L2800L(8TSSOP) [UTC]
Switching Regulator/Controller;
| 型号： | L2800L(8TSSOP) |
| 厂家： | 
Unisonic Technologies |
| 描述： | Switching Regulator/Controller |
| 文件： | 总9页 (文件大小：94K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
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,1µA or less in stand-by
TSSOP-8
*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.
*Pb-free plating product number: L2800L
*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 CONFIGURATION
FB
-IN
1
2
3
4
8
7
6
5
SCP
OSC
GND
OUT
Vcc
BR/CTL
1
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
UTC L2800 LINEAR INTEGRATED CIRCUIT
PIN DESCRIPTION
PIN NO. SYMBOL
I/O
I
-
-
I
O
-
-
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
1
2
3
4
5
6
7
8
-IN
SCP
VCC
BR/CTL
OUT
GND
OSC
FB
Capacitor and resistor connection pin for setting the oscillation frequency
Error amplifier output pin
O
BLOCK DIAGRAM
Vcc
OSC
7
3
Reference
Sawtooth
0.6V
voltage supply
wave oscillator
5
OUT
0.1V
0.1V
30kΩ
1.25V
-
PWM
Comp.
1
8
-
+
+
+
-IN
FB
36kΩ
500Ω
Output drive
control circuit
+
Error Amp.
0.5V
0.3V
DTC 0.6V
Soft start
SCP
6
2
4
GND
SCP
BR/CTL
ABSOLUTE MAXIMUM RATINGS (Ta=25℃)
PARAMETER
Power Supply Voltage
Output Source Current
Output Sink Current
Power Dissipation
SYMBOL
Vcc
RATINGS
UNIT
V
mA
mA
16
-50
50
+
IO
-
IO
SOP-8
TSSOP-8
PD
570*
580*
mW
Storage Temperature
Operating Temperature
Tstg
Top
-55 ~ +125
-30 ~ +85
°C
°C
* When mounted on a 10cm square double-sided epoxy board.
2
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
UTC L2800 LINEAR INTEGRATED CIRCUIT
RECOMMENDED OPERATING CONDITIONS (Ta=25°C)
PARAMETER
Power Supply Voltage
SYMBOL
Vcc
MIN
1.8
TYP
MAX
15
UNIT
V
Error Amplifier Input Voltage
BR/CTL Pin Input Voltage
Output Source Current
Output Sink Current
VI
-0.2
-0.2
-40
1.0
Vcc
V
V
VBR
+
IO
mA
mA
µF
µF
Ω
kΩ
pF
kHz
°C
-
IO
40
SCP Pin Capacitance
CPE
CP
RB
RT
CT
0.1
0.1
390
3.0
270
500
+25
Phase Compensation Capacitance
Output Current Setting Resistance
Timing Resistance
Timing Capacitance
Oscillation Frequency
150
1.0
100
10
5000
10.0
10000
1000
+85
fosc
Top
Operating Temperature
-30
ELECTRICAL CHARACTERISTICS (Ta=25°C, VCC=+2V)
PARAMETER
SYMBOL
TEST CONDITIONS
MIN TYP MAX UNIT
Circuit to prevent
Reset Voltage
VR
0.9
1.5
V
malfuncition at low input
oltage (U.V.L.O)
Soft Start
Threshold Voltage
Charging Current
Voltage at soft start
completion
VTH
Ics
1.1
1.3
V
µA
V
VSCP=0V
VSCP=0V
-1.5 -1.0 -0.7
0.7 0.8 0.9
-1.5 -1.0 -0.7
0.7 0.8 0.9
Vts
Short Circuit
Detection(S.C.P.)
Sawtooth Wave
Oscillator(OSC)
Charging Current
Icpc
VtPC
fosc
µA
V
Threshold Voltage
Oscillation Frequency
Frequency Input
Stability
Frequency Variation
With Temperature
Input Threshold Voltage
VT Input Stability
VT Variation With
Temperature
400 500 600 kHz
RT=3.0kΩ, CT=270pF
fdV
fdT
Vcc=2V ~ 15V
2
5
10
%
%
Ta=-30°C ~ +85°C
Error Amplifier
VT
VTdV
VFB=450mV
Vcc=2V ~ 15V
Ta=-30°C ~ +85°C
480 500 520 mV
5
20
mV
VTdT
1
%
Input Bias Current
Voltage Gain
Frequency Bandwidth
Maximum Output
Voltage Range
Output Source Current
Output Sink Current
IB
Av
BW
VOM
VOM
IOM
IOM
VIN=0V
AV=0dB
-1.0 -0.2
1.0
µA
70
100 145 V/V
6
MHz
V
V
µA
µA
+
0.78 0.87
0.05 0.2
-
+
VFB=0.45V
-40
40
-24
-
24
65
Idle Period Adjustment
Section
Output Section
RT=3.0kΩ, CT=270pF
VFB=0.8V
RB=390Ω, Io=-15mA
RB=750Ω, Vcc=1.8V
Io= -10mA
RB=390Ω, Io=15mA
RB=750Ω, Vcc=1.8V
Io=10mA
RB=390Ω, Vo=0.9V
RB=390Ω, Vo=0.3V
Maximum Duty Cycle
Output Voltage
tDUTY
VOH1
VOH2
VOL1
VOL2
75
1.2
1.0
0.1
0.1
85
%
V
V
V
V
1.0
0.8
0.2
0.2
-20
+
Output Source Current
Output Sink Current
Pull Down Resistance
IO
-30
60
30
mA
mA
kΩ
-
IO
30
20
RO
40
3
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
