Automatic_power_off_switch

Published:2009/7/24 22:09:00 Author:Jessie

Figure 6-42 shows a MAX931 comparator connected as a timed, automatic power-off circuit for a 40-mA supply. The comparator output is the supply output. With a 10-mA load, the circuit provides a voltage of (VBATT-0.12 V), but it draws only 3.5 μA of quiescent current. Using the values shown, the three-resistor voltage divider programs the maximum ±50 mV of hysteresis and sets the IN- voltage at 100 mV. This gives an IN+ trip threshold of about 50 mV for the IN+ falling. The RC time constant determines the maximum power-on time of the OUT pin (8) before power-down occurs. This period (in seconds) can be approximated by: R×C×4.6. For example: 2 M×10 μF×4.6=92 (seconds). MAXIM NEW RELEASES DATA BOOK, 1995, P, 3-57.   (View)

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AUTOMATIC_TURN_OFF_FOR_TV_SET

Published:2009/6/29 3:51:00 Author:May

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Four_cell_NiCad_power_management

Published:2009/7/24 22:47:00 Author:Jessie

Figure 8-56 shows one channel of an LTC1156 used to regulate the output of a four-cell NiCad battery pack to power a notebook or palmtop computer. Figure 8-57 shows typical four-cell NiCad discharge charaqteristics. As long as the input voltage to the regulator is sufficient to produce 5 V at the output, the regulator limits at 5 V. When the battery-pack voltage drops below 5 V, the MOSFET is fully enhanced, and acts as a direct connection between the battery and the computer circuits. A battery-voltage monitor in the microprocessor decides when the battery voltage drops below 4.6 V, and housekeeping is performed (data storage, etc.) before the batteries are completely discharged. The other three channels of the LTC 1156 act as switches (under microprocessor control) to power the remaining sections of the computer. The number of switches can be increased by adding more LTC1155 or LTC1156 circuits as needed. LINEAR TECHNOLOGY, APPLICATION NOTE 53, P. 11.   (View)

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Simple_line_transceiver

Published:2009/7/24 22:15:00 Author:Jessie

Figure 6-45 shows a MAX941 comparator connected as a simple line transceiver. The output is a clean square-wave signal at the input frequency. The output amplitude is equal to V+. See Fig. 6-46 for pin configurations. MAXIM NEW RELEASES DATA BOOK, 1995, P. 3-61, 3-69.   (View)

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Replacing_a_9_V_battery_with_two_AA_cells

Published:2009/7/24 23:12:00 Author:Jessie

Figure 8-75 shows an LT1120 linear regulator used with a 9-V battery to provide a 5-V, 30-mA output. Figure 8-76 shows an LT1173-5 switching regulator used with a 9-V battery to provide the same output. Figure 8-77 shows the same LT1173-5 used with two AA cells to provide the same output (step-up). Figure 8-78 shows efficiency for the step-down circuits. Figure 8-79 shows efficiency for the step-up (two-AA cell) circuit. The battery life for the three circuits is shown in Figs. 8-80, 8-81, and 8-82, respectively. A study of these curves shows that efficiency remains higher, and battery life is longer, with the two AA cells, for the same voltage and current output. LINEAR TECHNOLOGY, DESIGN NOTE 63, P. 1, 2.   (View)

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Alkaline_battery_switching_regulator

Published:2009/7/24 23:08:00 Author:Jessie

Figure 8-71 shows an LT1270 connected to provide a 6-V, 1-A output using three or four alkaline-battery cells (instead of NiCads). The output voltage can be changed by the selection of resistors R1 and R2, using the VOUT equation (as is the case with most switching regulators). Figure 8-72 shows alkaline-battery-life characteristics for a 6-W load. Figure 8-73 shows alkaline-battery-discharge characteristics for the same 6-W load. Figure 8-74 shows the efficiency for various alkaline-battery voltages. LINEAR TECHNOLOGY, DESIGN NOTE 41, P. 2.   (View)

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Electronic hypnotic device 2

