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Bay Linear
Inspire the Linear Power
Switching Regulator Controller Step Up Low Voltage (BIPOLAR)
B3800
Description
The Bay Linear B3800 series is monolithic control circuit containing the primary functions required for DC-to-DC converters. This device is design for low voltage applications incorporating a soft start function and sort 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 equipments. This series was specially designed to be incorporated in StepDown and voltage-inverting applications with a minimum number of external components. The B3800 is offer in 8-pin DIP or Surface mount package.
Features
* * * * * * * * * *
* * Wide operation from............... 1.8 to 15V Low Standby Current.................... 1 A Low Current Consumption......... 5.5mA high Speed Operation ................ 1MHz Incorporates soft start circuit Incorporates a stand-by function Incorporate a times-latch short circuit detection circuit (SCP) Totem-pole type output with adjustable on/off current (for NPN transistor) The error amplifier gain is set inside the IC, so peripheral components are minimized. Direct Replacement for MB3800 Digital Camera MP3 Low Battery Operating Applications
Applications
*
Pin Connection
Ordering Information
SO-8 8-pin
B3800M
P-DIP 8-pin
B3800P
Operating Temp. Range
-40C to 85C
88-Pin Surface Mount
-IN SCP Vcc BR/CTL 1 2 3 4 8 7 6 5 FB OSC GND OUT
Top View
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
PIN Description
Pin No. Symbol I/O
1 2 3 4 5 6 7 8
-IN SCP VCC BR/CTL VOUT GND OSC FB
I I O O
Description Error amplifier inverting 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 setting the oscillation frequency Error amplifier output pin
Absolute Maximum Rating
Parameter
Supply Voltage Output source current Output sink current Allowable dissipation
Symbol
Value
Unit
VCC 16 V IO+ -50 mA IO50 mA 570 mW SOP-8, Ta+25C 430 mW SOP-8, Ta+25C 580 mW SSOP-8, Ta+25C Operating temperature Top -30 to +85 C Storage temperature Tstg -55 to +125 C 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.
Recommended Operating Condition
Parameter Symbol Min Values Typ. Max. Unit
Power Supply Voltage VCC 1.8 15 V Error amplifier input voltage VI -.0.2 1.0 V BR/CTL pin input voltage VBR -0.2 VCC V Output source current IO+ -40 mA Output sink current IO40 mA SCP pin capacitance CPE 0.1 F Phase compensation capacitance CP 0.1 F Output current setting resistance RB 150 390 5000 Timing resistance RT 1.0 3.0 10.0 k Timing Capacitance CT 100 270 10000 pF Oscillation frequency fOSC 10 500 1000 kHz Operation temperature -30 +30 +85 TOP C 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 Bay Linear.
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
Electrical Characteristics
Parameter
Circuit to Prevent Malfunction at low input voltage (U.V.L.O.) Soft Start Short Circuit detection (OSC) Sawtooth wave oscillator (OSC) Reset Voltage Threshold voltage Changing current Voltage at soft start completion Charging current Threshold voltage Oscillation freq. Frequency input stability Frequency variation with temperature Input threshold voltage VTinput stability VT variation with temperature Input bias current Voltage gain Frequency bandwidth Maximum output voltage range Output source current Output sink current Maximum duty cycle
Symbol
VR VTH ICS VTS Icpc VPC focs fdv fdt VT VTdv VTDT IB AV BW VOM VOMIOM+ IOM_ VOH1
+
Conditions
-
Min.
1.1 -1.5
Value Typ.
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 -30 60 30 0.3 5.5
Max.
