SC1437 Precision Voltage Detector With Programmable Trigger Voltage & Timer Delay POWER MANAGEMENT Description Features Low quiescent current, less than 10µA typical Input voltage range 1.8V to 6.8V Adjustable or preset voltage trip point Selectable timer delays of 0, 40 and 80ms without use of external resistor ! SOT-23 5 lead package ! Accuracy is 2% over specified temperature range ! 30V maximum rating ! ! ! ! The SC1437 is a battery over voltage detection circuit with driver for external MOSFET. The trip point is adjustable with an external resistor divider connected to the SENSE pin. The trip point is preset to a nominal trip voltage of 4.2V if no external divider is used. Other internal trip voltages of 4.5V and 4.7V are available, specified by different part numbers. An internal delay, with two selectable times or bypass, is on-board to suppress accidental over voltage conditions due to glitches on the battery supply voltage, V+. The delay is externally adjustable by pulling the SEL pin high, low, or left floating. During an actual over voltage condition, the internal driver will pull the over voltage pin (OV) down to the voltage present at the V- pin. This insures the external N-Channel MOSFET will be completely off during an over voltage condition. Supply current during the monitoring mode of operation is approximately 10µA. If an over voltage condition is detected, supply currents increase when the timer is started. A voltage comparator will engage at voltages greater than 6.8V, which bypasses the timer and open circuits the battery by turning off the external MOSFET. This important function protects the battery during the timer delay in the event of a charger failure. There are three functional options available. With the B option the OV pin is active low. With the L option the OV pin is active high. With the H option the OV pin is open drain, active high. All options are available in a 5 lead SOT-23 package. Applications ! ! ! ! ! ! Battery packs Portable electronics Lithium Ion protection circuits Programmable Fuse Power Monitoring CPU Reset Circuits Typical Application Circuit + R1 100 100 1 4 BATTERY 3 R2 SEL V+ 5 SENSE OV V- 2 SC1437 0.1uF 0.1uF VTRIP = 2.1(1+R2/R1) 0.476 < (R2/R1) < 2 Revision 01/10/2001 1 www.semtech.com SC1437 POWER MANAGEMENT Absolute Maximum Rating Par ame te r Symbo l Maximum Units V+ Sup p ly Voltage to (V-) V+ -0.3 to 30 V Over Voltage Outp ut to (V-) OV -0.3 to 8 V Select to (V-) SEL -0.3 to 7 V Sense to (V-) SEN SE -0.3 to 7 V Thermal Resistance Junction to Ambient θJA 256 °C/W Op erating Ambient Temp erature Range TA -40 to +85 °C Op erating Junction Temp erature Range TJ -40 to +125 °C Storage Temp erature Range TSTG -65 to +150 °C Lead Temp erature (Soldering) 10 sec. T LE A D 300 °C ESD Rating (Human Body Model) ESD 2 kV Electrical Characteristics Unless specified, TA = 25 OC, V+ = 1.8V to 6.3V. Values in bold apply over the full operating temperature range. Par ame te r Symbo l Te st Co nditio ns MI N Inp ut Sup p ly Voltage V+ Battery inp ut voltage 1 .8 Inp ut Sup p ly Current I+ With internal divider; V+ = 4.7V V T R IP SEN SE = V-, 4.2V Op tion Over Voltage Threshold with Resp ect to V- MAX Units 6.3 V 10 14 µA 4.12 4.2 4.28 V SEN SE = V-, 4.5V Op tion 4.41 4.5 4.59 V SEN SE = V-, 4.7V Op tion 4.61 4.7 4.79 V External Divider, VSENSE + 2.1V, VSENSE = 1V to 4.2V Inp ut Bias Current OV Threshold Hystersis OV Drive Current Delay 2 % IBSEN Sense Pin 1 µA IBSEL Select Pin 1 µA hyst SEN SE = V-, 4.2V Op tion 420 SEN SE = V-, 4.5V Op tion 450 SEN SE = V-, 4.7V Op tion 470 SEN SE = resistor divider VTRIP* 0.1 B Version 150 uA H & L Version; R = 100K, V+ = 4.2V 42 uA With SEL = V+ 0 ms OVDRV tdelay mV With SEL = V- 24 40 56 With SEL = no connect 48 80 112 Clamp Voltage VCLMP Step Voltage = 3V to 15V Turn Off Time toff Turn off time of external FET with gate cap = 1nF Turn-Off Time toffbpt 6.8V Byp ass Timer Comp arator 2000 Semtech Corp. T YP 2 6.8 V 50 50 µsec µsec www.semtech.com SC1437 POWER MANAGEMENT Ordering Information Pin Configuration Top View SEL 1 V- 2 OV 3 5 V+ DEVICE(1) PACKAGE SC1437ISK-BXXTR SOT-23-5L SC1437ISK-HXXTR SOT-23-5L SC1437ISK-LXXTR SOT-23-5L Notes: (1) Where XX = 42 (4.2V), 45 (4.5V), 47 (4.7V) Only available in tape and reel packaging. A reel contains 3,000 devices. 