UTC L2800 Switching regulator controller(low voltage) Datasheet

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
*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
UTC
-IN
1
8
FB
SCP
2
7
OSC
Vcc
3
6
GND
BR/CTL
4
5
OUT
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UTC L2800
LINEAR INTEGRATED CIRCUIT
PIN DESCRIPTION
PIN NO.
SYMBOL
I/O
1
2
3
4
5
6
7
8
-IN
SCP
VCC
BR/CTL
OUT
GND
OSC
FB
I
I
O
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
Capacitor and resistor connection pin for setting the oscillation frequency
Error amplifier output pin
BLOCK DIAGRAM
Vcc
OSC
3
7
Reference
voltage supply
Sawtooth
wave oscillator
0.6V
0.1V
1.25V
-IN
1
-
Error Amp.
0.5V
FB
+
+
+
36kΩ
+
5
0.1V
500Ω
30kΩ
PWM
Comp.
Output drive
control circuit
0.3V
DTC 0.6V
8
OUT
Soft start
SCP
6
2
GND
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
RATINGS
UNIT
Vcc
IO+
IO-
16
-50
50
V
mA
mA
PD
570*
580*
-55 ~ +125
-30 ~ +85
mW
Storage Temperature
Tstg
Operating Temperature
Top
* When mounted on a 10cm square double-sided epoxy board.
UTC
°C
°C
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UTC L2800
LINEAR INTEGRATED CIRCUIT
RECOMMENDED OPERATING CONDITIONS (Ta=25°C)
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
MIN
Vcc
VI
VBR
IO+
IOCPE
CP
RB
RT
CT
fosc
Top
1.8
-0.2
-0.2
-40
TYP
MAX
UNIT
15
1.0
Vcc
V
V
V
mA
mA
µF
µF
Ω
kΩ
pF
kHz
°C
40
150
1.0
100
10
-30
0.1
0.1
390
3.0
270
500
+25
5000
10.0
10000
1000
+85
ELECTRICAL CHARACTERISTICS (Ta=25°C, 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
SYMBOL
Ics
UTC
VSCP=0V
Vts
Icpc
VtPC
fosc
TYP MAX UNIT
VSCP=0V
RT=3.0kΩ, CT=270pF
0.9
V
1.1
1.3
1.5
V
-1.5
-1.0
-0.7
µA
0.7
0.8
0.9
V
-1.5
0.7
400
-1.0
0.8
500
-0.7
0.9
600
µA
V
kHz
2
10
%
520
20
mV
mV
µA
V/V
MHz
V
V
µA
µA
fdV
Vcc=2V ~ 15V
fdT
Ta=-30°C ~ +85°C
VT
VTdV
VFB=450mV
Vcc=2V ~ 15V
Ta=-30°C ~ +85°C
480
500
5
VIN=0V
-1.0
70
-0.2
100
6
0.87
0.05
-40
40
1.0
145
85
VTdT
IB
Av
BW
VOM+
VOMIOM+
IOMtDUTY
VOH1
VOL1
VOL2
Output Source Current
Output Sink Current
Pull Down Resistance
MIN
VR
VTH
VOH2
Output Voltage
TEST CONDITIONS
IO+
IORO
5
1
AV=0dB
0.78
VFB=0.45V
24
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
%
65
75
1.0
1.2
0.8
1.0
0.1
30
20
%
0.2
-24
%
V
V
0.2
V
0.1
0.2
V
-30
60
30
-20
mA
mA
kΩ
40
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LINEAR INTEGRATED CIRCUIT
PARAMETER
SYMBOL
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
VBR
IOFF
ION
IBR
ICCS
ICC
TEST CONDITIONS
RB=390Ω
MIN
0.2
-20
TYP MAX UNIT
0.3
0.4
0
-45
-0.1
1
9.3
-1.8
BR/CTL pin open or Vcc
RB=390Ω
5.5
V
µA
µA
mA
µA
mA
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[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]
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LINEAR INTEGRATED CIRCUIT
TYPICAL CHARACTERISTICS
Supply Voltage vs.Input Threshold Voltage
Supply Voltage vs.Supply Current
Ta=+25℃
RB=390Ω
Input threshold Voltage ,VT (V)
Supply current ,Icc (mA)
10
8
6
4
2
0
0
4
8
