown tshutdown ENABLE Output Resistance REN IENABLE = 1mA - 100 -  ENABLE Output Low Vol IENABLE = 1mA - 0.1 - V ENABLE Pull-Down Current Delay to Subsequent ENABLE Turn-On/Off Ipulld ENABLE = 1V 10 15 - mA tdel_120 RTX = 120k 155 195 240 ms tdel_3 RTX = 3k 3.5 4.7 6 ms tdel_0 RTX = 0 - 0.5 - ms SEQUENCE ENABLE AND FAULT I/O VIN Valid to FAULT Low tFLTL 15 30 50 µs VIN Invalid to FAULT High tFLTH - 0.5 - µs 10 15 - mA - VIN - V FAULT Pull-down Current SEQ_EN Pull-up Voltage FAULT = 1V VSEQ SEQ_EN open SEQ_EN Low Threshold Voltage VilSEQ_EN - - 0.3 V SEQ_EN High Threshold Voltage VihSEQ_EN 1.2 - - V Delay to ENABLE_A Deasserted tSEQ_EN_ENA - 0.2 1 µs FN9250 Rev 2.00 March 21, 2008 SEQ_EN low to ENABLE_A low Page 3 of 13 ISL8700, ISL8701, ISL8702 Electrical Specifications Nominal VIN = 2.5V to +24V, TA = TJ = -40°C to +85°C, Unless Otherwise Specified. ISL8702 VIN = 2.5V to +12V (Continued) PARAMETER SYMBOL TEST CONDITIONS MIN TYP MAX UNIT BIAS IC Supply Current VIN Power On Reset IVIN_2.2V VIN = 2.2V - 191 - µA IVIN_12V VIN = 12V - 246 400 µA IVIN_24V VIN = 24V - 286 - µA VIN_POR VIN low to high - 2.08 2.5 V Pin Descriptions PIN NUMBER ISL8700 ISL8701 ISL8702 PIN NAME FUNCTION DESCRIPTION NA 1 NA ENABLE#_D Active low open drain sequenced output. Sequenced on after ENABLE#_C and first output to sequence off for the ISL8701. Tracks VIN upon bias. 1 NA 1 ENABLE_D Active high open drain sequenced output. Sequenced on after ENABLE_C and first output to sequence off for the ISL8700, ISL8702. Pulls low with VIN < 1V. NA 2 NA ENABLE#_C Active low open drain sequenced output. Sequenced on after ENABLE#_B and sequenced off after ENABLE#_D for the ISL8701. Tracks VIN upon bias. 2 NA 2 ENABLE_C Active high open drain sequenced output. Sequenced on after ENABLE_B and sequenced off after ENABLE_D for the ISL8700, ISL8702. Pulls low with VIN < 1V. NA 3 NA ENABLE#_B Active low open drain sequenced output. Sequenced on after ENABLE#_A and sequenced off after ENABLE#_C for the ISL8701. Tracks VIN upon bias. 3 NA 3 ENABLE_B Active high open drain sequenced output. Sequenced on after ENABLE_A and sequenced off after ENABLE_C for the ISL8700, ISL8702. Pulls low with VIN < 1V. NA 4 NA ENABLE#_A Active low open drain sequenced output. Sequenced on after CTIME period and sequenced off after ENABLE#_B for the ISL8701. Tracks VIN upon bias. 4 NA 4 ENABLE_A Active high open drain sequenced output. Sequenced on after CTIME period and sequenced off after ENABLE_B for the ISL8700, ISL8702. Pulls low with VIN < 1V. 5 5 5 OV The voltage on this pin must be under its 1.22V Vth or the four ENABLE outputs will be immediately pulled down. Conversely the 4 ENABLE# outputs will be released to be pulled high via external pull ups. 6 6 6 UV The voltage on this pin must be over its 1.22V Vth or the four ENABLE outputs will be immediately pulled down. Conversely the 4 ENABLE# outputs will be released to be pulled high via external pull ups. 7 7 7 GND NA NA 8 FAULT NA NA 9 SEQ_EN This pin provides a sequence on signal input with a high input. Internally pulled high to VIN. NA NA NA SEQ_EN# This pin provides a sequence on signal input with a low input. Internally pulled high to VIN. 10 10 10 TIME This pin provides a 2.6µA current output so that an adjustable VIN valid to sequencing on and off start delay period is created with a capacitor to ground. 11 11 11 TB A resistor connected from this pin to ground determines the time delay from ENABLE_A being active to ENABLE _B being active on turn-on and also going inactive on turn-off via the SEQ_IN input. 12 12 12 TC A resistor connected from this pin to ground determines the time delay from ENABLE_B being active to ENABLE _C being active on turn-on and also going inactive on turn-off via the SEQ_IN input. 