Published:2011/8/1 2:25:00 Author:Ecco | Keyword: Electronic , hypnotic device

The electronic hypnotic device decribed in the example cangenerate simulated sound of dripping water, but also issue a low-frequency synchronized flashing signal, it is easy to reduce the tension, and the users will quickly go to sleep by listening to dripping water sound or watching flashing LED watch (LED), . The device can also be used as a stutter appliance. The working principle. The electronic circuit is composed of the oscillator circuit and LED drive circuit and audio circuit, andit is shownas Figure 9-139. Oscillator circuit consists of transistors Vl, V2 and related peripheral components. LED driver circuit consists of the transistor V3 and LED VLl-VL4. Audio circuit consists of transistor V4, coupling capacitor C2, and speaker BL, volume potentiometer RW. Turning the power switch S, the oscillator circuit oscillates, the emitter of V2 outputs oscillation signal. The oscillation signal is amplified by V3 to drive VLl-VL4 shining; another path is amplified by V4 to drive speaker BL toissue the sound of dripping water. Adjusting potentiometer RP2, RPl can change the oscillator frequency, thus changing the speed of sound dripping and LED flash frequency.   (View)

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5_V_from_two_to_three_cells_low_cost_micronpower

Published:2009/7/24 23:26:00 Author:Jessie

Figure 8-92 shovgs a MAX630 connected to provide a low-cost, micropower 5-V output, with a 1.6-V to 5-V input range. Figure 8-93 shows the efficiency curve. The quiescent current is 160 μA, with a start-up of 2 V, a maximum load current of 5 mA, and a shutdown current of 1 μA. This current is most useful in micropower applications where cost, not efficiency, is the main concern. (Efficiency can be improved by substituting a Schottky rectifier for the 1N4148, and a low-resistance inductor for L1, at the expense of higher cost.) The circuit is boot-strapped (+Vs connected to the +5-V output). In those applications where minimum start-up voltage is essential, connect the +Vs pin directly to the input. Unfortunately, removing the boot-strap connection is done at the expense of low-voltage load-current capability. MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994, P. 14.   (View)

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5_V_from_two_to_thre_cells_with_low_noise

Published:2009/7/24 23:24:00 Author:Jessie

Figure 8－90 shows a MAX751 connected to provide a 5-V output. with a 2-V to 5-V input range, but with low nolse. This circuit provides a fixed－frequency PWMalternative to the pulse-skipping control scheme usually found in low-voltageswitching-regulator ICs. (The noise generated by switching regulators is a major problem in many portable products such as cellular phones and medicalinstruments,) The trade-offs for low-noise operation are increased quiescent supply current and lower efficiency for light loads．The quiescent current with a VIN of 3 V is 1.2 mA, with a maximum load current of 100 mA (with VIN＝2.7 V). The circuit has a shutdown current of 30 μA and a fixed oscillator frequency of 170kHz，The no-load start-up is 1.2 V． Figure 8-91 shows the efficiency curves. MAXIMBATTERY MANAGEMENT CIRCUIT COLLECTION 1994 P. 13．   (View)

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Electronic hypnotic device 1

Published:2011/8/1 2:50:00 Author:Ecco | Keyword: Electronic , hypnotic device

This example describes the electronic hypnotic device made by discrete electronic components , which will issue the simulated dripping water sound of tick, tick, tick when working. If insomnia intently listens to this sound of water, then he will quickly fall asleep. The working principle.The electronic circuit is composed of the oscillator circuit and timer circuit, and it is shown as Figure 9-138. Oscillator is a relaxation oscillator composed of single-junction transistor VU and resistors R2, capacitor C2 , which outputs the narrow pulse signal with width in 1.2ms, interval in 1.4s, it emits the dropping sound by HA. Timer circuit consists of transistors Vl, V2, and starting button Sl, termination button S2 etc. It is used to control the oscillator work. Pressing the Sl, capacitor Cl is fully charged at the moment, V2 is on as the base being positively biased, so that Vl is also conducting, +9 V voltage is added to the oscillator Vl (c, e pole), the oscillator makes oscillation. About lh, Cl end the discharging (via resistor Rl, and V2, b, e node discharge), V2 and V1 are off, the oscillator stops. In the oscillator working period, If you click S2, then the Cl will discharge rapidly through the S2, so that V2, V1 are closing, the oscillator stops.   (View)

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5_V_from_four_cells_switchabie_step_up_step_down

