ST L6599 User Manual

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Features

■ 50% duty cycle, variable frequency control of

resonant half-bridge

■ High-accuracy oscillator

■ Up to 500kHz operating frequency

■ Two-level OCP: frequency-shift and latched

shutdown

■ Interface with PFC controller

■ Latched disable input

■ Burst-mode operation at light load

■ Input for power-ON/OFF sequencing or

brownout protection

■ Non-linear soft-start for monotonic output

voltage rise

■ 600V-rail compatible high-side gate driver with

integrated bootstrap diode and high dV/dt immunity

■ -300/800mA high-side and low-side gate

drivers with UVLO pull-down

■ DIP-16, SO-16N packages

L6599

High-voltage resonant controller

DIP-16 SO-16N

Order code

Part number Package Packaging

L6599D SO-16N Tube

L6599TR SO-16N Tape and reel

L6599N DIP-16 Tube

Applications

■ LCD & PDP TV

■ Desktop PC, entry-level server

■ Telecom SMPS

■ AC-DC adapter, open frame SMPS

Block diagram

Vcc

DIS

STBY 5

RFmin

Css

1.85V

1.25V

DISABLE

Ifmin

VCO

UVLO

DIS

S Q

STANDBY

CONTROL

LOGIC

DELAY

17V

DETECTION

UVLO

DEAD

TIME

SYNCHRONOUS

BOOTST RAP DIODE

DRIVING

LOGIC

ISEN_DIS

1.2 5V

6.3V

µA

LINE

Q S

HVG

DRIVER

LEVEL

SHIFTER

LVG DR IVER

UVLO

LINE _OK

ISEN_DIS

STANDBY

1.5V

0.8V

DIS

May 2006 Rev 1 1/36

H.V.

BOOT

HVG

OUT

LV G

GND

ISEN

PFC _STOP

BOOT

LC T AN CIRCUIT

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Contents L6599

Contents

1 Device description . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2 Pin Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.1 Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

2.2 Functions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

3 Typical system block diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

4 Electrical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4.1 Maximum ratings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

4.2 Thermal data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

5 Electrical characteristics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8

6 Typical electrical performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

7 Application information . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

7.1 Oscillator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

7.2 Operation at no load or very light load . . . . . . . . . . . . . . . . . . . . . . . . . . . 18

7.3 Soft-start . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

7.4 Current sense, OCP and OLP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23

7.5 Latched shutdown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

7.6 Line sensing function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27

7.7 Bootstrap section . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29

7.8 Application example . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

8 Package mechanical data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

9 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

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L6599 Device description

1 Device description

The L6599 is a double-ended controller specific for the resonant half-bridge topology. It provides 50% complementary duty cycle: the high-side switch and the low-side switch are driven ON 180° out-of-phase for exactly the same time. Output voltage regulation is obtained by modulating the operating frequency. A fixed deadtime inserted between the turn-OFF of one switch and the turn-ON of the other one guarantees soft-switching and enables high-frequency operation.

To drive the high-side switch with the bootstrap approach, the IC incorporates a high-voltage floating structure able to withstand more than 600V with a synchronous-driven high-voltage DMOS that replaces the external fast-recovery bootstrap diode.

The IC enables the designer to set the operating frequency range of the converter by means of an externally programmable oscillator.

At start-up, to prevent uncontrolled inrush current, the switching frequency starts from a programmable maximum value and progressively decays until it reaches the steady-state value determined by the control loop. This frequency shift is non linear to minimize output voltage overshoots; its duration is programmable as well.

The IC can be forced to enter a controlled burst-mode operation at light load, so as to keep converter's input consumption to a minimum.

IC's functions include a not-latched active-low disable input with current hysteresis useful for power sequencing or for brownout protection, a current sense input for OCP with frequency shift and delayed shutdown with automatic restart.

A higher level OCP latches off the IC if the first-level protection is not sufficient to control the primary current. Their combination offers complete protection against overload and short circuits. An additional latched disable input (DIS) allows easy implementation of OTP and/or OVP.

An interface with the PFC controller is provided that enables to switch off the pre-regulator during fault conditions, such as OCP shutdown and DIS high, or during burst-mode operation.