13 13 13 TD A resistor connected from this pin to ground determines the time delay from ENABLE_C being active to ENABLE _D being active on turn-on and also going inactive on turn-off via the SEQ_IN input. 14 14 14 VIN IC Bias Pin Nominally 2.5V to 24V (2.5V to 12V for ISL8702). This pin requires a 1µF decoupling capacitor close to IC pin. FN9250 Rev 2.00 March 21, 2008 IC ground. The VIN voltage when not within the desired UV to OV window will cause FAULT to be released to be pulled high to a voltage equal to or less than VIN via an external resistor. Page 4 of 13 ISL8700, ISL8701, ISL8702 Functional Block Diagram VIN (2.2V MIN TO 27V MAX, 2.5V TO 12V FOR ISL8702) VIN VREF VOLTAGE REFERENCE 1.17V VREG INTERNAL VOLTAGE 3.5V REGULATOR SEQ_EN UV + eo + OV 2.0V VIN POR LOGIC - ENABLE_A ENABLE_B FAULT 30µs GND ENABLE_C VTIME_VTH PROGRAMMABLE DELAY TIMER VIN ENABLE_D 2.6µA TIME TB Functional Description The ISL870x family of ICs provides four delay adjustable sequenced outputs while monitoring a single distributed voltage in the nominal range of 2.5V to 24V for both under and overvoltage. Only when the voltage is in compliance will the ISL870x initiate the pre-programmed A-B-C-D sequence of the ENABLE (ISL8700, ISL8702) or ENABLE# (ISL8701) outputs. Although this IC has a bias range of 2.5V to 24V (12V for ISL8702) it can monitor any voltage >1.22V via the external divider if a suitable bias voltage is otherwise provided. During initial bias voltage (VIN) application, the ISL8700, ISL8702 ENABLE outputs are held low once VIN = 1V whereas the ISL8701 ENABLE# outputs follow the rising VIN. Once VIN > the VBIAS power-on reset threshold (POR) of 2.0V, VIN is constantly monitored for compliance via the input voltage resistor divider and the voltages on the UV and OV pins and reported by the FAULT output. Internally, voltage regulators generate 3.5V and 1.17V ±5% voltage rails for internal usage once VIN > POR. Once UV > 1.22V and with the SEQ_EN pin high or open, the auto sequence of the four ENABLE (ENABLE#) outputs begins as the TIME pin charges its external capacitor with a 2.6µA current source. The voltage on TIME is compared to the internal reference (VTIME_VTH) comparator input and when greater than VTIME_VTH the ISL8700, ISL8702 ENABLE_A is released to go high via an external pull-up FN9250 Rev 2.00 March 21, 2008 TC TD resistor or a pull-up in a DC/DC convertor enable input, for example. Conversely, ENABLE#_A output will be pulled low at this time on an ISL8701. The time delay generated by the external capacitor is to assure continued voltage compliance within the programmed limits, as during this time any OV or UV condition will halt the start-up process. TIME capacitor is discharged once VTIME_VTH is met. Once ENABLE_A is active (either released high on the ISL8700, ISL8702 or pulled low on the ISL8701), a counter is started and using the resistor on TB as a timing component, a delay is generated before ENABLE_B is activated. At this time, the counter is restarted using the resistor on TC as its timing component for a separate timed delay until ENABLE_C is activated. This process is repeated for the resistor on TD to complete the A-B-C-D sequencing order of the ENABLE or ENABLE# outputs. At any time during sequencing if an OV or UV event is registered, all four ENABLE outputs will immediately return to their reset state; low for ISL8700, ISL8702 and high for ISL8701. CTIME is immediately discharged after initial ramp-up thus waiting for subsequent voltage compliance to restart. Once sequencing is complete, any subsequently registered UV or OV event will trigger an immediate and simultaneous reset of all ENABLE or ENABLE# outputs. Page 5 of 13 ISL8700, ISL8701, ISL8702 On the ISL8702, enabling of on or off sequencing can also be signaled via the SEQ_EN input pin once voltage compliance is met. Initially the SEQ_EN pin