PJ3800
Low Voltage Switching Regulator Controller
1-8
2003/04.rev.A
he PJ3800 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 1.8 V and
is ideal for the power supply of battery-operated electronic
equipment.
.
Wide supply voltage operating range: 1.8 to 15 V
Low current consumption: Typically 5.5 mA in
operation, 1 mA or less in stand-by
High speed operation is possible: Maximum 1 MHz
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.
Device Operation
Temperature Package
PJ3800CS
SOP-8
PJ3800CA
-20 ~ +85
TSSOP-8
T
FEATURES
ORDER INFORMATION
BLOCK DIAGRAM
Pin 1. Error amplifier inverting input
2. Soft Star & SCP
3. Power supply
4. Output current setting and control
5. Output
6. Ground
7. Oscillation frequency
8. Error amplifier output
SOP-8
TSSOP-8
PJ3800
Low Voltage Switching Regulator Controller
2-8
2003/04.rev.A
Rated Value
Parameter Symbol
Min. Max.
Unit
Power supply voltage
V
CC
-- 16 V
Output source current
I
O+
-- -50 mA
Output sink current
I
O-
-- 50 mA
Allowable dissipation
P
D
-- 570* mW
Operating temperature
T
op
-30 +85
Storage temperature
T
stg
-55 +125
* : When mounted on a 10 cm square double-sided epoxy board
WARNING: Semiconductor devices can be permanently damaged by application of stress (voltage, current, temperature, etc.)
in excess of absolute maximum ratings. Do not exceed these ratings.
Values
Parameter Symbol
Min. Typ. Max.
Unit
Power supply voltage
V
CC
1.8 -- 15 V
Error amplifier input voltage
V
I
0.2
--
1 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 3 10
k
Timing capacitance
C
T
100
270
10000
pF
Oscillation frequency
f
OSC
10 500
1000
kHz
Operating temperature
T
OP
30 +25 +85
WARNING: Recommended operating conditions are normal operating ranges for the semiconductor device. All the device's
electrical characteristics are warranted when operated within these ranges.
Always use semiconductor devices within the recommended operating conditions. Operation outside
these ranges may adversely affect reliability and could result in device failure.
No warranty is made with respect to uses, operating conditions, or combinations not represented on the data sheet.
Users considering application outside the listed conditions are advised to contact their Promax Johnton
representative beforehand.
ABSOLUTE MAXIMUM RATINGS
RECOMMENDED OPERATING CONDITIONS
PJ3800
Low Voltage Switching Regulator Controller
3-8
2003/04.rev.A
Value
Parameter Symbol
Condition
Min. Typ. Max.
Unit
Reset voltage
V
--
--
0.9
V
Circuit to prevent
malfunction at low
input voltage (U.V.L.O.) Threshold voltage
V
TH
--
1.1 1.3 1.5 V
Charging current
I
CS
VSCP
=
0
V
-0.5 -1.0 -0.7
A
Soft start
Voltage at soft start completion
V
tS
--
0.7 0.8 0.9 V
Charging current
I
CPC
VSCP
=
0
V
-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
f
OCS
R
T
=3.0k, C
T
= 270 pF
400 500 600
kHz
Frequency input stability
f
dV
VCC = 2 V to 15 V
--
2
10
%
Saw tooth wave
oscillator (OSC)
Frequency variation with
temperature
f
dT
Ta =-20 to +85
-- 5 --
%
Input threshold voltage
V
T
V
FB
= 450 mV
480
500
520
mV
VT input stability
V
TdV
V
CC
= 2 V to 15 V
--
5
20
mV
VT variation with temperature
V
TdT
Ta =-20 to +85
-- 1 --
%
Input bias current
I
B
V
IN
= 0 V
-1.0
-0.2
1.0
A
Voltage gain
A
V
-- 70
100
145
V/V
Frequency bandwidth
BW
AV = 0 dB
--
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
-
VFB = 0.45 V
24 40 --
A
Idle period
adjustment section
Maximum duty cycle
t
DUTY
R
T
=3.0k,C
T
=270pF
VFB =0.8V
65 75 85 %
V
OH1
R
B
= 390I
O
=-15mA
1.0 1.2 -- V
V
OH2
R
B
=750,V
CC
=1.8V
I
O
= -10mA
0.8 1 -- V
V
OL1
R
B
= 390,I
O
=15mA
-- 0.1 0.2 V
Output voltage
V
OL2
R
B
= 750 V
CC
=1.8V
I
O
= 10mA
-- 0.1 0.2 V
Output source current
I
O+
R
B
= 390 V
O
= 0.9V
-- -30 -20
mA
Output sink current
I
O-
R
B
= 390 V
O
= 0.3V
30 60 --
mA
Output section
Pull down resistance
R
O
-- 20
30
40
k
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 V
CC
-- -- 1
A
Entire device
Average supply current
t
I
CC
R
B
= 390
-- 5.5 9.3
mA
ELECTRICAL CHARACTERISTICS
(
VCC = +2 V, Ta = +25 C)
PJ3800
Low Voltage Switching Regulator Controller
4-8
2003/04.rev.A
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 saw tooth 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 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
t
PE
[s]
0.8 C
PE
[F]
DIAGRAM
HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION
PJ3800
Low Voltage Switching Regulator Controller
5-8
2003/04.rev.A
TYPICAL CHARACTERISTICS
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