3/36

Pin Settings L6599

2 Pin Settings

2.1 Connection

Figure 1. Pin Connection (Top view)

Css

DELAY

RFmin

STBY

ISEN

LINE

DIS

2.2 Functions

Table 1. Pin functions

N. Name Function

Soft start. This pin connects an external capacitor to GND and a resistor to RFmin (pin 4) that set both the maximum oscillator frequency and the time constant for the frequency shift

2DELAY

3CF

that occurs as the chip starts up (soft-start). An internal switch discharges this capacitor every time the chip turns OFF (V

1.5V, DELAY > 3.5V) to make sure it will be soft-started next, and when the voltage on the current sense pin (ISEN) exceeds 0.8V, as long as it stays above 0.75V.

Delayed shutdown upon overcurrent. A capacitor and a resistor are connected from this pin to GND to set both the maximum duration of an overcurrent condition before the IC stops switching and the delay after which the IC restarts switching. Every time the voltage on the ISEN pin exceeds 0.8V the capacitor is charged by an internal 150µA current generator and is slowly discharged by the external resistor. If the voltage on the pin reaches 2V, the soft start capacitor is completely discharged so that the switching frequency is pushed to its maximum value and the 150µA is kept always on. As the voltage on the pin exceeds 3.5V the IC stops switching and the internal generator is turned OFF, so that the voltage on the pin will decay because of the external resistor. The IC will be soft-restarted as the voltage drops below 0.3V. In this way, under short circuit conditions, the converter will work intermittently with very low input average power.

Timing capacitor. A capacitor connected from this pin to GND is charged and discharged by internal current generators programmed by the external network connected to pin 4 (RFmin) and determines the switching frequency of the converter.

< UVLO, LINE < 1.25V or > 6V, DIS > 1.85V, ISEN >

VBOOT

HVG

OUT

N.C.

Vcc

LVG

GND

PFC_STOP

4/36

L6599 Pin Settings

Table 1. Pin functions

Minimum oscillator frequency setting. This pin provides a precise 2V reference and a resistor connected from this pin to GND defines a current that is used to set the minimum oscillator frequency. To close the feedback loop that regulates the converter output voltage by

4RFmin

5STBY

6 ISEN

7LINE

8DIS

9PFC_STOP

10 GND

modulating the oscillator frequency, the phototransistor of an optocoupler will be connected to this pin through a resistor. The value of this resistor will set the maximum operating frequency. An R-C series connected from this pin to GND sets frequency shift at start-up to prevent excessive energy inrush (soft-start).

Burst-mode operation threshold. The pin senses some voltage related to the feedback control, which is compared to an internal reference (1.25V). If the voltage on the pin is lower than the reference, the IC enters an idle state and its quiescent current is reduced. The chip restarts switching as the voltage exceeds the reference by 50mV. Soft-start is not invoked. This function realizes burst-mode operation when the load falls below a level that can be programmed by properly choosing the resistor connecting the optocoupler to pin RFmin (see block diagram). Tie the pin to RFmin if burst-mode is not used.

Current sense input. The pin senses the primary current though a sense resistor or a capacitive divider for lossless sensing. This input is not intended for a cycle-by-cycle control; hence the voltage signal must be filtered to get average current information. As the voltage exceeds a 0.8V threshold (with 50mV hysteresis), the soft-start capacitor connected to pin 1 is internally discharged: the frequency increases hence limiting the power throughput. Under output short circuit, this normally results in a nearly constant peak primary current. This condition is allowed for a maximum time set at pin 2. If the current keeps on building up despite this frequency increase, a second comparator referenced at 1.5V latches the device off and brings its consumption almost to a “before start-up” level. The information is latched and it is necessary to recycle the supply voltage of the IC to enable it to restart: the latch is removed as the voltage on the Vcc pin goes below the UVLO threshold. Tie the pin to GND if the function is not used.

Line sensing input. The pin is to be connected to the high-voltage input bus with a resistor divider to perform either AC or DC (in systems with PFC) brownout protection. A voltage below 1.25V shuts down (not latched) the IC, lowers its consumption and discharges the soft-start capacitor. IC’s operation is re-enabled (soft-started) as the voltage exceeds 1.25V. The comparator is provided with current hysteresis: an internal 15µA current generator is ON as long as the voltage applied at the pin is below 1.25V and is OFF if this value is exceeded. Bypass the pin with a capacitor to GND to reduce noise pick-up. The voltage on the pin is top-limited by an internal zener. Activating the zener causes the IC to shut down (not latched). Bias the pin between 1.25 and 6V if the function is not used.

Latched device shutdown. Internally the pin connects a comparator that, when the voltage on the pin exceeds 1.85V, shuts the IC down and brings its consumption almost to a “before start-up” level. The information is latched and it is necessary to recycle the supply voltage of the IC to enable it to restart: the latch is removed as the voltage on the V the UVLO threshold. Tie the pin to GND if the function is not used.