4 SENSE SOT-23-5L Marking Information Top Mark Bottom Mark 7B45 yyww 7 = SC1437 Device Output Option: B = Output active low L = Output active high H = Output active high, with open drain Voltage Option: 42 = 4.2V; 45 = 4.5V; 47 = 4.7V yy = two-digit year of manufacture ww = two-digit week of manufacture Pin Descriptions Pin # Pin Name 1 SEL 2 V- N egative terminal of charger. 3 OV Over-voltage outp ut. Active low for version B. Active high for versions H & L. 4 5 2000 Semtech Corp. SEN SE V+ Pin Function Inp ut for timer delay selection (V+, gnd or no connect). Voltage divider inp ut for adjusting over voltage trip p oint. Tie to V- for voltage monitor configuration. Inp ut sup p ly p in. 3 www.semtech.com SC1437 POWER MANAGEMENT Block Diagram V+ V+ V+ COMPARATOR 6.8V CLAMP 4.2V* MUX V+ V+ DELAY TIMER DRIVER OV t SENSE SEL V- * Based on version selected 4.2V, 4.5V, 4.7V t B option: Output active low L option: Output active high H option: Output active high, open drain 2000 Semtech Corp. 4 www.semtech.com SC1437 POWER MANAGEMENT Applications Information allows the trip delay to be set to 0S, 40mS or 80mS by application of a jumper JP2, JP3 or leaving the jumper off, respectively. Configuration of timing delays are shown in Table 1. Once the trip delay is set to the required value the SC1437 will monitor the charger voltage. If the charger voltage equals or exceeds 5.5V the OV pin will transition from high to low (Version B) turning Q1 off, thereby breaking the circuit and protecting the battery from overvoltage. Figure 3 shows the trip delay of 80mS, while Figure 4 shows the trip delay set to 40mS and Figure 5 shows no delay set. The SC1437 can be used as a battery over voltage detection circuit with driver for an external MOSFET. In this configuration the SC1437 is capable of protecting the battery if the charger circuit fails. Because of its low cost, the SC1437 is an excellent choice in cases when primary discharge protection is not required. The part is an excellent choice for secondary over voltage protection where the battery has primary fault and discharge protection, but could benefit by adding another line of defense against charger failure. The SC1437 comes in three voltage trip options and three function options. The voltage options are 4.2V, 4.5V or 4.7V. In addition, the trip voltage levels can be adjusted with an external resistive divider. FIGURE 1 VSENSE+ R4 100 The SC1437 also has three separate functional options that affect the OV pin action: With the B option, the OV pin is active low and is used to drive an N-Channel MOSFET. With the H option, the OV pin is active high with open drain to drive a P-Channel MOSFET. Finally, the L option is active high and it's output is 5V logic high for specific use as a voltage detector flag. 1 2 V+ N O DELAY V- 40mS OPEN 80mS 2000 Semtech Corp. V+ R3 100 R1 C1 0.1uF R2 5 VOV SENSE 4 SC1437 VSENSE- VOLTAGE DETECTOR: TRIP DELAY = 0 VTRIP = 2.1(1+R2/R1) 0.476 < (R2/R1) < 2 When using the program resistors R1 & R2, Figure 2, to set an alternate trip voltage, be sure these resistors are placed across the battery on the drain side of the MOSFET. This will eliminate any voltage drop errors caused by the MOSFET on resistance. Figure 6 and Figure 7 shows the normalized trip voltage variation with respect to temperature. Note that in all cases the trip voltage remains within its 2% specified range. This is true for both the internal trip voltage and externally set trip voltage, however when using an external resistor divider, the tolerance and temperature coefficient of the resistors