should be held low and released when sequence start is desired. The on sequence of the ENABLE outputs is as previously described. The off sequence feature is only available on the variants having the SEQ_EN or the SEQ_EN# inputs, this being the ISL8702. The sequence is D off, then C off, then B off and finally A off. Once SEQ_EN (SEQ_EN#) is signaled low (high) the TIME cap is charged to 2V once again. Once this Vth is reached ENABLE_D transitions to its reset state and CTIM is discharged. A delay and subsequent sequence off is then determined by TD resistor to ENABLE_C. Likewise, a delay to ENABLE_B and then ENABLE_A turn-off is determined by TC and TB resistor values respectively. With the ISL8700, ISL8701, a quasi down sequencing of the ENABLE outputs can be achieved by loading the ENABLE pins with various value capacitors to ground. When a simultaneous output latch off is invoked, the caps will set the falling ramp of the various ENABLE outputs thus adjusting the time to Vth for various DC/DC convertors or other circuitry. Regardless of IC variant, the FAULT signal is always valid at operational voltages and can be used as justification for SEQ_EN release or even controlled with an RC timer for sequence on. Programming the Undervoltage and Overvoltage Limits When choosing resistors for the divider, remember to keep the current through the string bounded by power loss at the top end and noise immunity at the bottom end. For most applications, total divider resistance in the 10kto 1000krange is advisable with high precision resistors being used to reduce monitoring error. Although for the ISL870x two dividers of two resistors each can be employed to separately monitor the OV and UV levels for the VIN voltage which will be discussed here using a single three resistor string for monitoring the VIN voltage, referencing Figure 1. In the three resistor divider string with Ru (upper), Rm (middle) and Rl (lower), the ratios of each in combination to the other two is balanced to achieve the desired UV and OV trip levels. Although this IC has a bias range of 2.5V to 24V (12V for ISL8702), it can monitor any voltage >1.22V. The ratio of the desired overvoltage trip point to the internal reference is equal to the ratio of the two upper resistors to the lowest (ground connected) resistor. The ratio of the desired undervoltage trip point to the internal reference voltage is equal to the ratio of the uppermost (voltage connected) resistor to the lower two resistors. These assumptions are true for both rising (turn-on) or falling (shutdown) voltages. FN9250 Rev 2.00 March 21, 2008 The following is a practical example worked out. For detailed equations on how to perform this operation for a given supply requirement, please refer to the next section. 1. Determine if turn-on or shutdown limits are preferred and in this example we will determine the resistor values based on the shutdown limits. 2. Establish lower and upper trip level: 12V ±10% or 13.2V (OV) and 10.8V (UV) 3. Establish total resistor string value: 100kIr = divider current 4. (Rm + Rl) x Ir = 1.1V @ UV and Rl x Ir = 1.2V @ OV 5. Rm + Rl = 1.1V/Ir @ UV Rm + Rl = 1.1V/(10.8V/100k) = 10.370k 6. Rl = 1.2V/Ir @ OV Rl = 1.2V/(13.2V/100k) = 9.242k 7. Rm = 10.370k - 9.242k = 1.128k 8. Ru = 100k- 10.370k= 89.630k 9. Choose standard value resistors that most closely approximate these ideal values. Choosing a different total divider resistance value may yield a more ideal ratio with available resistors values. In our example with the closest standard values of Ru = 90.9kRm = 1.13k and Rl = 9.31kthe nominal UV falling and OV rising will be at 10.9V and 13.3V respectively. An Advanced Tutorial on Setting UV and OV Levels This section discusses in additional detail the nuances of setting the UV and OV levels, providing more