Micro Linear Corporation ML4828IS, ML4828CP, ML4828CS, ML4828IP Datasheet

May 1997

ML4828*

BiCMOS Phase Modulation/Soft Switching Controller

GENERAL DESCRIPTION

The ML4828 is a complete BiCMOS phase modulation
control IC suitable for full bridge soft switching converters.
Unlike conventional PWM circuits, the phase modulation
technique allows for zero voltage switching (ZVS)
transitions and square wave drive across the transformer.
The IC modulates the phases of the two sides of the bridge
to control output power.

The ML4828 can be operated in either voltage or current
mode. Both cycle-by-cycle current limit, integrating fault
detection, and soft start reset are provided. The under­voltage lockout circuit features a 1.5V hysteresis with a
low starting current to allow off-line start up with a bleed

FEATURES

■ 5V BiCMOS for low power and high frequency

(1MHz) operation

■ Full bridge phase modulation zero voltage switching

circuit with independent programmable delay times

■ Current or voltage mode operation capability

■ Cycle-by-cycle current limiting with integrating fault

detection and restart delay

■ Can be externally synchronized

■ Four 3Ω CMOS output drivers

■ Under-voltage lockout circuit with 1.5V hysteresis

resistor. A shutdown function powers down the IC, putting
it into a low quiescent state.

The circuit can be operated at frequencies up to 1MHz.
The ML4828 contains four high current CMOS outputs
which feature high slew rate with low cross conduction. *Some Packages Are End Of Life

BLOCK DIAGRAM

V

V

CC

14

REF

5

SYNC RTC

643

T

2.5V REF

SDN DRIVER

EA+

EA–

EAO

RAMP

SS

RST

I

LIM

19

10

9

8

11

7

1.25V

12

20

2.5V

1V

+
–

UVLO

+

–

+

–

ERROR

AMP

I

LIM

IRST

ISS

FAULT
LOGIC

–
+

Q

Q

ΦMOD

S

R

OSC

DELAY A

Q

T

Q

Q

R

Q

S

GND

DELAY B

1

R

A

217

R

B

DRIVER

DRIVER

DRIVER

A1

18

A2

16

B1

15

13

B2

1

ML4828

PIN CONNECTION

ML4828

20-Pin DIP (P20)

20-Pin SOIC (S20)

1

RA

2

R



B

3

R



T

4

C



T

5

REF

EA0
EA–
EA+

6

7

SS

8

9

10

TOP VIEW

SYNC

I

LIM

SDN
A1
GND
A2
B1
V

CC

B2
RST
RAMP





20

19

18

17

16

15

14

13

12

11

PIN DESCRIPTION

PIN NAME DESCRIPTION

1R

A

2R

B

3R

T

4C

T

5 REF 2.5V reference voltage.
6 SYNC Synchronization input to oscillator.
7 SS Soft start capacitor connection.
8 EAO Error amplifier output.
9 EA- Error amplifier inverting input.

10 EA+ Error amplifier non-inverting input.

A1 and A2 delay programming
resistor.

B1 and B2 delay programming
resistor .

Oscillator charge current
programming resistor.

Oscillator timing capacitor.

PIN NAME DESCRIPTION

11 RAMP RC network for phase modulator

ramp input.

12 RST RC network for reset and integrating

fault detect.
13 B2 B2 driver output.
14 V

CC

Power supply
15 B1 B1 driver output.
16 A2 A2 driver output.
17 GND Ground.
18 A1 A1 driver output.
19 SHDN Active low device shutdown.
20 I

LIMIT

Current limit control input

2

ML4828

ABSOLUTE MAXIMUM RATINGS

Soft Start Discharge Current ...................................... 5mA

CT Charging Current................................................. –1mA

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

CC

Output Current, Source or Sink (A1, A2, B1, B2)

Junction Temperature .............................................. 150°C

Storage Temperature Range ...................... –65°C to 150°C

Lead Temperature (Soldering 10 sec.) ...................... 260°C

Thermal Resistance (θ

)

