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UTC L2800
LINEAR INTEGRATED CIRCUIT
SWITCHING REGULATOR CONTROLLER(LOW VOLTAGE)
DESCRIPTION
The UTC L2800 is a single-channel switching regulator control IC for low voltage applications incorporating a soft start function and short circuit detection function. The device has a low minimum operating voltage of 1.8V and is ideal for the power supply of battery-operated electronic equipment.
SOP-8
FEATURES
*Wide supply voltage operating range: 1.8V~15V *Low current consumption: Typically 5.5mA in operation,1A or less in stand-by *High speed operation is possible: Maximum 1MHz *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.
TSSOP-8
PIN CONFIGURATION
-IN SCP
1
8
FB
2
7
OSC
Vcc
3
6
GND OUT
BR/CTL
4
5
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UTC L2800
PIN DESCRIPTION
PIN NO.
1 2 3 4 5 6 7 8
LINEAR INTEGRATED CIRCUIT
I/O
I I O O
SYMBOL
-IN SCP VCC BR/CTL OUT GND OSC FB
DESCRIPTION
Error amplifier inverting input pin Soft start and SCP setting capacitor connection pin Power supply pin Output current setting and control pin Totem-pole type output pin Ground pin Capacitor and resistor connection pin for setting the oscillation frequency Error amplifier output pin
BLOCK DIAGRAM
Vcc 3 OSC 7
Reference voltage supply 1.25V -IN 1 + 0.5V FB 8
0.6V 0.1V 36k
Sawtooth wave oscillator 0.1V + + + PWM Comp. Output drive control circuit 0.3V 5 30k OUT
Error Amp.
500
DTC 0.6V
Soft start SCP
6 GND
2 SCP
4 BR/CTL
ABSOLUTE MAXIMUM RATINGS (Ta=25)
PARAMETER
Power Supply Voltage Output Source Current Output Sink Current Power Dissipation SOP-8 TSSOP-8
SYMBOL
Vcc IO+ IOPD
RATINGS
16 -50 50 570* 580* -55 ~ +125 -30 ~ +85
UNIT
V mA mA mW C C
Storage Temperature Tstg Operating Temperature Top * When mounted on a 10cm square double-sided epoxy board.
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UTC L2800
PARAMETER
LINEAR INTEGRATED CIRCUIT
SYMBOL
Vcc VI VBR IO+ IOCPE CP RB RT CT fosc Top
RECOMMENDED OPERATING CONDITIONS (Ta=25C)
MIN
1.8 -0.2 -0.2 -40 0.1 0.1 390 3.0 270 500 +25
TYP
MAX
15 1.0 Vcc 40
UNIT
V V V mA mA F F k pF kHz C
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
150 1.0 100 10 -30
5000 10.0 10000 1000 +85
ELECTRICAL CHARACTERISTICS (Ta=25C, VCC=+2V)
PARAMETER
Circuit to prevent Reset Voltage malfuncition at low input Threshold Voltage oltage (U.V.L.O) Soft Start Charging Current Voltage at soft start completion Short Circuit Charging Current Detection(S.C.P.) Threshold Voltage Sawtooth Wave Oscillation Frequency Oscillator(OSC) Frequency Input Stability Frequency Variation With Temperature Error Amplifier Input Threshold Voltage VT Input Stability VT Variation With Temperature Input Bias Current Voltage Gain Frequency Bandwidth Maximum Output Voltage Range Output Source Current Output Sink Current Idle Period Adjustment Maximum Duty Cycle Section Output Section Output Voltage
SYMBOL
VR VTH Ics Vts Icpc VtPC fosc fdV fdT VT VTdV VTdT IB Av BW VOM+ VOMIOM+ IOMtDUTY VOH1 VOH2 VOL1 VOL2 IO+ IORO
TEST CONDITIONS
MIN
TYP MAX UNIT
0.9 V V A V A V kHz % % 520 20 1.0 145 mV mV % A V/V MHz V V A A % V V 0.2 0.2 -20 40 V V mA mA k
1.1 VSCP=0V -1.5 0.7 VSCP=0V RT=3.0k, CT=270pF Vcc=2V ~ 15V Ta=-30C ~ +85C VFB=450mV Vcc=2V ~ 15V Ta=-30C ~ +85C VIN=0V AV=0dB 0.78 VFB=0.45V 24 RT=3.0k, CT=270pF VFB=0.8V RB=390, Io=-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 65 1.0 0.8 480 -1.5 0.7 400
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 0.1 0.1
1.5 -0.7 0.9 -0.7 0.9 600 10
-1.0 70
0.2 -24 85
Output Source Current Output Sink Current Pull Down Resistance
30 20
-30 60 30
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PARAMETER
LINEAR INTEGRATED CIRCUIT
SYMBOL
VBR IOFF ION IBR ICCS ICC
TEST CONDITIONS
RB=390
MIN
0.2 -20 -1.8
TYP MAX UNIT
0.3 0.4 0 -45 -0.1 1 9.3 V A A mA A mA
Output Current Setting Pin Voltage Section/Control Section Input Off Condition Input On Condition Pin Current Range Entire Device Stand-by Current Average Supply Current
BR/CTL pin open or Vcc RB=390
5.5
DIAGRAM
FB pin voltage Reference input for short circuit detection comparator Idle period setting voltage Sawtooth wave output Soft start setting voltage
OUT pin waveforms
SCP pin waveforms
Soft start ts ON Power supply control SW OFF
tPE Output short circuit Output short circuit
Short circuit detection
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 sawtooth 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*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*CPE[F]
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LINEAR INTEGRATED CIRCUIT
Supply Voltage vs.Input Threshold Voltage
TYPICAL CHARACTERISTICS
