UTC L2800 LINEAR INTEGRATED CIRCUIT
UTC
UNISONIC TECHNOLOGIES CO., LTD.
1
QW-R121-010,A
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.
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.
SOP-8
TSSOP-8
PIN CONFIGURATION
-IN
1
2
3
4
8
7
6
SCP
Vcc
5
BR/CTL
FB
OSC
GND
OUT
UTC L2800 LINEAR INTEGRATED CIRCUIT
UTC
UNISONIC TECHNOLOGIES CO., LTD.
2
QW-R121-010,A
PIN DESCRIPTION
PIN NO.
SYMBOL
I/O
DESCRIPTION
1
-IN
I
Error amplifier inverting input pin
2
SCP
-
Soft start and SCP setting capacitor connection pin
3
VCC
-
Power supply pin
4
BR/CTL
I
Output current setting and control pin
5
OUT
O
Totem-pole type output pin
6 GND -
Ground
pin
7
OSC
-
Capacitor and resistor connection pin for setting the oscillation frequency
8
FB
O
Error amplifier output pin
BLOCK DIAGRAM
500
36k
3
7
1
8
6
2
4
5
Reference
voltage supply
Sawtooth
wave oscillator
Output drive
control circuit
Soft start
SCP
30k
BR/CTL
SCP
GND
FB
-IN
Vcc
OSC
OUT
0.3V
DTC 0.6V
PWM
Comp.
0.1V
0.5V
Error Amp.
1.25V
0.6V
0.1V
-
+
-
+
+
+
ABSOLUTE MAXIMUM RATINGS
(Ta=25)
PARAMETER SYMBOL
RATINGS
UNIT
Power Supply Voltage
Vcc
16
V
Output Source Current
I
O
+
-50
mA
Output Sink Current
I
O
-
50
mA
Power Dissipation
SOP-8
TSSOP-8
P
D
570*
580*
mW
Storage Temperature
Tstg
-55 ~ +125
C
Operating Temperature
Top
-30 ~ +85
C
* When mounted on a 10cm square double-sided epoxy board.
UTC L2800 LINEAR INTEGRATED CIRCUIT
UTC
UNISONIC TECHNOLOGIES CO., LTD.
3
QW-R121-010,A
RECOMMENDED OPERATING CONDITIONS
(Ta=25
C)
PARAMETER SYMBOL
MIN
TYP
MAX
UNIT
Power Supply Voltage
Vcc
1.8
15
V
Error Amplifier Input Voltage
V
I
-0.2 1.0 V
BR/CTL Pin Input Voltage
V
BR
-0.2 Vcc V
Output Source Current
I
O
+
-40 mA
Output Sink Current
I
O
-
40
mA
SCP Pin Capacitance
C
PE
0.1
F
Phase Compensation Capacitance
C
P
0.1
F
Output Current Setting Resistance
R
B
150
390
5000
Timing Resistance
R
T
1.0
3.0
10.0
k
Timing Capacitance
C
T
100
270
10000
pF
Oscillation Frequency
fosc
10
500
1000
kHz
Operating Temperature
Top
-30
+25
+85
C
ELECTRICAL CHARACTERISTICS
(Ta=25
C, V
CC
=+2V)
PARAMETER SYMBOL
TEST
CONDITIONS
MIN
TYP
MAX
UNIT
Reset Voltage
V
R
0.9
V
Circuit to prevent
malfuncition at low input
oltage (U.V.L.O)
Threshold Voltage
V
TH
1.1
1.3 1.5 V
Charging Current
Ics
V
SCP
=0V -1.5
-1.0
-0.7
A
Soft Start
Voltage at soft start
completion
Vts
0.7
0.8
0.9
V
Charging Current
Icpc
V
SCP
=0V -1.5
-1.0
-0.7
A
Short Circuit
Detection(S.C.P.)