JA

Plastic DIP ........................................................ 67°C/W

Plastic SOIC ..................................................... 95°C/W

Pulse (0.5 µs) ......................................................... 1.0A

Analog Inputs (EA+, EA–, EAO,

RST, RAMP, RST)............................ –0.3V to VCC + 0.3V

RT Source Current .................................................... –1mA

Error Amplifier Output Current ................................ ±2mA

OPERATING CONDITIONS

Temperature Range

ML4828CX ................................................. 0°C to 70°C

ML4828IX ............................................... –40°C to 85°C

ELECTRICAL CHARACTERISTICS

Unless otherwise specified, RA = R
(Notes 1,2)

PARAMETER CONDITIONS MIN TYP. MAX UNITS

OSCILLATOR

Initial Accuracy TA = 25°C 340 360 380 kHz

Voltage Stability 4.5V < VCC < 5.5V 4 5.3 %/V

Temperature Stability 2%

= 33.3kΩ, RT = 16kΩ, C

B

= 270PF, V

T

= 5V, TA = Operation Temperature Range

CC

Total Variation Line, temp. 325 400 kHz

CT Discharge Current VCT = 2V 1.15 1.5 mA

Ramp Peak 2.6 V

Ramp Valley 1.12 V

REFERENCE

Initial Accuracy TA = 25°C, IO = 250µA 2.475 2.5 2.525 V

Line Regulation 4.5V < VCC < 6.5V ±0.2 ±1 %/V
Load Regulation 100µA to 1mA ±0.5 ±6mV

Temperature Stability 0.45 %

Total Variation Line, Load, & Temp 2.44 2.54 V

Long Term Stability TJ = 125°C, 1000 hrs 5 25 mV

Short Circuit Current V

ERROR AMPLIFIER

Input Offset Voltage –20 20 mV

Input Common-Mode Range 0 1.75 V

Open Loop Gain 1V < VO < 2.7V 60 80 dB

PSRR 4.5V < V

Output Sink Current VO = 0.5V 1.2 1.9 mA

= 0V –10 –23 –35 mA

REF

< 6.5V 60 80 dB

CC

Output Source Current VO= 2.7V –0.35 –1.1 mA

Output High Voltage I

Output Low Voltage I

Unity Gain Bandwidth 7 10 MHz
Slew Rate 510 V/µs

= –500µA 2.6 2.85 V

SOURCE

= 500µA 0.1 0.2 V

SINK

3

ML4828

ELECTRICAL CHARACTERISTICS (Continued)

PARAMETER CONDITIONS MIN TYP. MAX UNITS

PHASE MODULATOR

EAO Zero Duty Cycle Threshold VRT = 0V 0 0.5 0.9 V

RAMP Delay to Output 50 80 ns

RAMP Discharge Current 48 95 mA

SOFT-START

Charge Current VSS = 4V –25 –50 µA

Discharge Current VSS = 1V 6 10 13.2 mA

CURRENT LIMIT/SHUTDOWN

Current Limit Threshold 0.9 1.0 1.1 V

Pin 20 Delay to Output (Note 1) 50 ns

Pin 12 Shutdown Threshold 1.0 1.1 1.5 V

Pin 12 Restart Threshold 2.2 2.4 2.6 V
Pin 12 Charging Current –350 –460 –550 µA

SDN Shutdown Threshold 1.05 1.6 2.05 V

OUTPUT

Output Low Level I

Output High Level I

= 20 mA 0.01 0.1 V

OUT

I

= 100 mA 0.1 0.3 V

OUT

= –20 mA 4.9 4.95 V

OUT

I

= –100 mA 4.6 4.7 V

OUT

Rise/Fall Time CL = 1000pF, (Note 1) 5 7 ns

ZVS Programmable Delay 240 280 315 ns

Delay Mismatch 0ns

R

/RB Reference Voltage 2.45 2.5 2.55 V

A

UNDER VOLTAGE LOCKOUT

Start Threshold 5.1 5.85 6.6 V

Stop Threshold 4.1 4.2 4.3 V

SUPPLY

Start Up Current V

6V 0.6 1 mA

CC <

Shutdown Current 100 500 µA

I

CC

Note 1: Limits are guaranteed by 100% testing, sampling, or correlation with worst-case test conditions.
Note 2: V

must be brought above the UVLO start voltage (6V) before dropping to VCC = 5V to ensure start-up.

CC

V

= 5V, CL = 1000pF, TA = 25°C57mA

CC

4