NJM2352 LOW POWER SWITCHING REGULATOR ■ GENERAL DESCRIPTION The NJM2352 is the industry's first monolithic low power switching regulators available in an 8-lead mini-DIP, and designed specifically for battery operated instruments. They each contain a 1.3V temperature compensated bandgap reference, adjustable free running oscillator, voltage comparator, low battery detection circuitry, and a 200mA switch transistor with all of the functions required to make a complete low power switching regulator. These regulators can achieve up to 80% efficiency in most applications while being able to operate over a wide input supply voltage range, 2.6V to 24V at a very low quiescent drain of 280µA. The NJM2352 can be used as a building block in three basic applications : step-up, step-down and inverting. ■ PACKAGE OUTLINE NJM2352D NJM2352M ■ FEATURES • Operating Voltage (2.6V to 24.0V) • Low Operating Current • Internal Low Voltage Detect Circuit • Pulse Width Modulation Control Circuit • Package Outline DIP8, DMP8 • Bipolar Technology ■ BLOCK DIAGRAM NJM2352D NJM2352M Ver.2003-07-18 -1- NJM2352 ■ ABSOLUTE MAXIMUM RATINGS PARAMETER (Ta = 25ºC) SYMBOL RATINGS UNIT + Supply Voltage V 24 V Power Dissipation PD (DIP8) 500 (DMP8) 300 mW mW Operating Temperature Range Topr -40 to + 85 ºC Storage Temperature Range Tstg -40 to +125 ºC ■ ELECTRICAL CHARACTERISTICS DC Electrical Characteristics (V+ = 6V, Ta = 25ºC) PARAMETER Operating Current (1) Operating Current (2) Reference Voltage Sw. Saturation Voltage Sw. Current SYMBOL Sw. Leakage Current ICC (1) ICC (2) VREF VSW ISW ISWO Operating Frequency Low Battery Output Current Low Battery Output Leakage Current FO ILED (L) ILED (H) TEST CONDITION + V = 24V ISW = 100mA VSW = 0.4V V 3 PIN = 24V CX = 50pF V 1 PIN = 1.1V, V 8 PIN = 0.4V V 1 PIN = 1.4V, V 8 PIN = 6V MIN. TYP. MAX. UNIT 1.24 100 275 400 1.31 0.2 200 350 550 1.38 0.4 - µA µA V V mA - 0.1 10 µＡ 40 300 - 50 800 0.1 60 5 kHz µA µA MIN. TYP. MAX. UNIT 8.51 4.72 22.7 9.00 100 50 5.00 24.0 9.49 200 200 5.28 25.3 V mV mV V V AC Electrical Characteristics (STEP-UP. Ta = 25ºC) PARAMETER Output Voltage (9V Set) Load Regulation (9V Set) Line Ragulation (9V Set) Output Voltage (5V Set) Output Voltage (24V Set) SYMBOL VO(9) ∆VO-IO (9) ∆VO-VIN (9) ILED (L) ILED (H) TEST CONDITION + V = 4.5V, IO = 10mA + V = 4.5V, IO = 2 to 17mA + V = 4.5V to 8.1V, IO = 10mA + V = 2.6V, IO = 10mA + V = 12V, IO = 4mA ■ TEST CIRCUIT D2:SBD (EK-14) -2- Ver.2003-07-18 NJM2352 ■ TYPICAL APPLICATION 1. Step-Up Switching Regulator (Low Current) 2. Step-Up Switching Regulator (High Current) Ver.2003-07-18 -3- NJM2352 ■ TYPICAL APPLICATION 3. Step-Down Switching Regulator 4. Inverting Switching Regulator -4- Ver.2003-07-18 NJM2352 ■ DESIGN EQUSTIONS Component Step Up Step Down Inverting R1 R1=R3×10 R1=R3×10 R1=R3×10 R2 VTH − VREF 5µA VTH − VREF 5µA VTH − VREF 5µA VOUT − VREF VOUT − VREF VOUT I1 I1 I1 VREF VREF VREF I1 I1 I1 R5 261Ω 261Ω 261Ω Cx (pF) 2.14 × 10 6 FO (Hz) 2.14 × 10 6 FO 2.14 × 10 6 FO Lx 0.3 ⋅ VBAT ⋅ (VOUT − VBAT) FO ⋅ ILOAD ⋅ VOUT 0.3 ⋅ ( VOUT) FO ⋅ ILOAD 0.3 ⋅ VBAT ⋅ VOUT C1 