Published:2009/7/24 23:41:00 Author:Jessie

Figure 8-104 shows a MAX639 connected to provide a 5-V output from four cells，This circuit switches from step-down to step-up mode as the battery output fallsbelow 5 V The circuit operates over an input-voltage range of 3 V to 6.5 V. with aquiescent current (VIN＝5.5 V) of 50 μA, and 110 μA for a VIN of 4.5 V The maximum load current is 200 mA with a VIN of 3.75 V Battery life is 17.2 hours(using four alkaline AA cells with 100-mA load)．Figure 8-105 shows the efficiencycurves．MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994. P. 24.   (View)

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5_V_from_four_cells_inverter_or_flyback

Published:2009/7/24 23:39:00 Author:Jessie

Figure 8-102 shows a MAX739 connected to provide a 5-V output from four cells．This circuit uses the MAX739 as an inverter with a battery-referenced output．Theinput voltage range IS 3.8 V to 11 V with a no-load startup of 4 V maximum. Quiescent current (VIN＝5 V）IS 1.8 mA with a maximum load current of 200 mA．Shutdown current is 1 μA, and battery life is 13.5 hours (using four alkaline AAcells, vith a 100-mA load). Figure 8-103 shows the efficiency curves. MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994 P.23.   (View)

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5_V_from_four_cells_preregulation

Published:2009/7/24 23:37:00 Author:Jessie

Figure 8-100 shows a MAX756 connected to provide a 5-V output from four cells. This circuit uses a diode and a PFET (in parallel) as a pre-regulator for the MAX756 boost regulator. The input voltage range is 2 V to 6.2 V, with a no-load start-up of 1.5 V, The quiescent current (VIN = 5 V) is 70 μA, with a maximum load current of 400 mA. The shutdown current is 55 μA, and battery life is 15.5 hours (using four alkaline AA cells with a 100-mA load). Figure 8-101 shows the efficiency curves, MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994, P. 22.   (View)

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3_V_33_V_from_three_cells_with_linear_regulation

Published:2009/7/24 23:28:00 Author:Jessie

Figure 8-94 shows a MAX872 voltage reference and an ICL7611 micropower op amp connected to form a linear regulator for a 3-V/3.3-V supply. This circuit is particularly effective with NiCad and NiMH batteries. The end of life for such cells is about 1 V, so a linear regulator (with very low dropout) can be used in place of a switching regulator or charge pump. The dropout characteristics for the circuit are shown in Fig. 8-95, and depend primarily on the characteristics of Q1. When the circuit is used with low voltage, such as a three-cell battery, Q1 must have a gate-threshold voltage below that of the lowest battery voltage. For example, the RDS(ON) for the Si9433 is guaranteed at a VGS of 2.7 V. The circuit will operate at input voltages from 3 V to 15 V. The quiescent current (VIN = 6.5 V) is 40 μA when the circuit is operated in the low-power mode, but it increases to 70 μA in the high-power mode. The maximum load current is 1 A in high-power and 5 mA in low-power. The high - and low-power modes are selected by logic at the MODE SELECT input. High-power mode is selected when the input is high. MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994, P. 15.   (View)

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Tachless_motor_speed_controller

Published:2009/7/24 23:28:00 Author:Jessie

This circuit is particularly applicable to digitally controlled systems in robotic and X-Y positioning applications. The circuit controls from 20 rpm to full speed (with good transient response under all shaft conditions) by sensing the motor's back EMF to determine speed. The difference between the speed and a setpoint is used to close a sampled loop around the motor. A1 generates a pulse train. When the A1 output is high, Q1 is biased, Q3 turns off, and the motor back EMF appears after the inductive flyback stops, During this period, the S1 (a switch within the CD4016) input is turned on, and the 0.047-μF capacitor charges to the back EMF value. A2 compares this value with the setpoint, and the amplifier difference changes the A1 duty cycle, thus controlling motor speed. The setpoint is controlled by a -3-V signal (Ein) at the A2 noninverting input.   (View)

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5_V_from_four_cells_linear_regulation

Published:2009/7/24 23:35:00 Author:Jessie

Figure 8-98 shows a MAX667 linear regulator connected to provide a 5-V output from four cells. The input voltage range is 4 V to 16.5 V. The quiescent current (VIN = 6 V) is 10 μA, and the maximum load current (VIN = 6 V) is 250 mA. The dropout voltage is 100 mV with a 100-mA load. Figure 8-99 shows the efficiency curves. MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994, P. 21.   (View)