insight into the ISL870x than the earlier text. The following equation set can alternatively be used to work out ideal values for a 3 resistor divider string of Ru, Rm and Rl. These equations assume that VREF is the center point between VUVRvth and VUVFvth (i.e. (VUVRvth + VUVFvth)/2 = 1.17V), Iload is the load current in the resistor string (i.e. VIN /(Ru + Rm + Rl)), VIN is the nominal input voltage and Vtol is the acceptable voltage tolerance, such that the UV and OV thresholds are centered at VIN ± Vtol. The actual acceptable voltage window will also be affected by the hysteresis at the UV and OV pins. This hysteresis is amplified by the resistor string such that the hysteresis at the top of the string is calculated in Equation 1: Vhys = V UVhys  V OUT  V REF (EQ. 1) This means that the VIN ± Vtol thresholds will exhibit hysteresis resulting in thresholds of VIN + Vtol ± Vhys/2 and VIN - Vtol ± Vhys/2. There is a window between the VIN rising UV threshold and the VIN falling OV threshold where the input level is guaranteed not to be detected as a fault. This window exists between the limits VIN ± (Vtol - Vhys/2). There is an extension of this window in each direction up to VIN ± (Vtol + Vhys/2), where the voltage may or may not be Page 6 of 13 ISL8700, ISL8701, ISL8702 detected as a fault, depending on the direction from which it is approached. These two equations may be used to determine the required value of Vtol for a given system. For example, if VIN is 12V, Vhys = (0.1 x 12)/1.17 = 1.03V. If VIN must remain within 12V ± 1.5V, Vtol = 1.5 - 1.03/2 = 0.99V. This will give a window of 12 ±0.48V where the system is guaranteed not to be in fault and a limit of 12 ±1.5V beyond which the system is guaranteed to be in fault. It is wise to check both these voltages for if the latter is made too tight, the former will cease to exist. This point comes when Vtol < Vhys/2 and results from the fact that the acceptable window for the OV pin no longer aligns with the acceptable window for the UV pin. In this case, the application will have to be changed such that UV and OV are provided separate resistor strings. In this case the UV and OV thresholds can be individually controlled by adjusting the relevant divider. The previous example will give voltage thresholds: with VIN rising UVr = V IN – V tol + V hys  2 = 11.5Vand OVr = V IN + V tol + V hys  2 = 13.5V (EQ. 2) with VIN falling OVf = V IN + V tol – V hys  2 = 12.5Vand (EQ. 3) UVf = V IN – V tol – V hys  2 = 10.5V So with a single three resistor string, the resistor values can be calculated using Equation 4: R I =  V REF  I load   1 – V tol  V IN  R m = 2  V REF  V tol    V IN  I load  (EQ. 4) R u =  1  I load    V IN – V REF   1 + V tol  V IN  Programming the ENABLE Output Delays The delay timing between the four sequenced ENABLE outputs are programmed with four external passive components. The delay from a valid VIN (ISL8700 and ISL8701) to ENABLE_A and SEQ_EN being valid (ISL8702) to ENABLE_A is determined by the value of the capacitor on the TIME pin to GND. The external TIME pin capacitor is charged with a 2.6µA current source. Once the voltage on TIME is charged up to the internal reference voltage, (VTIME_VTH) the ENABLE_A output is released out of its reset state. The capacitor value for a desired delay (±10%) to ENABLE_A once VIN and SEQ_EN where applicable has been satisfied is determined by using Equation 5: C TIME = t VINSEQpd  770k (EQ. 5) Once ENABLE_A reaches VTIME_VTH, the TIME pin is pulled low in preparation for a sequenced off signal via SEQ_EN. At this time, the sequencing of the subsequent outputs is started. ENABLE_B is released out of reset after a programmable time, then ENABLE_C, then ENABLE _D, all with their own programmed delay times. The subsequent delay times are programmed with a single