0.15ILOAD(2VOUT − VBAT) 2 FO ⋅ VOUT ⋅ VR ⋅ VBAT ILOAD 4FO ⋅ VR 0.15 ⋅ ILOAD ⋅ (VBAT + 2 VOUT ) 2 R6 35 ⋅ VBAT ILOAD ⋅ VOUT 35 ILOAD 35 ⋅ VBAT ILOAD ⋅ (VBAT + VOUT ) R7 5 ⋅ (VBAT) 2 ILOAD ⋅ VOUT 5 ⋅ VBAT ILOAD 5 ⋅ (VBAT) 2 ILOAD ⋅ (VBAT + VOUT ) R8 350 ⋅ VBAT ILOAD ⋅ VOUT R9 50(VBAT) 2 ILOAD ⋅ VOUT R3 R4 FO ⋅ ILOAD ⋅ ( VBAT + VOUT ) FO ⋅ VBAT ⋅ (VBAT + VOUT ) ⋅ VR I1 = 100µA VTH : low battery detection voltage. Ripple Voltage at VR : I1 = 50 to 100µA. Ver.2003-07-18 -5- NJM2352 ■ DESCRIPTION The NJM2352 is a micro-power switching regulator control IC suitable for a equipment of battery operation and may be used as step-up, step-down and inverting regulators. The NJM2352 contains a reference, oscillator, amplifier, comparator, detector of input voltage drop and switching transistor. The output voltage is controled by PWM method. The NJM2352 applies a bandgap as a reference voltage. The oscillator is composed of putting one capacitance (Cx) to the pin 2. The amplifier is 80dB open-loop voltage gain and 1MHz band width. By adding adequate resistors to the pin 1, the indicating signal comes when the input voltage drops more than designed input voltage. Switching transistor is open collector. ■ TERMINAL DESCRIPTION TERMINAL NO. -6- TERMINAL ITEMS FUNCTION 1 Input of Voltage Drop Detector Inverting input Terminal of comparator-3. When input voltage drops than non-inverting input voltage, comparator drives indicator output transistor. 8 Output of Voltage Drop Detecctor Open collector output transistor for driving LED, LCD etc. INSIDE EQUIVALENT CIRCUITS Ver.2003-07-18 NJM2352 ■ TERMINAL DESCRIPTION TERMINAL NO. TERMINAL ITEMS FUNCTION 2 Timing C 3 Switching Transistor Open collector Output of Output switching transistor. 4 GROUND Ground 5 V+ Supply voltage terminal. Ver.2003-07-18 INSIDE EQUIVALENT CIRCUITS Connecting timing for deciding oscillator frequency. -7- NJM2352 ■ TERMINAL DESCRIPTION TERMINAL NO. -8- TERMINAL ITEMS FUNCTION 6 NF2 Terminal from connecting point of AMP output and COMP-1 inverting input. 7 NF1 Inverting input of amplifier. INSIDE EQUIVALENT CIRCUITS Ver.2003-07-18 NJM2352 ■ PRINCIPLE OF OPERATION The NJM2352 circuit block is shown on Fig. 1 and timing chart on Fig. 2. Function of COMP-2 is setting dead-time. At point A is the square wave and at point B is the triangular wave. By putting two input signals (A, B) into COMP-2, output (point C) voltage is held high level during rising period of triangular wave and the switching transistor is kept in the off condition regardless the COMP-1 output level. So the maximum duty cycle of the NJM2352 is 50%. The COMP-1 makes on-time of switching transistor longer when the output voltage is high and shorter when it is low. Thus function of the COMP-1 is pulse wide modulation. When the AMP's output waveform is D, COMP-1 output is like E, and NOR GATE output becomes high level only when both inputs, C, E, are low, and so the falling period of triangular wave is the range of pulse width control. D B E F A C A D B E C F Ver.2003-07-18 -9- NJM2352 ■ MINIMUM OPERATING VOLTAGE Minimum operating voltage