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| PJ3800 Low Voltage Switching Regulator Controller T he PJ3800 is a single-channel switching regulator control IC for low voltage applications incorporating a soft start function and short circuit detection function. SOP-8 TSSOP-8 The device has a low minimum operating voltage of 1.8 V and is ideal for the power supply of battery-operated electronic equipment. . FEATURES Wide supply voltage operating range: 1.8 to 15 V Low current consumption: Typically 5.5 mA in operation, 1 mA or less in stand-by High speed operation is possible: Maximum 1 MHz The error amplifier gain is set inside the IC, so peripheral components are minimized. Incorporates a soft start circuit. Incorporates a timer-latch type short circuit detection circuit (SCP). Totem-pole type output with adjustable on/off current (for NPN transistors) Incorporates a stand-by function. Pin 1. Error amplifier inverting input 2. Soft Star & SCP 3. Power supply 4. Output current setting and control 5. Output 6. Ground 7. Oscillation frequency 8. Error amplifier output ORDER INFORMATION Device PJ3800CS PJ3800CA Operation Temperature -20 ~ +85 Package SOP-8 TSSOP-8 BLOCK DIAGRAM 1-8 2003/04.rev.A PJ3800 Low Voltage Switching Regulator Controller ABSOLUTE MAXIMUM RATINGS Parameter Power supply voltage Output source current Output sink current Allowable dissipation Operating temperature Storage temperature Symbol VCC IO+ IOPD Top Tstg Rated Value Min. -- -- -- -- -30 -55 Max. 16 -50 50 570* +85 +125 Unit V mA mA mW * : When mounted on a 10 cm square double-sided epoxy board WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.) in excess of absolute maximum ratings. Do not exceed these ratings. RECOMMENDED OPERATING CONDITIONS Values Min. 1.8 -0.2 -0.2 -40 -- -- -- 150 1 100 10 -30 Typ. -- -- -- -- -- 0.1 0.1 390 3 270 500 +25 Max. 15 1 VCC -- 40 -- -- 5000 10 10000 1000 +85 Parameter Power supply voltage Error amplifier input voltage BR/CTL pin input voltage Output source current Output sink current SCP pin capacitance Phase compensation capacitance Output current setting resistance Timing resistance Timing capacitance Oscillation frequency Operating temperature Symbol VCC VI VBR IO+ IO- CPE CP RB RT CT fOSC TOP Unit V V V mA mA F F k pF kHz WARNING: Recommended operating conditions are normal operating ranges for the semiconductor device. All the device's electrical characteristics are warranted when operated within these ranges. Always use semiconductor devices within the recommended operating conditions. Operation outside these ranges may adversely affect reliability and could result in device failure. No warranty is made with respect to uses, operating conditions, or combinations not represented on the data sheet. Users considering application outside the listed conditions are advised to contact their Promax Johnton representative beforehand. 2-8 2003/04.rev.A PJ3800 Low Voltage Switching Regulator Controller ELECTRICAL CHARACTERISTICS (VCC = +2 V, Ta = +25 C) Parameter Circuit to prevent Reset voltage malfunction at low input voltage (U.V.L.O.) Threshold voltage Charging current Soft start Voltage at soft start completion Short circuit detection (S.C.P.) Saw tooth wave oscillator (OSC) Charging current Threshold voltage Oscillation frequency Frequency input stability Frequency variation with temperature Input threshold voltage VT input stability VT variation with temperature Input bias current Error amplifier Voltage gain Frequency bandwidth Maximum output voltage range Output source current Output sink current Idle period adjustment section Maximum duty cycle Symbol V VTH ICS VtS ICPC VtPC fOCS fdV fdT VT VTdV VTdT IB AV BW VOM+ VOMIOM+ IOMtDUTY VOH1 VOH2 Output voltage Output section Output source current Output sink current Pull down resistance Pin voltage Output current setting section/ Control section Input off condition Input on condition Pin current range Entire device Stand-by current Average supply current t VOL1 VOL2 IO+ IORO VBR IOFF ION IBR ICCS ICC BR/CTL pin open or VCC RB = 390 -- Condition -- VSCP = 0 V -- VSCP = 0 V -- RT=3.0k, CT = 270 pF VCC = 2 V to 15 V Ta =-20 to +85 VFB = 450 mV VCC = 2 V to 15 V Ta =-20 to +85 VIN = 0 V -- AV = 0 dB -- VFB = 0.45 V RT=3.0k,CT =270pF VFB =0.8V RB = 390IO =-15mA RB=750,VCC=1.8V IO = -10mA RB = 390,IO=15mA RB = 750 VCC=1.8V IO = 10mA RB = 390 VO = 0.9V RB = 390 VO = 0.3V -- RB = 390 Value Min. -- 1.1 -0.5 0.7 -1.5 0.7 400 -- -- 480 -- -- -1.0 70 -- 0.78 -- -- 24 65 1.0 0.8 -- -- -- 30 20 0.2 -20 -- -1.8 -- -- Typ. -- 1.3 -1.0 0.8 -1.0 0.8 500 2 5 500 5 1 -0.2 100 6 0.87 0.05 -40 40 75 1.2 1 0.1 0.1 -30 60 30 0.3 -- -- -- -- 5.5 Max. 0.9 1.5 -0.7 0.9 -0.7 0.9 600 10 -- 520 20 -- 1.0 145 -- -- 0.2 -24 -- 85 -- -- 0.2 0.2 -20 -- 40 0.4 0 -45 -0.1 1 9.3 Unit V V A V A V kHz % % mV mV % A V/V MHz V V A A % V V V V mA mA k V A A mA A mA 3-8 2003/04.rev.A PJ3800 Low Voltage Switching Regulator Controller DIAGRAM HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION 1. Soft Start At power on, the capacitor CPE connected to the SCP pin starts charging. The PWM comparator compares the soft start setting voltage as a proportion of the