Fairchild Semiconductor ML4854 Datasheet
www.fairchildsemi.com
ML4854
Adjustable, Low-Current, 2-Cell Boost Regulator
with Shutdown and Low Battery Detect
Features
• 95% Efficiency at 200mA Load Current
• Integrated Peak Current Limit
• Variable Output Voltage Determined by External Resistors
• Variable On-time Pulse Frequency Modulation (PFM)
• Fully Internal Synchronous Rectifier (no external diodes)
for High Efficiency and Low Peak Currents
• Low-Battery Detection
• Logic Controlled Shutdown with True Load Disconnect
Applications
• 2-3 alkaline/NiMH cells or 1 Li-Ion cell Operated Devices
• Cell Phones
• Medical Devices
•PDAs
• Portable Instrumentation
Typical Application
Input 1.6V
to 4.5V
ML4854
V
1
On
Off
Low Battery
Detect In
Low Battery
Detect Out
2
3
4
IN
SHDN
LBI
LB0
General Description
The ML4854 is a low power boost regulator designed for
low voltage DC to DC conversion in two-cell battery powered systems such as cell phones and PDAs. The converter
starts up at 1.3V and has an operating input voltage range
from 1.6V to 4.5V. After the start it operates at an input
voltage as low as 0.8V. Output voltage can be adjusted by
external resistors from 3.3V to 5V with a maximum load
current of 0.5A.
Quiescent current in shut down mode is less than 30µA,
which maximizes the battery live time. The ON time changes
with the input voltage to maintain the ripple current constant
and to provide the highest efficiency over a wide load range,
while maintaining low peak currents in the boost inductor.
The combination of integrated synchronous rectification,
variable frequency operation, and low supply current make
ML4854 ideal for portable applications.
The ML4854 is available in an 8 lead TSSOP package.
GND
8
7
V
L
6
V
OUT
5
FB
Output 3.3V to 5V
up to 0.5A
REV. 1.0.7 5/6/03
PRODUCT SPECIFICATION ML4854
Pin Configuration
8-Lead TSSOP (T08)
V
SHDN
LBI
LB0
IN
1
2
3
4
TOP VIEW
Pin Description
PIN NAME FUNCTION
1 V
2 SHDN Shut Down . Pulling this pin low shuts down the regulator, isolating the load from the input.
3 LBI Low-Battery Input . Pulling this pin below a threshold causes the LBO pin to go low.
4 LBO Low-Battery Output . This pin provides an active low signal to alert the user when the LBI
5FB Programming Feedback Pin . Sets the output voltage. This pin is used to adjust the output
6V
OUT
7V
8 GND Ground of the IC .
Battery Input Voltage . Supplies the IC during start-up. After the output is running, the IC draws
IN
power from V
OUT
.
voltage falls below its targeted value. The open-drain output can be used to reset a
microcontroller.
voltage via a resistive divider from V
OUT
Boost regulator output . Output voltage can be set to be in the 3 to 5V range. Startup at
moderate load is achievable at input voltages around 1.25V.
Boost inductor connection . An inductor is connected between this pin and V
L
the output supply, this pin pulls low, charging the inductor, then shuts off dumping the energy
through the synchronous rectifier to the output.
8
7
6
5
GND
V
L
V
OUT
FB
.
. When servicing
IN
Absolute Maximum Ratings
Absolute maximum ratings are those values, beyond which the device could be permanently damaged. Absolute maximum
ratings are stress ratings only and functional device operation is not implied.
Parameter Min. Max. Units
,
V
V
IN
Switch Voltage (V
Voltage on any other Pin -0.3 V
Peak Switch Current (Ipeak) — Internally Limited —
Output Current (I
Continuous Power Dissipation 320 mW
Thermal Resistance ( θ
Junction Temperature 150 °C
Storage Temperature Range -65 +165 °C
Lead Temperature (soldering, 10s) 300 °C
2
Voltages (Relative to GND) -0.3 7 V
OUT
to GND) -0.3 V
L
) 500 mA
OUT
) 124 °C/W
JA
OUT
OUT
+0.3
+0.3
V
V
REV. 1.0.7 5/6/03
µ
µ
µ
µ
µ
µ
µ
ML4854 PRODUCT SPECIFICATION
Recommended Operating Conditions
Parameter Min. Max. Units
Temperature Range -40 +85 °C
Operating Range
V
IN
Operating Range
V
OUT
1.6 0.9 V
OUT
3.0 5.0 V
V
Electrical Characteristics
Unless otherwise specified, V
at T
= +25°C
A
Parameter Conditions Min. Typ. Max. Units
Start Up Voltage I
Operating Voltage After start I
Output Voltage V
Output Voltage Adjust Range 3 5 V
Steady State Output Current
(see diagram)
Pulse Width V
Minimum Off-Time 0.5
Line Regulation V
Load Regulation 0 to 250mA V
Feedback Voltage (VFB) 1.230 V
LBI Threshold Voltage 0.390 V
LBI Hysteresys 25 mV
Internal NFET, PFET ON Resist. I
Efficiency (I
Quiescent Current – SHDN SHDN=0V, R1 excluded,V
LBO Output Voltage V
SHDN Input Voltage @V
SHDN Input Voltage @V
=1.6V to 3V, I
IN
=3V V
IN
=1.6V V
IN
=1mA, T
LOAD
<1mA 1.25 1.5 V
LOAD
LOAD
(nom.)=3.3V
OUT
V
(nom.)=5V
OUT
V
=3.3V, V
OUT
V
=5V, V
OUT
= 3V 0.8 1.32 1.9
IN
V
= 2.4V 1.2 1.64 2.3
IN
V
= 1.8V 1.8 2.15 3.1
IN
V
= 1.5V 2.2 2.57 4.0
IN
=1.6V to 3V, I
IN
V
=5V 0.5 %
OUT
0 to 150mA V
= 100mA 275 m Ω
LOAD
=200mA) V
LOAD
IN
=2.5V 330 mA
IN
IN
IN
SHDN=3V, R1 excluded,V
= 0, I
LBI
=3.3V/5V 1.6 V
OUT
=3.3V/5V 0.8 V
OUT
=1mA 0.2 V
SINK
=-40°C to +85°C. Test Circuit Fig.1. Typical values are
A
=10mA, V
=3.3V/5V 0.8 V
OUT
3.15
4.775
3.3
5
=2.5V 500 mA
=2mA, V
OUT
=2.4V ,V
=2.4V ,V
=3V, V
IN
OUT
OUT
=3.3V 0.5 %
OUT
=3.3V 1.0 %
=5V 1.0 %
= 3.3V 95 %
OUT
=3V 26 100
IN
=3V 85 200
IN
3.45
5.225
V
V
s
s
s
s
s
A
A
REV. 1.0.7 5/6/03
3
PRODUCT SPECIFICATION ML4854
UP1B
L1
10uH
ML4854
100
Gnd
Vout
VL
FB
8
7
6
JP1
R6
287K
C3
18pF
C4
1.
0uF
R4
402K
R5
240K
J1
SCOPE JACK
+
C2
47uF
10V
VOUT
1
2
3.3V to 5.0V
C5
1uF
0.
GND1
1
2
VIN
2
1
1.6V to 3.0V
SHDN
2
1
Reset
2
1
Ext
Pull Up
2
1
GND
2
1
+
C1
47µF
R1
750K
R2
240K
JP2
JP3
U1
1
2
3
4 5
R3
100K
Vin
Shut down
LBI
LBO
Figure 1. Test Circuit
4
REV. 1.0.7 5/6/03
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