ZETEX ZXLB1600 Technical data
ZXLB1600
LCD AND OLED BIAS BOOST CONVERTER - STN, CSTN SCREENS
DESCRIPTION
The ZXLB1600 inductive switching boost converter
accepts an input voltage of between 1.6V and 5.5V and
provides an adjustable output voltage of up to 28V for
LCD and OLED bias. The device contains an output
switch and a second switch to isolate the coil from the
input to provide true isolation in shutdown mode. The
output can be adjusted by means of an externally
applied dc voltage, a PWM control signal, or external
feedback resistors and can supply typically 10mA of
output current at maximum output voltage. Higher
current is available at lower output voltages.
The input voltage range accepts a number of battery
solutions, including dualdrycellandsingleLi-Ioncells
and PFM operation mode allows the output to be
regulated with high efficiency under light or no load
conditions.Theswitchingfrequencyrangepermitsthe
use of miniature surface mount inductors.
A low battery comparator is provided to indicate when
the input voltage has fallen to within ±2% of a preset
threshold. This threshold is set internally , but can be
adjusted externally to any voltage within the supply
voltage range.
TYPICAL APPLICATION CIRCUIT
FEATURES
Wide input voltage range: 1.6 to 5.5V
•
Adjustable output voltage up to 28V, using PWM
•
or analog control voltage
Internal PWM filter
•
True shutdown (output isolated from input)
•
Internal output switch and current sense
•
Low quiescent current: (75A max)
•
5A (max) shutdown current (including low
•
battery comparator)
Up to 500kHz switching frequency
•
High efficiency
•
Small MSOP10 package
•
Low external component count
•
APPLICATIONS
PDAs
•
•
Mobile phones - OLED sub displays
•
Digital cameras
•
Portable internet appliances
•
Palmtop computers
•
GPS terminals
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SEMICONDUCTORS
ZXLB1600
ABSOLUTE MAXIMUM RATINGS
(Voltages to GND unless otherwise stated)
Output voltage 30V
Input voltage 7V
Switch output current 500mA
Power dissipation 800mW
Operating temperature 0 to 70⬚C
Storage temperature -55 to 125⬚C
Junction temperature 150⬚C
ELECTRICAL CHARACTERISTICS
Test conditions unless otherwise stated: V
Symbol Parameter Conditions Min Typ Max Units
General
V
IN
I
IN
Input voltage
Supply current Shutdown
Quiescent VEN=VIN,I
Isolating switch
R
ISO
I
ISO
V
SW(max)
‘On’ resistance VEN=V
Leakage current VEN=0V 1 A
Maximum voltage on SW pin
during normal operation
LX Switch
I
LX
R
LX
I
LX(leak)
V
LX
Switch peak current limit
‘On’ resistance 0.5 2 ⍀
Switch leakage current 1 A
Operating voltage on LX pin -0.5 30 V
Controller output
V
I
OUT
⌬V
⌬V
f
LX
T
T
OUT
LNR
LDR
ON
OFF
Output voltage range V
Output current Lx = 22H, V
Line regulation I
Load regulation V
Operating frequency 500 kHz
Output ‘ON’ time LX output low 10 s
Output ‘OFF’ time LX output off 0.9 µs
Efficiency
Note:
1) Minimum supply voltage should be maintained above 2V for operation at minimum temperature.
2) Shutdown current includes the operating current for the low battery comparator, which remains active in shutdown mode.
3) This is the dc value. The dynamic value may exceed 350mA during normal operation, due to switching delays, coil inductance and supply
voltage.
4) Efficiency is dependent upon the choice of external components, input/output voltages and load current.(see typical operating curves).
(1)
(2)
(3)
(4)
= 3.0V, T
IN
AMB
= 25°C
1.6 5.5 V
VEN= 0V 3.5 5 A
switching
IN
OUT
= 0V, Not
30 75 A
0.7 2 ⍀
VIN+0.5 V
0.15 0.35 A
IN
= 28V 5 10 mA
OUT
= 1mA, 2V < VIN<5.5V 0.1 %/V
OUT
= 28V, 100A<I
OUT
< 5mA
Lx=22H, V
OUT
= 20V 80 %
OUT
0.15 %/mA
28 V
SEMICONDUCTORS
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ZXLB1600
ELECTRICAL CHARACTERISTICS (Cont.)
Test conditions unless otherwise stated: V
Symbol Parameter Conditions Min Typ Max Units
Output voltage control by dc voltage applied to ‘ADJ’ pin
V
ADJ (nom)
V
ADJ
I
ADJ
V
SENSE
Output voltage control by PWM signal applied to ‘EN’ input
∆T/T
f
LPF
A
LPF
Internal voltage setting resistors for output voltage
R1 Ref. Block diagram 317
R2 6.93 M⍀
Enable input
V
ENL
V
ENH
I
ENL
I
ENH
T
EN(hold)
Low-battery detection circuit
V
LBT
V
BLHYS
Ref
(LBD)
V
LBT (max)
I
BLOL
V
BLOL
I
BLOH
V
BLOH
Internal voltage setting resistors for low-battery detection circuit
R3 Ref. block diagram 1.56 M⍀
R4 2.44
Note:
5) This is the minimum PWM frequency to maintain a continuous output. Lower frequencies can be used, but will result in gated operation of
the device i.e. device enters shutdown when EN is low (see Note 6).