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FSK_decoding_with_carrier_detect

Published:2009/7/24 23:35:00 Author:Jessie

This circuit is similar to that of Fig. 3-9, but it also uses the lock-detect section of the XR-2211 (Fig. 3-9C) as a carrier-detect option for FSK decoding. The lock-detect output at pin 6 is shorted to the data output at pin 7. The data output is disabled in the low state until there is a carrier within the detection band of the PLL, and pin 6 goes high to enable the data output. The minimum value of lock-detect filter capacitance CD (pins 3 and 4) can be calculated using: CD (inμF)=16/capture range in Hz. Large values of CD slow response time of the lock-detect output, and small CD values can result in chatter on the lock-detect output as an incoming signal approaches the capture-bandwidth frequency.   (View)

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Frequency_shift_decoder_FSK

Published:2009/7/24 23:34:00 Author:Jessie

This circuit shows an XR-2211 connected for FSK decoding. Recommended component values for some of the most commonly used FSK bands are given in Fig. 3-9B. Internal functions of the XR-2211 are given in Fig. 3-9C. The.circuit can be tailored for any FSK-decoding application by the choice of R0, R1,C0, C1, and CF. For a given set of FSK mark and space frequencies, f1 and f2, these parameters can be calculated as follows: Calculate PLL center frequency fo using: Use 18 kΩ for R0 so that R0 can be set to 20 kΩ with the series Rx pot. Calculate the value of C0 using: C0=1/R0f0.Calculate R1 to give a difference frequency equal to the mark-space deviation: R1= R0[(f0/f1--/f2)].Calculate C1 (which sets the loop-filter time constant) using: C1= C0/4.Calculate CF (which is the data-filter capacitance with RF=100 kΩ and RF= 510 kΩ) using: CF (inμF) =3/baud rate. All calculated values, value. except R0, can be rounded off to the nearest standard walue .R0 can be fine tuned with Rx.   (View)

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33_Vfrom_four_to_six_cells

Published:2009/7/24 23:33:00 Author:Jessie

Figures 8-96 and 8-97 show two circuits that provide 3.3 V with four- to six-cell inputs. Both circuits can be switched (by an LP/HP control signal) between high-and low-power modes to accommodate equipment that operates in two modes. The circuit of Fig. 8-96 has a quiescent current of 60 μA (VIN = 4.8 V) in the LP mode and 1.6 mA in the HP mode. Maximum load current (VIN = 4 V) in LP is 10 mA, and 400 mA in HP. Efficiency (VIN = 4.8 V) in LP is 72%, with a 1-mA load, and 92% in HP, with a 100-mA load. The circuit of Fig. 8-97 has a quiescent current (VIN = 4.8 V) in the LP mode of 25 pA and 1.6-mA in HP. The maximum load current (VIN = 4 V) in LP is 50 mA, and 400 mA in HP. Efficiency (VIN = 4.8 V) in LP is 86%, with a 1-mA load, and 92% in HP, with a 100-mA load. MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994, P. 17.   (View)

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Low_dropout_linear_regulator

Published:2009/7/25 4:21:00 Author:Jessie

Figure 8－126 shows a MAX666 linear regulator connected to provide a 5-V output. This circuit is useful for uninterruptible battery-backup applications, as well as forlow-power circuits that use batteries for maln power and optionally take powerfrom wall-cube ac adapters．The input-voltage range is 5.4 V to 16.5 V, quiescent current(VIN ＝10 V) is 20 μA, dropout voltage (with 100－mA load) is 400 mV，maximum load current (VIN＝6 V) is 500 mA and shutdown current is 5 μA，Figure 8-127 shows the efficiency curves．Notice that the pass transistor is externaland can be sized to handle the required power dissipation．If the dissipation is lowenough the MAX666 internal 50-mA power transistor can replace the 2N2905．TheMAX667 should also be considered In such cases. (The MAX667 has a larger, 250－mA pass transistor and lower dropout voltage.) MAXIM BATTERY MANAGEMENT CIRCUIT COLLECTION, 1994, P. 74．   (View)

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