is V+ ≥ 2.6V at 25°C and its temperature coefficient is negative. Be careful when you design. Less than this minimum operating voltage, internal switching transistor becomes on, and the surge-like high current flows into it especially in Step-Up or Inverting application. ■ OSCILLATOR Oscillator frequency is decided by putting a capacitor into PIN 2. The amplitude of both square wave A and triangular wave B is between 1 VBE and 3VBE. ■ AMPLIFIER AMP source current it 20 µA max. and so the feedback resistor R1 to be connected to PIN 6 and PIN 7 are recommended more than 100kΩ. ■ SWITCHING TRANSISTOR When the negative voltage more than 0.5V absolute value based on ground level is applied, the NJM2352 may operate unordinary by reason of parasitic effect in it. And so put SBD in between PIN 3 and ground when you drive directory coil with internal switching transistor. NJM2352 ■ DETECTION CIRCUIT OF INPUT VOLTAGE DROP When input voltage becomes lower than specified voltage, transistor Q56 switches on and indicative device like LED turns on. The specified voltage is decided by internal reference voltage and outer resistors ratio. VTH = VREF (1+R2/R5) + R2 x 0.5µA When - input voltage becomes lower than + input voltage, PIN 1 of COMP-3 sinks about 1µA and thus prevents chattering. Transistor Q56 becomes off condition when PIN 1 voltage is lower than about 0.2V. It is recommendable to put about 1µF to PIN 1 in actual application to avoid switching noise. - 10 - Ver.2003-07-18 NJM2352 ■ EFFICIENCY Efficiency is shown below. Set Up = VIN − VS VIN Step Down = Inverting = VOUT VOUT + VD − VS x VIN − VS + VD VIN VIN − VS VIN x x VOUT VOUT + VD VOUT VOUT + VD VS : Voltage Drop based on switching transistor On-Resistance. VD : Diode Forward Voltage Drop. If VS and VD are low, efficiency increase. Also speed of switching transistor and diode, series resistance of L will affect to it. Example is shown on typical characteristic graph. ■ TEST CIRCUIT 2 (VOUT : 9V) ■ PARAMETER • D1 EK-14 IS1588 • LX = 470µH L1 : Ingernal Resistance = 0.2Ω L2 : Ingernal Resistance = 2Ω L3 : Ingernal Resistance = 7Ω Ver.2003-07-18 - 11 - NJM2352 ■ TYPICAL CHARACTERISTICS Operating Current Reference Voltage Operating Frequency Operating Frequency VCE (No. 8 Pin) Switching Tr Saturation Voltage - 12 - Ver.2003-07-18 NJM2352 ■ TYPICAL CHARACTERISTICS Minimum Operating Input Voltage Voltage Gain No.1 Pin Input Current Ver.2003-07-18 - 13 - NJM2352 ■ TYPICAL CHARACTERISTICS (APPLICATION) Output Voltage Output Voltage - 14 - Efficiency Output Voltage Ver.2003-07-18 NJM2352 ■ TYPICAL CHARACTERISTICS (Test Circuits 2) Efficiency Ver.2003-07-18 Output Voltage Efficiency Output Voltage Input Current Output Voltage - 15 - NJM2352 [CAUTION] The specifications on this databook are only given for information , without any guarantee as regards either mistakes or omissions. The application circuits in this databook are described only to show representative usages of the product and not intended for the guarantee or permission of any right including the industrial rights. - 16 - Ver.2003-07-18