12
Supply voltage ,Vcc ( V )
16
Input threshold voltage variation ration
,ΔVT/VT (%)
Input threshold voltage ,VT (V)
Ta=+25℃
0.6
0.4
0.2
0
1.0
2.0
3.0
4.0
Supply voltage ,Vcc ( V )
0.4
0.2
0
5
0
-5
-10
5.0
-15
-40
Low level output voltage ,VOUT (mV)
Low level output voltage ,VOUT (V)
1.2
0.8
0.4
0
0
-10
-20
-30
-40
High level output current ,IOUT(mA)
UTC
-20
0
20
40
60
Ambient temperature ,Ta (℃)
80
100
Low Level Output
Vcc=2V
Ta=+25℃
RB=390Ω
1.6
20
8
12
16
Supply voltage ,Vcc ( V )
Vcc=2V
High Level Output
2.0
4
10
0.8
0
0.6
Ambient Temperature vs. Input Threshold
Voltage Variation Ratio
Supply Voltage vs.Input Threshold Voltage
1.0
0.8
0
20
Ta=+25℃
1.0
-50
Vcc=2V
Ta=+25℃
RB=390Ω
500
400
300
200
100
0
0
80
20
40
60
High level output current ,IOUT(mA)
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LINEAR INTEGRATED CIRCUIT
BR/CTL Pin Current vs. BR/CTL Pin Voltage
-50
500
BR/CTL pin voltage ,VBR (mV)
Output source current ,IOUT (mA)
BR/CTL Pin Current vs. Output Source Current
-40
Vcc=2V
VOUT=0.9V
Ta=+25℃
-30
-20
-10
0
0
-0.4
-0.8
-1.2
-1.6
300
200
100
0
-2.0
Vcc=2V
Ta=+25℃
400
0
Oscillation frequency ,fosc (Hz)
Supply current ,I CC (mA)
1M
3.0
2.0
1.0
0
-20
0
-100
-40
-80
-60
BR/CTL pin current ,I BR (μA)
CT=100pF
Vcc=2V
Ta=+25℃
500k
200k
CT=1000pF
100k
50k
20k
CT=10000pF
10k
5k
1k
Supply Voltage vs. Frequency Variation Ratio
20k
2k
5k
10k
Timing resistor ,R T (Ω)
Ambient Temperature vs. Frequency Variation Ratio
10
CT=270pF
Ta=+25℃
RT=3.0kΩ
5
Frequency variation ratio ,Δf/f (%)
Frequency variation ratio ,Δf/f (%)
-2.0
2k
10
0
-5
-10
-15
-1.6
Timing Resistor vs. Oscillation Frequency
Vcc=2V
Ta=+25℃
4.0
-1.2
BR/CTL pin current ,I BR (mA)
BR/CTL Pin Current vs. Supply Current
5.0
-0.8
-0.4
BR/CTL pin Current ,I BR (mA)
0
2
UTC
8
4
6
10
Supply voltage ,Vcc (V)
12
14
16
Vcc=2V
CT=270pF
RT=3.0kΩ
5
0
-5
-10
-15
-40
-20
60
0
20
40
Ambient temperature ,Ta (℃)
80
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UTC L2800
LINEAR INTEGRATED CIRCUIT
Oscillation Frequency vs.Maximum Duty Cycle
Maximum duty cycle, tDUTY (%)
100
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
Vcc=2V
CT=270pF
RT=1.0kΩ
2V
4
VOUT
2
0
(mA)
50
IOUT
0
-50
10mV
200ns
0.4
0
0.8
1.2
1.6
2.0
t
(μs)
Note:The OFF delay time of VOUT depends on
the characteristics of the external transistor.
Vcc
(5V)
22μH
18kΩ
UTC L2800 5
IOUT
4
VOUT
10μF
2kΩ
390Ω
-IN
Measurement Circuit Diagram
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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
SW
MODE
OFF
ON
Stand-by mode
Operating mode
4
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”)
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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
18kΩ
22μH
-IN
VIN
3V
SCP
Vcc
33μF
2kΩ
BR/CTL
0.1μF
1
8
2
7
3
6
4
5
VO
5V
FB
OSC
GND
10μF
OUT
390Ω
270pF
3kΩ 0.1μF
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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