Supply Voltage vs.Supply Current
Input threshold Voltage ,VT (V)
10
Supply current ,Icc (mA)
Ta=+25 RB=390
1.0 0.8 0.6 0.4 0.2 0
Ta=+25
8 6 4 2 0
0
4
8 12 Supply voltage ,Vcc ( V )
16
20
0
4
8 12 16 Supply voltage ,Vcc ( V )
20
Supply Voltage vs.Input Threshold Voltage
Ta=+25 Input threshold voltage variation ration ,VT/VT (%)
Ambient Temperature vs. Input Threshold Voltage Variation Ratio 10
Vcc=2V
1.0 Input threshold voltage ,VT (V) 0.8 0.6 0.4 0.2 0
5
0
-5
-10
0
1.0
2.0 3.0 4.0 Supply voltage ,Vcc ( V )
5.0 -15 -40 -20 0 20 40 60 Ambient temperature ,Ta ( ) 80 100
High Level Output Low level output voltage ,V (mV) OUT Low level output voltage ,V (V) OUT 2.0 1.6 1.2 0.8 0.4 0
Vcc=2V Ta=+25 RB=390
Low Level Output 500 400 300 200 100 0
Vcc=2V Ta=+25 RB=390
0
-10
-20
-30
-40
-50
0
High level output current ,IOUT(mA)
80 20 40 60 High level output current ,IOUT(mA)
100
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Output source current ,IOUT (mA) -50 -40 -30 -20 -10 0
LINEAR INTEGRATED CIRCUIT
BR/CTL Pin Current vs. BR/CTL Pin Voltage 500 BR/CTL pin voltage ,VBR (mV) 400 300 200 100 0
Vcc=2V Ta=+25
BR/CTL Pin Current vs. Output Source Current
Vcc=2V VOUT=0.9V Ta=+25
0
-0.4
-0.8
-1.2
-1.6
-2.0
0
-0.4
-0.8
-1.2
-1.6
-2.0
BR/CTL pin Current ,I BR (mA)
BR/CTL pin current ,I BR (mA)
BR/CTL Pin Current vs. Supply Current 5.0 Supply current ,I CC (mA) 4.0 3.0 2.0 1.0 0 1M Oscillation frequency ,fosc (Hz) 500k 200k 100k 50k 20k 10k 5k 2k
Timing Resistor vs. Oscillation Frequency
CT=100pF Vcc=2V Ta=+25
Vcc=2V Ta=+25
CT=1000pF
CT=10000pF
0
-20
-80 -60 BR/CTL pin current ,I BR (A)
-40
-100
1k
2k 5k 10k Timing resistor ,R T ()
20k
Supply Voltage vs. Frequency Variation Ratio 10
Frequency variation ratio ,f/f (%) Frequency variation ratio ,f/f (%) CT=270pF Ta=+25 RT=3.0k
Ambient Temperature vs. Frequency Variation Ratio 10
Vcc=2V CT=270pF RT=3.0k
5
5
0
0
-5
-5
-10
-10
-15
0
2
8 4 6 10 Supply voltage ,Vcc (V)
12
14
16
-15 -40
-20
60 0 20 40 Ambient temperature ,Ta ()
80
100
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100
Maximum duty cycle, tDUTY (%)
LINEAR INTEGRATED CIRCUIT
Oscillation Frequency vs.Maximum Duty Cycle
Vcc=2V CT=270pF Ta=+25
80 60 40 20 0 10K
100K 1M Oscillation frequency ,fosc (Hz)
Output Pin Voltage and Current Waveforms (Reference Data) (V) 6 4
VOUT
2V
Vcc=2V CT=270pF RT=1.0k
2
0 (mA) 50
IOUT
0 -50 10mV 0 0.4 0.8 1.2 200ns 1.6 2.0
t (s)
Note:The OFF delay time of VOUT depends on the characteristics of the external transistor.
Vcc 22H
(5V)
UTC L2800 5 IOUT
18k VOUT 10F 2k
4
390
-IN Measurement Circuit Diagram
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LINEAR INTEGRATED CIRCUIT
FUNCTIONAL DESCRIPTION
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(pin 30).In addition to providing the reference voltage for the switching regulator, the circuit also sets the idle period. (2) SAWTOOTH WAVE OSCILLATOR The sawtooth oscillator generates a sawtooth 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 sawtooth 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(pin 4). 2. POWER SUPPLY CONTROL FUNCTION Stand-by mode(supply current 1A or less) can be set by connecting the BR/CTL pin(pin 4) to Vcc or by making the pin open circuit.
UTC L2800 4 RB SW
SW
OFF ON
MODE
Stand-by mode Operating mode
BR/CTL
3. OTHER FUNCTIONS (1) SOFT START AND SHORT CIRCUIT DETECTION Soft start operation is set by connecting capacitor CPE to 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 0.8V,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 "HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION")
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UTC L2800
LINEAR INTEGRATED CIRCUIT
(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
18k 22H VO 5V
-IN VIN 3V SCP Vcc 33F 2k BR/CTL 0.1F
1 2 3 4
8 7 6 5
FB OSC GND OUT 10F
390 270pF 3k 0.1F
CTL
UTC assumes no responsibility for equipment failures that result from using products at values that exceed, even momentarily, rated values (such as maximum ratings, operating condition ranges, or other parameters) listed in products specifications of any and all UTC products described or contained herein. UTC products are not designed for use in life support appliances, devices or systems where malfunction of these products can be reasonably expected to result in personal injury. Reproduction in whole or in part is prohibited without the prior written consent of the copyright owner. The information presented in this document does not form part of any quotation or contract, is believed to be accurate and reliable and may be changed without notice.
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