will add to the overall device error. Choice of the resistor tolerance and temperature coefficient will depend on your error budget. We also recommend using high value resistors to limit battery current drain. Values between 100K and 1M should suffice without introducing excessive noise into the IC. CHAR GER O VER V OL TA GE PR OTECTION CHARGER OVER VERV OLT PRO The SC1437 configuration for secondary overvoltage protection is shown in Figure 2. This is the Evaluation Board schematic. The Evaluation Board is set up to work with either internal trip voltage or external trip voltage via R1 and R2. It also can set the trip delay to all three values through jumper selection of JP2 and JP3. With CHARGER+ and CHARGER- input applied, the charger voltage will be filtered by R3 and C1. The filtered voltage will then be sensed by the V+ input. In this case the trip voltage can be set to a value other than the internal setting of 4.2V. This is done by using the on-board external resistor divider and removing JP1 shunt jumper that will allow the resistors R1 and R2 to program a trip voltage of 5.75V. The Evaluation Board also SEL C2 0.1uF TABLE 1 DELAY 3 VTRIP Any part can be configured as a voltage detector as shown in Figure 1. A programmable trip delay can be set as indicated by Table 1. In Figure 1, the trip voltage is set externally by R1 & R2. while the trip delay is set to 0 seconds plus any propagation delay of the SC1437 to allow the MOSFET to turn off, specified by parameter toff. SEL CONNECTION U1 CHOOSING THE EXTERNAL MOSFET The external switch must be a logic level MOSFET. Most logic level MOSFETs have threshold voltages in the 1V range and can handle a gate to source voltage (VGS) of 12V which is well above the clamp voltage of the SC1437. In addition, the selection should be able to handle the charging current of the battery over all temperature ranges. Whether to use a P-Channel or N-Channel MOSFET depends upon the option chosen. The B option requires the use of a N-Channel MOSFET while the H option uses a P-Channel MOSFET. 5 www.semtech.com SC1437 POWER MANAGEMENT Applications Information Continued NO JUMPER = 80ms DELAY VBAT+ 1 1 JP3 0 DELAY 1 2 R1 576K JP2 40ms DELAY 1 2 CHARGER+ R3 100 R4 100 U2 1 4 3 VTRIP 1 SEL V+ SENSE V- 5 2 OV SC1437 1 C1 0.1uF R2 1M C2 0.1uF 4 2 JP1 JUMPER IN = INTERNAL VTRIP SELECT JUMPER OUT = ADJUSTABLE VTRIP SELECT VBAT- 1 5 6 7 8 1 2 3 1 CHARGER- Q1 IRF7805 FIGURE 2 FIGURE 4: TTrip rip dela o 40mS, JP2 Shor delayy Se Sett tto Shortted. FIGURE 3: TTrip rip Dela o 80mS, JP3 & JP2 Open. Delayy se sett tto Top Trace: Charger Voltage, 5V/div Top Trace: Charger Voltage, 5V/div Bottom Trace: VTRIP, 5V/div Bottom Trace: VTRIP, 5V/div Timebase: 20ms/div Timebase: 20ms/div 2000 Semtech Corp. 6 www.semtech.com SC1437 POWER MANAGEMENT Applications Information Continued FIGURE 6: Int ernal TTrip rip V oltage (4.7V) De viation Internal Voltage Deviation perature. Plo tt ed A gainst TTem em Plott tted Against emperature. FIGURE 5: TTrip rip dela o 0mS, JP3 Shor delayy Se Sett tto Shortted. INTERNAL TRIP VOLTAGE DEVIATION OVER TEMPERATURE 0.4 DEVIATION (%) 0.2 0 -0.2 4.7V Internal -0.4 -0.6 -0.8 -1 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (Degrees C) Top Trace: Charger Voltage, 5V/div Bottom Trace: VTRIP, 5V/div Timebase: 20ms/div FIGURE 7 ernal TTrip rip V oltage (4.2V) De viation 7:: Int Internal Voltage Deviation Plo tt ed A gainst TTem em perature. Plott tted Against emperature. INTERNAL TRIP VOLTAGE DEVIATION OVER TEMPERATURE 0.2 DEVIATION (%) 0.1 0 -0.1 4.2V Internal -0.2 -0.3 -0.4 -0.5 -0.6 -40 -20 0 20 40 60 80 100 120 TEMPERATURE (Degrees C) 2000 Semtech Corp. 7 www.semtech.com SC1437 POWER MANAGEMENT Outline Drawing - SOT23-5 Land Pattern - SOT23-5 Contact Information Semtech Corporation Power Management Products Division 652 Mitchell Rd., Newbury Park, CA 91320 Phone: (805)498-2111 FAX (805)498-3804 2000 Semtech Corp. 8 www.semtech.com