Open-drain ON/OFF control of PFC controller. This pin, normally open, is intended for stopping the PFC controller, for protection purpose or during burst-mode operation. It goes low when the IC is shut down by DIS > 1.85V, ISEN > 1.5V, LINE > 6V and STBY < 1.25V. The pin is pulled low also when the voltage on pin DELAY exceeds 2V and goes back open as the voltage falls below 0.3V. During UVLO, it is open. Leave the pin unconnected if not used.

Chip ground. Current return for both the low-side gate-drive current and the bias current of the IC. All of the ground connections of the bias components should be tied to a track going to this pin and kept separate from any pulsed current return.

pin goes below

5/36

Typical system block diagram L6599

Table 1. Pin functions

Low-side gate-drive output. The driver is capable of 0.3A min. source and 0.8A min. sink

11 LVG

12 V

13 N.C.

14 OUT

15 HVG

16 VBOOT

peak current to drive the lower MOSFET of the half-bridge leg. The pin is actively pulled to GND during UVLO.

Supply Voltage of both the signal part of the IC and the low-side gate driver. Sometimes a small bypass capacitor (0.1µF typ.) to GND might be useful to get a clean bias voltage for the signal part of the IC.

High-voltage spacer. The pin is not internally connected to isolate the high-voltage pin and ease compliance with safety regulations (creepage distance) on the PCB.

High-side gate-drive floating ground. Current return for the high-side gate-drive current. Layout carefully the connection of this pin to avoid too large spikes below ground.

High-side floating gate-drive output. The driver is capable of 0.3A min. source and 0.8A min. sink peak current to drive the upper MOSFET of the half-bridge leg. A resistor internally connected to pin 14 (OUT) ensures that the pin is not floating during UVLO.

High-side gate-drive floating supply Voltage. The bootstrap capacitor connected between this pin and pin 14 (OUT) is fed by an internal synchronous bootstrap diode driven in-phase with the low-side gate-drive. This patented structure replaces the normally used external diode.

3 Typical system block diagram

Figure 2. Typical system block diagram

6/36

L6599 Electrical data

4 Electrical data

4.1 Maximum ratings

Table 2. Absolute maximum ratings

Symbol Pin Parameter Value Unit

BOOT

OUT

PFC_STOP

LINEmax

RFmin

/dt

16 Floating supply voltage -1 to 618 V

14 Floating ground voltage

14 Floating ground max. slew rate 50 V/ns

IC Supply voltage (I

≤ 25 mA)

9 Maximum voltage (pin open)

9 Maximum sink current (pin low) Self-limited A

7 Maximum pin voltage (Ipin ≤ 1mA) Self-limited V

4 Maximum source current 2 mA

1 to 6, 8 Analog inputs & outputs -0.3 to 5 V

Note: ESD immunity for pins 14, 15 and 16 is guaranteed up to 900V

4.2 Thermal data

Table 3. Thermal data

Symbol Description Value Unit

thJA

STG

TOT

Max. thermal resistance junction to ambient (DIP16) 80

Max. thermal resistance junction to ambient (SO16) 120

Storage temperature range -55 to 150 °C

Junction operating temperature range -40 to 150 °C

Recommended max. power dissipation @T

= 70°C (DIP16)

= 50°C (SO16)

BOOT

-18

-3 to V

Self-limited V

-0.3 to V

°C/W

0.83

7/36

Electrical characteristics L6599

5 Electrical characteristics

TJ = 0 to 105°C, V R

= 12kΩ; unless otherwise specified.

RFmin

= 15V, V

BOOT

= 15V, C

HVG

= C

= 1nF; CF = 470pF;

LVG

Table 4. Electrical characteristics

Symbol Parameter Test condition Min Typ Max Unit

IC supply voltage

CC(ON)

CC(OFF)

Hys Hysteresis 2.55 V

Supply current

start-up

Operating range After device turn-on 8.85 16 V

Turn-ON threshold Voltage rising 10 10.7 11.4 V

Turn-OFF threshold Voltage falling 7.45 8.15 8.85 V

VCC clamp voltage

Start-up current

Quiescent current

Operating current

Residual consumption

Iclamp = 10mA 16 17 17.9 V

Before device turn-ON

= V

Device ON, V

CC(ON)