UTC L2800 LINEAR INTEGRATED CIRCUIT
PARAMETER
Output Current Setting Pin Voltage
SYMBOL
VBR
TEST CONDITIONS
RB=390Ω
MIN TYP MAX UNIT
0.2
0.3
0.4
V
Section/Control Section
Input Off Condition
Input On Condition
Pin Current Range
Stand-by Current
IOFF
ION
IBR
ICCS
ICC
-20
0
-45
µA
µA
-1.8
-0.1 mA
Entire Device
BR/CTL pin open or Vcc
1
µA
Average Supply Current
5.5
9.3
mA
RB=390Ω
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
tPE
Output short circuit
Soft start
ts
Output
short
circuit
ON
Power supply control SW
OFF
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[µF]
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[µF]
4
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
UTC L2800 LINEAR INTEGRATED CIRCUIT
TYPICAL CHARACTERISTICS
Supply Voltage vs.Input Threshold Voltage
Supply Voltage vs.Supply Current
Ta=+25℃
Ta=+25℃
1.0
0.8
0.6
0.4
0.2
0
10
8
RB=390Ω
6
4
2
0
0
0
20
4
20
4
8
12
16
8
12
16
Supply voltage ,Vcc ( V )
Supply voltage ,Vcc ( V )
Ambient Temperaturevs. Input Threshold
VoltageVariationRatio
SupplyVoltagevs.InputThresholdVoltage
10
Vcc=2V
1.0
0.8
0.6
Ta=+25℃
5
0
0.4
0.2
0
-5
-10
0
1.0
2.0
3.0
4.0
5.0
-15
-40
Supply voltage ,Vcc ( V )
-20
0
20
40
60
80
100
Ambient temperature ,Ta (℃)
HighLevelOutput
LowLevelOutput
Vcc=2V
Ta=+25℃
RB=390Ω
Vcc=2V
Ta=+25℃
RB=390Ω
2.0
1.6
1.2
0.8
0.4
0
500
400
300
200
100
0
0
-10
-20
-30
-40
-50
0
80
20
40
60
100
High level output current ,IOUT(mA)
High level output current ,IOUT(mA)
5
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
UTC L2800 LINEAR INTEGRATED CIRCUIT
BR/CTL Pin Current vs. BR/CTL Pin Voltage
BR/CTL Pin Current vs. Output Source Current
-50
-40
-30
-20
-10
0
500
400
300
Vcc=2V
Ta=+25℃
Vcc=2V
VOUT=0.9V
Ta=+25℃
200
100
0
0
-0.8
-1.6
-2.0
-1.2
-1.6
-0.4
-0.8
-1.2
0
-0.4
-2.0
BR/CTL pin Current ,IBR (mA)
BR/CTL pin current ,IBR (mA)
BR/CTL Pin Current vs. SupplyCurrent
TimingResistorvs. OscillationFrequency
5.0
4.0
3.0
2.0
Vcc=2V
Ta=+25℃
1M
CT=100pF
Vcc=2V
Ta=+25℃
500k
200k
100k
CT=1000pF
50k
20k
10k
CT=10000pF
1.0
0
5k
2k
0
-20
BR/CTL pin current ,I BR (μA)
-100
-40
-80
-60
2k
5k
10k
20k
1k
Timing resistor ,RT (Ω)
SupplyVoltagevs.FrequencyVariationRatio
AmbientTemperaturevs.FrequencyVariationRatio
10
5
10
5
CT=270pF
Ta=+25℃
RT=3.0kΩ
Vcc=2V
CT=270pF
RT=3.0kΩ
0
0
-5
-5
-10
-15
-10
-15
0
2
8
12
14
16
100
4
6
10
-40
60
Ambient temperature ,Ta(℃)
-20
0
20
40
80
Supply voltage ,Vcc (V)
6
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
UTC L2800 LINEAR INTEGRATED CIRCUIT
OscillationFrequencyvs.MaximumDutyCycle
100
80
Vcc=2V
CT=270pF
Ta=+25℃
60
40
20
0
10K
100K
Oscillation frequency ,fosc (Hz)
1M
OutputPin Voltageand CurrentWaveforms(Reference Data)
Vcc=2V
CT=270pF
(V)
2V
6
4
2
0
RT=1.0kΩ
VOUT
(mA)
50
IOUT
0
-50
10mV
200ns
1.6
t
0
0.4
0.8
1.2
2.0
(μs)
Note:The OFF delay time of VOUT depends on
the characteristics of the external transistor.
Vcc
(5V)
22μH
18kΩ
UTC L2800
4
5
IOUT
VOUT
10μF
2kΩ
390Ω
-IN
Measurement Circuit Diagram
7
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
UTC L2800 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 1µA 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
SW
OFF
ON
MODE
Stand-by mode
Operating mode
BR/CTL
RB
SW
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”)
8
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
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
18kΩ
22μH
VO
5V
-IN
FB
1
8
OSC
GND
OUT
SCP
2
3
4
7
6
5
VIN
3V
Vcc
10μF
33μF
2kΩ
BR/CTL
390Ω
0.1μF
0.1μF
3kΩ
270pF
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.
9
UTC
UNISONIC TECHNOLOGIES CO., LTD.
QW-R103-030,A
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