Micro Linear Corporation ML4851IS-3, ML4851IS-5, ML4851ES-3, ML4851CS-3, ML4851CS-5 Datasheet

FEATURING

Extended Commercial Temperature Range

for Portable Handheld Equipment

-20˚C to 70˚C

ML4851*

Low Current, Voltage Boost Regulator

GENERAL DESCRIPTION

The ML4851 is a low power boost regulator designed for

FEATURES

n Guaranteed full load start-up and operation at 1V input

DC to DC conversion in 1 to 3 cell battery powered
systems. The maximum switching frequency can exceed

n Maximum switching frequency > 100kHz

100kHz, allowing the use of small, low cost inductors.

n Pulse Frequency Modulation (PFM) and internal

The combination of BiCMOS process technology, internal
synchronous rectification, variable frequency operation,
and low supply current make the ML4851 ideal for 1 cell
applications. The ML4851 is capable of start-up with input
voltages as low as 1V and is available in 5V and 3.3V
output versions with output voltage accuracy of ±3%.

synchronous rectification for high efficiency

n Minimum external components

n Low ON resistance internal switching FETs

n Micropower operation

An integrated synchronous rectifier eliminates the need
for an external Schottky diode and provides a lower
forward voltage drop, resulting in higher conversion
efficiency. In addition, low quiescent battery current and
variable frequency operation result in high efficiency
even at light loads. The ML4851 requires only one
inductor and two capacitors to build a very small
regulator circuit capable of achieving conversion
efficiencies in excess of 90%.

The circuit also contains a RESET output which goes low
when the IC can no longer function due to low input
voltage, or when the DETECT input drops below 200mV. *Some Packages Are Obsolete

n 5V and 3.3V output versions

BLOCK DIAGRAM

DETECT

4

V

IN

1

V

REF

SRQ

+

COMP

–

START-UP

Q

REFERENCE

GND

3

RESET

ONE SHOT

V

REF

5µs

7

2

6

V

L

V

OUT

+
–

–
+

V

REF

V

REF

5

PWR

GND

8

July, 2000

DATASHEET

1

ML4851

PIN CONFIGURATION

PIN DESCRIPTION

8-Pin SOIC (S08)

V

IN

V

REF

GND

DETECT

ML4851

1

2

3

4

TOP VIEW

8

7

6

5

PWR GND

RESET

V

L

V

OUT

PIN NAME FUNCTION

1V

2V

IN

REF

Battery input voltage

200mV reference output

3 GND Analog signal ground

4 DETECT Pulling this pin below V

RESET pin to go low

causes the

REF

PIN NAME FUNCTION

5V

6V

OUT

L

Boost regulator output

Boost inductor connection

7 RESET Output goes low when regulation

cannot be achieved, or when DETECT
goes below V

REF

8 PWR GND Return for the NMOS output transistor

2

July, 2000

DATASHEET

ML4851

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.

V

.......................................................................... 7V

OUT

Voltage on any other pin .....GND – 0.3V to V

Peak Switch Current, I
Average Switch Current, I

...................................................1A

(PEAK)

..................................... 250mA

(AVG)

OUT

+ 0.3V

OPERATING CONDITIONS

Temperature Range

ML4851CS-X.............................................. 0ºC to 70ºC

ML4851ES-X ........................................... –20ºC to 70ºC

V

Operating Range

IN

ML4851CS-X................................ 1.0V to V

ML4851ES-X ................................ 1.1V to V

Thermal Resistance (qJA).................................... 160ºC/W

OUT
OUT

– 0.2V
– 0.2V

Junction Temperature .............................................. 150ºC

Storage Temperature Range ...................... –65ºC to 150ºC

Lead Temperature (Soldering 10 sec.) ..................... 260ºC

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, V

SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS

SUPPLY

I

I

OUT(Q)VOUT

REFERENCE

VIN Current VIN = V

IN

Quiescent Current 8 10 µA

I

VL Quiescent Current 1µA

L

= Operating Voltage Range, TA = Operating Temperature Range (Note 1)

IN

– 0.2V 50 60 µA

OUT

V

PFM REGULATOR

t

ON

OUTPUT VOLTAGE

V

OUT

RESET COMPARATOR

Output Voltage 0 < I

REF

Pulse Width 4.5 5 5.5 µs

Output Voltage -3 Suffix 3.2 3.3 3.4 V

Load Regulation See Figure 1, -3 Suffix 3.2 3.3 3.4 V

Undervoltage Lockout Threshold 0.85 0.95 V

DETECT Threshold 194 200 206 mV

< –5µA 190 200 210 mV

REF

tON = 0 at V

4.5µs £ tON £ 5.5µs -5 Suffix 4.85 5.0 5.15 V
at V

OUT(MIN)

VIN = 1.2V, I

See Figure 1, -3 Suffix 3.2 3.3 3.4 V
VIN = 2.4V, I

See Figure 1, -5 Suffix 4.85 5.0 5.15 V
VIN = 1.2V, I

See Figure 1, -5 Suffix 4.85 5.0 5.15 V
VIN = 2.4V, I

OUT(MAX)

OUT

OUT

OUT

OUT

,

£ 10mA

£ 65mA

£ 18mA

£ 85mA

DETECT Bias Current –100 100 nA

RESET Output High Voltage IOH = 100µA V

RESET Output Low Voltage IOL = -100µA 0.2 V

Note 1: Limits are guaranteed by 100% testing, sampling or correlation with worst case test conditions.

DATASHEET

July 2000

– 0.2 V

OUT

3