external resistor for each ENABLE output providing maximum flexibility to the designer through the choice of the resistor value connected from TB, TC and TD pins to GND. The resistor values determine the charge and discharge rate of an internal capacitor comprising an RC time constant for an oscillator whose output is fed into a counter generating the timing delay to ENABLE output sequencing. The RTX value for a given delay time is defined as Equation 6: t del R TX = --------------------1667nF (EQ. 6) For the above example with Vtol = 0.99V, assuming a 100µA Iload at VIN = 12V: Rl = 10.7k Rm = 1.9k Ru = 107.3k FN9250 Rev 2.00 March 21, 2008 Page 7 of 13 ISL8700, ISL8701, ISL8702 FAULT SEQ_EN TIME A ENABLE OUTPUTS B C D D C B A FIGURE 2. ISL8702 OPERATIONAL DIAGRAM OVERVOLTAGE LIMIT UV LEVEL VMON > OV LEVEL FAULT OUTPUT FIGURE 6. VMONITOR RISING TO FAULT FN9250 Rev 2.00 March 21, 2008 VMON > OV LEVEL VMON > UV LEVEL FAULT OUTPUT FIGURE 7. VMONITOR FALLING TO FAULT Page 9 of 13 ISL8700, ISL8701, ISL8702 RTB = 3k RTB = 3k DELAY = 5ms DELAY = 5ms RTC = 51k RTD = 120k DELAY = 196ms DELAY = 86ms RTC = 51k DELAY = 86ms RTD = 120k DELAY = 196ms FIGURE 8. ENABLE_X TO ENABLE_X ENABLING FIGURE 9. ENABLE_X TO ENABLE_X DISABLING VIN RISING CTIME = 10nF DELAY = 8.5ms ENABLE OUTPUTS TRACKS VIN TO < 0.8V 1V/DIV FIGURE 10. VIN/SEQ_EN VALID TO ENABLE_A 10ms/DIV FIGURE 11. ENABLE AS VIN RISES VMONITOR OV SEQ_EN ENABLE_A VMONITOR UV TIME 0.5V/DIV FAULT = LOW 8µs/DIV FIGURE 12. SEQ_EN TO ENABLE_A FN9250 Rev 2.00 March 21, 2008 FIGURE 13. OV AND UV TRANSIENT IMMUNITY Page 10 of 13 ISL8700, ISL8701, ISL8702 Application Concerns and Recommendations When designing the ISL8700 family of products into applications with low supply voltages such as 3.3V, additional filtering to help reduce system noise on the voltage supply input is necessary to ensure proper voltage sequencing operation. It is important that the user-programmed UV threshold is set sufficiently above (i.e. >200mV) the ISL8700 IC’s internal POR level, VIN_POR, over the entire operating temperature range. Best design practices include proper decoupling on the supply input (i.e. at least 1µF) as well as an RC filter that can adequately suppress noise on the supply in the user’s application, whereby the resistor should be kept < 13 to reduce voltage loss to the already low biased VIN pin. Coupling from the ENABLE_X pins to the sensitive UV and OV pins can cause false OV/UV events to be detected. This is most relevant for ISL8700, ISL8702 parts due to the ENABLE_A and OV pins being adjacent. This coupling can be reduced by adding a ground trace between UV and the ENABLE/FAULT signals, as shown in Figure 14. The PCB traces on OV and UV should be kept as small as practical and the ENABLE_X and FAULT traces should ideally not be routed under/over the OV/UV traces on different PCB layers unless there is a ground or power plane in between. Other methods that can be used to eliminate this issue are by reducing the value of the resistors in the network connected to UV and OV (R2, R3, R5 in Figure 15) or by adding small decoupling capacitors to OV and UV (C2 and C7 in Figure 15). Both these methods act to reduce the AC impedance at the nodes, although the latter method acts to filter the signals, which will also cause an increase in the time that a UV/OV fault takes to be detected. PIN 4 GND GND PIN 5 FIGURE 14. LAYOUT DETAIL OF GND BETWEEN PINS 4 AND 5 When the ISL870x is implemented on a hot swappable card that is plugged into an always powered passive back plane, an RC filter is required on the VIN pin to prevent a high dv/dt transient. With the already existing 1µF decoupling capacitor, the addition of a small series R (50µs is all that is necessary. Only the ISL8702 has a VIN limitation of 14V maximum. FN9250 Rev 2.00 March 21, 2008 