- 0.2V

STBY

= 1V

Device ON, V

= V

STBY

DIS

> 3.5V or V or V

RFmin

> 1.85V or V

LINE

= V

LINE

clamp

DELAY

< 1.25 V

200 250 µA

1.5 2 mA

3.5 5 mA

300 400 µA

High-side floating gate-drive supply

pin leakage

LKBOOT

LKOUT

DS(on)

BOOT

current

OUT pin leakage current

Synchronous bootstrap diode ON-resistance

BOOT

OUT

LVG

Overcurrent comparator

ISEN

ISENx

LEB

Input bias current

Leading edge blanking

Frequency shift threshold

ISEN

After V low-to-high transition

Voltage rising

Hysteresis Voltage falling 50 mV

ISENdis

(H-L)

Latch OFF threshold

Voltage rising

Delay to output 300 400 ns

8/36

= 580V

= 562V

= High

= 0 to V

HVG

ISENdis

and V

(1)

LVG

5 µA

150 Ω

-1 µA

250 ns

0.76 0.8 0.84 V

1.44 1.5 1.56 V

L6599 Electrical characteristics

Table 4. Electrical characteristics

Symbol Parameter Test condition Min Typ Max Unit

Line sensing

Voltage rising or falling

(1)

VCC > 5V, V

= 1mA

LINE

= 0.3V

1.2 1.25 1.3 V

12 15 18 µA

6 8 V

Hyst

clamp

Threshold voltage

Current hysteresis

Clamp level

DIS function

DIS

Input bias current

Disable threshold

= 0 to Vth

DIS

Voltage rising

(1)

1.77 1.85 1.93 V

Oscillator

D Output duty cycle Both HVG and LVG 48 50 52 %

58.2 60 61.8

osc

Oscillation frequency

RFmin

= 2.7 kΩ

240 250 260

Maximum recommended

CFp

CFv

REF

MIN

Dead-time Between HVG and LVG 0.2 0.3 0.4 µs

Peak value 3.9 V

Valley value 0.9 V

Voltage reference at pin 4

(1)

1.92 2 2.08 V

Current mirroring ratio 1 A/A

Timing resistor range 1 100 kΩ

-1 µA

kHz

500 kHz

PFC_STOP function

leak

High level leakage current

Low saturation level

PFC_STOP

DIS

PFC_STOP

DIS

= 0V

= 2V

= VCC,

=1mA,

1 µA

0.2 V

Soft-start function

leak

R Discharge resistance

Open-state current V(Css) = 2V 0.5 µA

ISEN

> V

ISENx

120 Ω

Standby function

= 0 to Vth

DIS

Input Bias Current

Disable threshold

DIS

Voltage falling

(1)

-1 µA

1.2 1.25 1.3 V

Hys Hysteresis Voltage rising 50 mV

9/36

Electrical characteristics L6599

Table 4. Electrical characteristics

Symbol Parameter Test condition Min Typ Max Unit

Delayed shutdown function

leak

CHARGE

Vth

Open-state current V(DELAY) = 0 0.5 µA

Charge current

Threshold for forced

V V

Voltage rising

DELAY

ISEN

= 1V,

= 0.85V

operation at max. frequency

Vth

Shutdown threshold

Restart threshold

Voltage rising

Voltage falling

Low - side gate driver (voltages referred to GND)

= 200mA

LVG L

LVG H

sourcepk

sinkpk

Output low voltage

Output high voltage

Peak source current -0.3 A

Peak sink current 0.8 A

Fall time 30 ns

Rise time 60 ns

UVLO saturation

sink

source

sink

= 5mA

= 0 to V

= 2mA

High-side gate driver (voltages referred to OUT)

(1)

CC(ON)

100 150 200 µA

1.92 2 2.08 V

3.3 3.5 3.7 V

0.25 0.3 0.35 V

1.5 V

12.8 13.3 V

1.1 V

HVGL

HVGH

sourcepk

sinkpk

Output low voltage

Output high voltage

Peak source current -0.3 A

Peak sink current 0.8 A

Fall time 30 ns

Rise time 60 ns

sink

source

HVG-OUT pull-down 25 kΩ

1. Values traking each other

10/36

= 200 mA

= 5 mA

1.5 V

12.8 13.3 V

L6599 Typical electrical performance

6 Typical electrical performance

Figure 3. Device consumption vs

supply voltage

Figure 5. VCC clamp voltage vs

junction temperature

Figure 4. IC consumption vs

junction temperature

Figure 6. UVLO thresholds vs

junction temperature

11/36

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