0.9 1.5 -0.7 0.9 -0.7 0.9 600 10 520 20 1.0 145 0.2 -24 85 0.2 0.2 -20 40 0.4 0 -45 -0.1 1 9.3
Unit
V V A V A V kH z % % mV mV % A V/ V M Hz V A A % V V V V mA mA k V A A mA mA mA
VSCP=0V VSCP=0V -
0.7 -1.5 0.7 400 480 -1.0 70 0.78 24 65 1.0 0.8 30 20 0.2 -20 -1.8 -
RT=3.0k, CT=270pF VCC=2V to 15V Ta=-30C to +85C VFB=450mV VCC= 2V to 15V Ta= -30C to +85C VIN=0V
Error amplifier
AV=0dB
VFB=0.45V RT=3.0k, CT=270pF VFB=0.8V RB=390, IO= -15mA RB=750, IO= -10mA, VCC=1.8V RB=390, IO=15mA RB=750, IO=10mA, VCC=1.8V RB=390, VCC=0.9V RB=390, VCC=0.3V RB=390, BR/CTL pin open or Vcc RB=390,
Idle period adjustable section
tDUTY VOH2 VOL1 VOL2 IO+ IORO VBR IOFF ION IBR ICCB ICC
Output voltage Output section Output source current Output sink current Pull down resistance Pin Voltage Input off condition Input on condition Pin current range Stand-by current Entire device Average supply current
Output current setting section/ Control section
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
TIMMING DIAGRAM
BLOCK DIAGRAM
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
Typical Characteristics
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
Typical Characteristics (continued)
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
Typical Characteristics (continued)
Bay Linear B3800
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
Application Descriptions
Power Supply Control Function
Stand- by mode (supply current 1 mA or less) can be set by connecting the BR/ CTL pin (pin 4) to VCC or by making the pin open circuit. 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). Other Functions Soft start and short circuit detection Soft start operation is set by connecting capacitor CPE to the 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 0.8 V, 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 "n HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION".) 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.
Switching Regulator Function
Reference voltage circuit The reference voltage circuit generates a temperaturecompensated reference voltage (@1.25V) from voltage supplied from the power supply pin (pin 3). In addition to providing the reference voltage for the switching regulator, the circuit also sets the idle period. 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). 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. PWM comparator (PWM Comp.) The voltage comparator has one inverting and three noninverting 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.
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
HOW TO SET THE TIME CONSTANT FOR SOFT START AND SHORT CIRCUIT DETECTION 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 [mF]
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 [mF]
APPLICATION DIAGRAM
B3800
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com
B3800
8 pin SOIC
4.0 (0.158) 3.8 (0.150)
5.2 (0.205) 4.6 (0.181)
6.2 (0.244) 5.8 (0.228)
Pin 1
1.27 (0.50) BSC
1.75 (0.069) 1.35 (0.053) 0.78 (0.031) 0.61 (0.024) 5.0 (0.197) 4.8 (0.188) 0.37 (0.015) BSC 0.77 (0.030) 0.64 (0.025) 7 (4 PLCS)
45
3 -6 0.56 (0.022) 0.49 (0.019) 0.45 (0.018) 0.35 (0.014) 0.20 (0.008) 0.10 (0.004) 0.22 (0.009) 0.19 (0.007) 7 (4 PLCS)
Advance Information- These data sheets contain descriptions of products that are in development. The specifications are based on the engineering calculations, computer simulations and/ or initial prototype evaluation. Preliminary Information- These data sheets contain minimum and maximum specifications that are based on the initial device characterizations. These limits are subject to change upon the completion of the full characterization over the specified temperature and supply voltage ranges.
The application circuit examples are only to explain the representative applications of the devices and are not intended to guarantee any circuit design or permit any industrial property right to other rights to execute. Bay Linear takes no responsibility for any problems related to any industrial property right resulting from the use of the contents shown in the data book. Typical parameters can and do vary in different applications. Customer's technical experts must validate all operating parameters including " Typical" for each customer application.
LIFE SUPPORT AND NUCLEAR POLICY Bay Linear products are not authorized for and should not be used within life support systems which are intended for surgical implants into the body to support or sustain life, in aircraft, space equipment, submarine, or nuclear facility applications without the specific written consent of Bay Linear President.
Bay Linear, Inc
2418 Armstrong Street, Livermore, CA 94550 Tel: (925) 606-5950, Fax: (925) 940-9556
www.baylinear.com

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