Page 11 of 13 ISL8700, ISL8701, ISL8702 . PULL-UP RESISTORS TIMING COMPONENTS UV/OV SET RESISTORS FIGURE 15. ISL870xEVAL1 PHOTOGRAPH AND SCHEMATIC OF LEFT CHANNEL TABLE 1. ISL870xEVAL1 LEFT CHANNEL COMPONENT LISTING COMPONENT DESIGNATOR COMPONENT FUNCTION COMPONENT DESCRIPTION U1 ISL8702, Quad Under/Overvoltage Sequencer Intersil, ISL8702, Quad Undervoltage, Overvoltage Sequencer R3 UV Resistor for Divider String 1.1k 1%, 0603 R2 VMONITOR Resistor for Divider String 88.7k 1%, 0603 R5 OV Resistor for Divider String 9.1k 1%, 0603 C1 CTIME Sets Delay from Sequence Start to First ENABLE 0.01µF, 0603 R1 RTD Sets Delay from Third to Fourth ENABLE 120k 1%, 0603 R9 RTB Sets Delay from First to Second ENABLE 3.01k 1%, 0603 R7 RTC Sets Delay from Second to Third ENABLE 51k 1%, 0603 ENABLE_X(#) and FAULT Pull-up Resistors 4k10%, 0402 Decoupling Capacitor 1µF, 0603 R4, R6, R8, R10, R11 C3 FN9250 Rev 2.00 March 21, 2008 Page 12 of 13 ISL8700, ISL8701, ISL8702 Small Outline Plastic Packages (SOIC) M14.15 (JEDEC MS-012-AB ISSUE C) N INDEX AREA H 0.25(0.010) M 14 LEAD NARROW BODY SMALL OUTLINE PLASTIC PACKAGE B M E INCHES -B- 1 2 3 L SEATING PLANE -A- h x 45o A D -C- e C 0.10(0.004) C A M SYMBOL MIN MAX MIN MAX NOTES A 0.0532 0.0688 1.35 1.75 - A1 0.0040 0.0098 0.10 0.25 - B 0.013 0.020 0.33 0.51 9 C 0.0075 0.0098 0.19 0.25 - D 0.3367 0.3444 8.55 8.75 3 E 0.1497 0.1574 3.80 4.00 4 e A1 B 0.25(0.010) M  B S 0.050 BSC 1. Symbols are defined in the “MO Series Symbol List” in Section 2.2 of Publication Number 95. 1.27 BSC - H 0.2284 0.2440 5.80 6.20 - h 0.0099 0.0196 0.25 0.50 5 L 0.016 0.050 0.40 1.27 6 N NOTES: MILLIMETERS  14 0o 14 8o 0o 7 8o Rev. 0 12/93 2. Dimensioning and tolerancing per ANSI Y14.5M-1982. 3. Dimension “D” does not include mold flash, protrusions or gate burrs. Mold flash, protrusion and gate burrs shall not exceed 0.15mm (0.006 inch) per side. 4. Dimension “E” does not include interlead flash or protrusions. Interlead flash and protrusions shall not exceed 0.25mm (0.010 inch) per side. 5. The chamfer on the body is optional. If it is not present, a visual index feature must be located within the crosshatched area. 6. “L” is the length of terminal for soldering to a substrate. 7. “N” is the number of terminal positions. 8. Terminal numbers are shown for reference only. 9. The lead width “B”, as measured 0.36mm (0.014 inch) or greater above the seating plane, shall not exceed a maximum value of 0.61mm (0.024 inch). 10. Controlling dimension: MILLIMETER. Converted inch dimensions are not necessarily exact. © Copyright Intersil Americas LLC 2006-2008. All Rights Reserved. All trademarks and registered trademarks are the property of their respective owners. For additional products, see www.intersil.com/en/products.html Intersil products are manufactured, assembled and tested utilizing ISO9001 quality systems as noted in the quality certifications found at www.intersil.com/en/support/qualandreliability.html Intersil products are sold by description only. Intersil may modify the circuit design and/or specifications of products at any time without notice, provided that such modification does not, in Intersil's sole judgment, affect the form, fit or function of the product. Accordingly, the reader is cautioned to verify that datasheets are current before placing orders. Information furnished by Intersil is believed to be accurate and reliable. However, no responsibility is assumed by Intersil or its subsidiaries for its use; nor for any infringements of patents or other rights of third parties which may result from its use. No license is granted by implication or otherwise under any patent or patent rights of Intersil or its subsidiaries. For information regarding Intersil Corporation and its products, see www.intersil.com FN9250 Rev 2.00 March 21, 2008 Page 13 of 13