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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 280A. The NJM2352 can be used as a building block in three basic applications : step-up, step-down and inverting. 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 PACKAGE OUTLINE
NJM2352D
NJM2352M
NJM2352D NJM2352M
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NJM2352
ABSOLUTE MAXIMUM RATINGS
PARAMETER Supply Voltage Power Dissipation Operating Temperature Range Storage Temperature Range SYMBOL V
+
(Ta = 25C)
RATINGS 24 (DIP8) 500 (DMP8) 300 -40 to + 85 -40 to +125 UNIT V mW mW C C
PD Topr Tstg
ELECTRICAL CHARACTERISTICS DC Electrical Characteristics (V+ = 6V, Ta = 25C)
PARAMETER Operating Current (1) Operating Current (2) Reference Voltage Sw. Saturation Voltage Sw. Current Sw. Leakage Current Operating Frequency Low Battery Output Current Low Battery Output Leakage Current SYMBOL ICC (1) ICC (2) VREF VSW ISW ISWO FO ILED (L) ILED (H) 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
+
TEST CONDITION
MIN. 1.24 100 40 300 -
TYP. 275 400 1.31 0.2 200 0.1 50 800 0.1
MAX. 350 550 1.38 0.4 10 60 5
UNIT A A V V mA kHz A A
AC Electrical Characteristics (STEP-UP. Ta = 25C)
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
MIN. 8.51 4.72 22.7
TYP. 9.00 100 50 5.00 24.0
MAX. 9.49 200 200 5.28 25.3
UNIT V mV mV V V
TEST CIRCUIT
D2:SBD (EK-14)
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NJM2352
TYPICAL APPLICATION 1. Step-Up Switching Regulator (Low Current)
2. Step-Up Switching Regulator (High Current)
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NJM2352
TYPICAL APPLICATION 3. Step-Down Switching Regulator
4. Inverting Switching Regulator
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DESIGN EQUSTIONS Component R1 R2 R3 R4 R5 Cx (pF) Lx C1 R6 R7 R8 R9 I1 = 100A VTH : low battery detection voltage. Ripple Voltage at VR : I1 = 50 to 100A. Step Up R1=R3x10
VTH - VREF 5A
Step Down R1=R3x10
VTH - VREF 5A
Inverting R1=R3x10
VTH - VREF 5A
VOUT - VREF
I1
VOUT - VREF
I1
VOUT
I1
VREF
I1
VREF
I1
VREF
I1
261
2.14 x 10 6 FO (Hz) 0.3 VBAT (VOUT - VBAT) FO ILOAD VOUT
261
2.14 x 10 6 FO 0.3 ( VOUT) FO ILOAD
261
2.14 x 10 6 FO
0.3 VBAT VOUT FO ILOAD ( VBAT + VOUT ) 0.15 ILOAD (VBAT + 2 VOUT ) 2 FO VBAT (VBAT + VOUT ) VR 35 VBAT ILOAD (VBAT + VOUT )
0.15ILOAD(2VOUT - VBAT) 2 FO VOUT VR VBAT
35 VBAT ILOAD VOUT
ILOAD 4FO VR
35 ILOAD
5 (VBAT) 2 ILOAD VOUT
350 VBAT ILOAD VOUT
50(VBAT) 2 ILOAD VOUT
5 VBAT ILOAD
5 (VBAT) 2 ILOAD (VBAT + VOUT )
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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. 1 TERMINAL ITEMS Input of Voltage Drop Detector FUNCTION Inverting input Terminal of comparator-3. When input voltage drops than non-inverting input voltage, comparator drives indicator output transistor. INSIDE EQUIVALENT CIRCUITS
8
Output of Voltage Drop Detecctor
Open collector output transistor for driving LED, LCD etc.
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TERMINAL DESCRIPTION TERMINAL NO. 2 TERMINAL ITEMS Timing C FUNCTION Connecting timing for deciding oscillator frequency. INSIDE EQUIVALENT CIRCUITS
3
Switching Transistor Open collector Output of Output switching transistor.
4 5
GROUND V+
Ground Supply voltage terminal.
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NJM2352
TERMINAL DESCRIPTION TERMINAL NO. 6 TERMINAL ITEMS NF2 FUNCTION Terminal from connecting point of AMP output and COMP-1 inverting input. INSIDE EQUIVALENT CIRCUITS
7
NF1
Inverting input of amplifier.
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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
E
B
F A C
A D B E
C
F
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NJM2352
MINIMUM OPERATING VOLTAGE Minimum operating voltage is V+ 2.6V at 25C 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 A max. and so the feedback resistor R1 to be connected to PIN 6 and PIN 7 are recommended more than 100k. 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 0.5A When - input voltage becomes lower than + input voltage, PIN 1 of COMP-3 sinks about 1A 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 1F to PIN 1 in actual application to avoid switching noise.
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EFFICIENCY Efficiency is shown below. Set Up =
VIN - VS VIN
x
VOUT VOUT + VD - VS
Step Down = Inverting =
VIN - VS + VD VIN
x
VOUT VOUT + VD
VIN - VS VIN
x
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 = 470H L1 : Ingernal Resistance = 0.2 L2 : Ingernal Resistance = 2 L3 : Ingernal Resistance = 7
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TYPICAL CHARACTERISTICS Reference Voltage Operating Current
Operating Frequency Operating Frequency
VCE (No. 8 Pin) Switching Tr Saturation Voltage
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TYPICAL CHARACTERISTICS
Minimum Operating Input Voltage
Voltage Gain
No.1 Pin Input Current
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TYPICAL CHARACTERISTICS (APPLICATION) Output Voltage Efficiency
Output Voltage
Output Voltage
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TYPICAL CHARACTERISTICS (Test Circuits 2) Efficiency
Output Voltage
Efficiency
Output Voltage
Input Current
Output Voltage
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[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.
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