voltage at the SCP pin with the saw tooth waveform. The comparison controls the ON duty of the OUT pin, causing the soft start operation. On completion of soft start operation, the voltage at the SCP pin stays low, the soft start setting voltage stays high, and the circuit enters the output short circuit detection wait state. Soft start time (The time until the output ON duty reaches approximately 50%) tS [s] 0.35 x CPE [F] 2. Short Circuit Protection If the switching regulator output suddenly drops due to load effect, the error amplifier output (FB pin) is fixed at VOM + and capacitor CPE starts charging. When the voltage at the SCP pin reaches approximately 0.8V, the output pin is set low and the SCP pin stays low. Once the protection circuit operates, the circuit can be restored by resetting the power supply. * Short circuit detection time tPE [s] 0.8 x CPE [F] 4-8 2003/04.rev.A PJ3800 Low Voltage Switching Regulator Controller TYPICAL CHARACTERISTICS 5-8 2003/04.rev.A PJ3800 Low Voltage Switching Regulator Controller (Continued) PJ3800 PJ3800 1. Switching Regulator Function (1) Reference voltage circuit The reference voltage circuit generates a temperature-compensated reference voltage (@1.25V) from voltage supplied from the power supply pin. In addition to providing the reference voltage for the switching regulator, the circuit also sets the idle period. (2) Saw tooth wave oscillator The saw tooth oscillator generates a saw tooth wave (up to 1 MHz) that is stable with respect to the supply voltage and temperature. The capacitor and resistor that set the oscillation frequency are connected to the OSC pin (pin 7). (3) Error amplifier (Error Amp.) The error amplifier detects the output voltage of the switching regulator and outputs the PWM control signal. The voltage gain is fixed, and connecting a phase compensation capacitor to the FB pin (pin 8) provides stable phase compensation for the system. (4) PWM comparator (PWM Comp.) The voltage comparator has one inverting and three non-inverting inputs. The comparator is a voltage/pulse width converter that controls the ON time of the output pulse depending on the input voltage. The output level is high (H) when the saw tooth wave is lower than the error amplifier output voltage, soft start setting voltage, and idle period setting voltage. (5) Output circuit The output circuit has a totem pole type configuration and can drive an external NPN transistor directly. The value of the ON/OFF current can be set by a resistor connected to the BR/CTL pin . 2. Power Supply Control Function Stand-by mode (supply current 1 mA or less) can be set by connecting the BR/CTL pin to VCC or by making the pin open circuit. 6-8 2003/04.rev.A PJ3800 Low Voltage Switching Regulator Controller 3. Other Functions (1) Soft start and short circuit detection Soft start operation is set by connecting capacitor CPE to the SCP pin (pin 2). Soft start prevents a current spike on start-up. On completion of soft start operation, the SCP pin (pin 2) stays low and enters the short circuit detection wait state. When an output short circuit occurs, the error amplifier output is fixed at VOM+ and capacitor CPE starts charging. After charging to approximately 0.8 V, the output pin (pin 5) is set low and the SCP pin (pin 2) stays low. Once the protection circuit operates, the circuit can be restored by resetting the power supply. (See "n HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION".) (2) Circuit to prevent malfunction at low input voltage Transients when powering on or instantaneous glitches in the supply voltage can lead to malfunction of the control IC and cause system damage or failure. The circuit to prevent malfunction at low input voltage detects a low input voltage by comparing the supply voltage to the internal reference voltage. On detection, the circuit fixes the output pin to low. The system recovers when the supply voltage rises back above the threshold voltage of the malfunction prevention circuit. APPLICATION EXAMPLE PJ3800 USAGE PRECAUTIONS 1. Do not apply an input voltage greater than the maximum rating. Do not input voltages greater than the maximum rating as this can cause damage to the LSI 2. Use in accordance with the recommended operating conditions. The electrical characteristics of the LSI are not guaranteed if the input voltage is greater than the maximum. Also, LSI operation is unstable if the input voltage is less than the minimum. Therefore, always use in accordance with the recommended operating conditions. 3. Use a wide ground line on the printed circuit board. As the LSI uses a high frequency and therefore can generate high frequency noise, make the ground line as wide as possible. 4. Take anti-static precautions. * Use a holder for inserting the semiconductor which is anti-static or conductive. * After mounting the device on a printed circuit board, store or transport the board in a conductive bag or container. * Earth work benches, tools, and measuring equipment. * Ensure that maintenance personnel have a resistance of 250 kW to 1 MW in series between their body and earth. 7-8 2003/04.rev.A |
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