Threshold Voltage
V
tPC
0.7
0.8
0.9
V
Oscillation Frequency
fosc
R
T
=3.0k
, C
T
=270pF
400
500 600 kHz
Frequency Input
Stability
f
dV
Vcc=2V ~ 15V
2
10
%
Sawtooth Wave
Oscillator(OSC)
Frequency Variation
With Temperature
f
dT
Ta=-30
C ~ +85C
5 %
Input Threshold Voltage
V
T
V
FB
=450mV 480
500
520
mV
V
T
Input Stability
V
TdV
Vcc=2V ~ 15V
5
20
mV
V
T
Variation With
Temperature
V
TdT
Ta=-30
C ~ +85C
1 %
Input Bias Current
I
B
V
IN
=0V -1.0
-0.2
1.0
A
Voltage Gain
Av
70
100 145
V/V
Frequency Bandwidth
BW
A
V
=0dB
6
MHz
V
OM
+
0.78
0.87
V
Maximum Output
Voltage Range
V
OM
-
0.05
0.2 V
Output Source Current
I
OM
+
-40
-24
A
Error Amplifier
Output Sink Current
I
OM
-
V
FB
=0.45V
24
40
A
Idle Period Adjustment
Section
Maximum Duty Cycle
t
DUTY
R
T
=3.0k
, C
T
=270pF
V
FB
=0.8V
65
75 85 %
V
OH1
R
B
=390
, Io=-15mA
1.0
1.2 V
V
OH2
R
B
=750
, Vcc=1.8V
Io= -10mA
0.8
1.0 V
V
OL1
R
B
=390
, Io=15mA
0.1
0.2 V
Output Voltage
V
OL2
R
B
=750
, Vcc=1.8V
Io=10mA
0.1
0.2 V
Output Source Current
I
O
+
R
B
=390
, Vo=0.9V
-30
-20
mA
Output Sink Current
I
O
-
R
B
=390
, Vo=0.3V
30
60 mA
Output Section
Pull Down Resistance
R
O
20
30
40
k
UTC L2800 LINEAR INTEGRATED CIRCUIT
UTC
UNISONIC TECHNOLOGIES CO., LTD.
4
QW-R121-010,A
PARAMETER SYMBOL
TEST
CONDITIONS
MIN
TYP
MAX
UNIT
Pin Voltage
V
BR
R
B
=390
0.2
0.3 0.4 V
Input Off Condition
I
OFF
-20
0
A
Input On Condition
I
ON
-45
A
Output Current Setting
Section/Control Section
Pin Current Range
I
BR
-1.8
-0.1
mA
Stand-by Current
I
CCS
BR/CTL pin open or Vcc
1
A
Entire Device
Average Supply Current
I
CC
R
B
=390
5.5
9.3
mA
DIAGRAM
FB pin voltage
Reference input for short
circuit detection comparator
Idle period setting voltage
Soft start setting voltage
Sawtooth wave output
OUT pin waveforms
SCP pin waveforms
OFF
ON
Power supply control SW
Soft start
ts
Output
short
circuit
tPE
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 C
PE
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*C
PE
[
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 C
PE
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
t
PE
[S]0.8*C
PE
[
F]
UTC L2800 LINEAR INTEGRATED CIRCUIT
UTC
UNISONIC TECHNOLOGIES CO., LTD.
5
QW-R121-010,A
TYPICAL CHARACTERISTICS
Supply Voltage vs.Supply Current
0
2
4
6
4
0
8
12
16
20
8
10
Supply voltage ,Vcc ( V )
Suppl
y cur
r
ent ,Icc (
m
A)
-40
-10
-20
-5
0
0
-15
20
40
60
80
100
5
10
Supply Voltage vs.Input Threshold Voltage
0
0.2
0.4
0.6
4
0
8
12
16
20
0.8
1.0
Supply voltage ,Vcc ( V )
Supply Voltage vs.Input Threshold Voltage
0
0.2
0.4
0.6
1.0
0
2.0
3.0
4.0
5.0
0.8
1.0
Supply voltage ,Vcc ( V )
Ambient Temperature vs. Input Threshold
Voltage Variation Ratio
High Level Output
0
0.4
0.8
1.2
-10
0
-20
-30
-40
-50
1.6
2.0
Low Level Output
0
100
200
300
20
0
40
60
80
100
400
500
Low
level out
put
volt
age ,
V
OUT
(m
V
)
I
nput
t
h
reshold V
o
lt
age
,
V
T
(V
)
I
nput
t
h
reshold volt
age
,
V
T
(V
)
Ambient temperature ,Ta ( )
High level output current ,I
OUT
(mA)
Ta=+25
R
B
=390
Ta=+25
Ta=+25
Vcc=2V
Vcc=2V
Ta=+25
R
B
=390
Vcc=2V
Ta=+25
R
B
=390
Input thr
e
shol
d vol
t
age var
i
ati
on r
a
ti
on
,
VT
/V
T
(
%
)
High level output current ,I
OUT
(mA)
Low level
out
put
volt
age
,
V
OUT
(V
)
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