6) This is the time for which the device remains active after the EN pin has been driven low. This delay allows a continuous output to be
maintained during PWM mode operation at frequencies higher than 10kHz.
Internal reference voltage ‘ADJ’ pin floating, ‘EN’= V
Temperature coefficient of V
ADJ
External overdrive voltage range
on ‘ADJ’ pin for output voltage
control
Input current into V
pin 0.5<V
ADJ
Default Output voltage ‘ADJ’ pin floating, ‘EN’= V
PWM duty cycle range at ‘EN’
input
Internal low pass filter cut-off
frequency
Filter attenuation f=30kHz 52.5 dB
Low level Input voltage Device in shutdown 0.4 V
High level Input voltage Device active 1.4 Vin V
Low level input current VEN=0V -100 nA
High level input current VEN=V
Enable active hold time
(6)
Detection threshold VINfalling 1.94 2.02 V
Temperature coefficient of V
BLT
Hysteresis VINrising 20 mV
Internal reference voltage 1.21 V
Maximum voltage on LBT pin Vin-0.5 V
Low level output current Output ‘on’ 1 mA
Low level output voltage I
High level output current Output ‘off’ , V
High level output voltage Output ‘off’ 29 V
= 3.0V, T
IN
AMB
= 25°C
IN
1.23 V
40 ppm/⬚C
ADJ<VADJ (NOM)
(5)
10kHz
< f < 100kHz, V
IN
ENH=VIN
0.5 V
27 29 V
40 100 %
ADJ
(NOM)
-10 A
V
4 kHz
k⍀
IN
100 nA
VENswitched from high to low 120 s
20 ppm/⬚C
= 0.5mA 0.4 V
BLOL
= 29V 2 A
BLOH
M⍀
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SEMICONDUCTORS
ZXLB1600
PIN CONNECTIONS
PIN DESCRIPTION
Pin # Name Description
1 ADJ Internal (or external) reference voltage.
2 EN Enable input (active high)
3 VIN Input voltage
4 SW Output of high side PMOS isolation switch
5 SENSE Output voltage sense
6 LX Output of NMOS switch
7 LBF Low battery flag output: open drain
8 GND Ground
9 FB Voltage feedback pin for output (threshold 1.23V)
10 LBT Low battery flag threshold adjust input
Can be overdriven to adjust output voltage
Also used to adjust output voltage by PWM signal
(active low for low battery voltage)
Active when EN is high or low
(threshold 1.21V)
ORDERING INFORMATION
DEVICE DEVICE DESCRIPTION TEMPERATURE
ZXLB1600X10TA Boost converter for LCD bias in MSOP10 0 ⬚C to 70 ⬚C ZXLB1600
ZXLB1600X10TC Boost converter for LCD bias in MSOP10 0 ⬚C to 70 ⬚C ZXLB1600
TA reels 1k,
TC reels 4k devices.
RANGE
ISSUE 3 - SEPTEMBER 2003
SEMICONDUCTORS
4
PART MARK
BLOCK DIAGRAM
ZXLB1600
Device description
The device is a flyback boost converter, working in
discontinuous mode.
With reference to the chip block diagram and typical
application circuit, the operation of the device is as
follows:
Control loop
When 'EN' is high, the control circuits become active. The
high side of the coil is connected to the input via a large
PMOSisolatingswitch (MP)and thelow side toground via
NDMOS transistor (MN). The current in the coil is allowed
to build up to an internally defined level (nominally 200 to
300mA) before MN is turned off. The energy stored in the
coil is then transferred to the output capacitor (C2) via
diode(D1). The outputvoltage is sensedat pin 'SENSE' by
internal resistors R1 and R2 (which may be shunted
externallyat pin'FB') and comparedto areference voltage
(1.23V nominal). A comparator senses when the output
voltage is above that set by the reference and its output is
used to control the 'off' time of the output switch. The
control loop is self-oscillating, producing pulses of 10s
maximumduration (switch'on'), at afrequency thatvaries
in proportion to the output load current. The minimum
'off'time of theoutput switch is fixed at1.25s nominal,to
allow time for the coil's energy to be dissipated before the
switch is turned on again. This maintains stable and
efficient operation.
ISSUE 3 - SEPTEMBER 2003
Setting output voltage
With external voltage
The output voltage is equal to the voltage present on
the 'ADJ' pin of the device multiplied by the internal
resistor network factor (R1+R2)/R1. The ADJ pin is
connected to the internal reference voltage of value
V
ADJ(nom)
28V. However, if required, the ADJ pin may be
overdrivenwith anexternal dc voltageV
adjust the output voltage to a value lower than the
default value.
and by default will give a nominal output of
,in orderto
ADJ
5
SEMICONDUCTORS
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