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L5953
MULTIPLE SWITCHING VOLTAGE REGULATOR
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L5953September 2003 PWM: ADJUSTABLE 2.5/10V - 1A
SWITCHING VOLTAGE REGULATOR EXTERNAL POWER MOS ABILITY FOR
OUTPUT CURRENT ENHANCEMENT SYNCHRONIZATION FUNCTION REG1- LINEAR LOW DROP 3.3/5V - 250mA
STBY VOLTAGE REGULATOR (LOW
CURRENT CONSUMPTION) with RESET REG2- LINEAR VOLTAGE REGULATOR 1.5V
to 3.3V EXTERNALLY ADJUSTABLE - 300mA
MAXIMUM CURRENT HSD1 : 500mA HIGH SIDE DRIVER HSD2 : 200mA HIGH SIDE DRIVER SPI INTERFACE SPI DIAGNOSTICS HSD1, HSD2 DOUBLE SWITCHING FREQUENCY SPI SELECTABLE DOUBLE INPUT LVW
SPI FUNCTIONS INPUT CONTROLS Turn-on/off PWM Turn-on/off REG2 Turn-on/off HSD1 Turn-on/off HSD2 Switching frequency selection f1- f2 OUTPUT FUNCTIONS: HSD1 & HSD2 short to gnd, open load and
short to battery (Test mode) Thermal warning
PROTECTIONS OVERVOLTAGE PROTECTION INTERNAL CURRENT LIMITING THERMAL SHUTDOWN ESD
DESCRIPTIONThe L5953 is the integration of one switching regula-
tor, two linear voltage regulators, two low voltage
warnings and two high side drivers. It has a stand-by
operation mode (low current consumption) where
only the stand-by voltage regulator plus the low volt-
age warnings are active. The other regulators and
high side drivers are controlled by the SPI interface.
PRODUCT PREVIEWMULTIPLE SWITCHING VOLTAGE REGULATOR
BLOCK DIAGRAM
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ABSOLUTE MAXIMUM RATINGS
THERMAL DATA
PIN CONNECTION
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PIN FUNCTION
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ELECTRICAL CHARACTERISTCS ( Tamb = 25°C, VDD = 14.4V)
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ELECTRICAL CHARACTERISTCS (continued)( Tamb = 25°C, VDD = 14.4V)
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DIAGNOSTIC PARAMETERS
ELECTRICAL CHARACTERISTCS (continued)( Tamb = 25°C, VDD = 14.4V)
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SPI INTERFACE
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Figure 1. AC Testing Input Output WaveformsI
Figure 2. SPI Clocking Scheme
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Figure 3. Output Timing
Figure 4. Serial Input Timing
FUNCTIONAL DESCRIPTION
REG1 Stand-by Regulator (Figure 5)The stand-by regulator output voltage can be 5V or 3.3V. It is externally selectable by means of the ADJ pin:
- leaving the ADJ pin open, the output voltage is 5V;
- connecting the ADJ pin to the Vstby pin the output voltage becomes 3.3V.
This regulator is supplied by STCAP pin and provide the reset information.
It has a current protection which limits the maximum allowable output current.
Reset (Figure 6)The RES pin is an open collector that is activated (that is forced to zero) when the stand-by regulator is not in
regulation (including thermal shutdown and faults). The indication that REG1 is in regulation is delayed by a time
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set up by the external capacitor CT.
When the RES is switched on, HSD1, HSD2, REG2, PWM are turned off and until the RES is forced to zero
only the REG1 and low Voltage Warnings are active.
Low Voltage Warning(Figure 7)This circuit is able to sense two different voltages through external resistors to increase the overall flexibility.
If S1 pin voltage is higher than Vst, the output mos M1 is off: W1 is floating and can be pulled up by an external
resistor. If S1 pin voltage goes down and becomes lower than Vst, the mos M1 is turned on and forces W1 to
zero. The same thing happens for S2 - W2.
The outputs W1 and W2 can be connected together to get a single output.
REG2 Linear Voltage Regulator (Figure 5)REG2 is a linear voltage regulator with a dedicated supply pin VIN. The output voltage (between 1.5V and 3.3V)
is fixed by an external divider. It can be turned on/off by SPI. It has a current protection which limits the maximum
allowable output current.
High Side Drivers (Figure 8)Two high-side driver with charge pump controlled by SPI are available inside L5953. They are protected against
short to ground: the short circuit potection limits the maximum output current.
A diagnostic procedure is available to detect open load, short to battery and overcurrent.
Open load and short to battery can be reveal only in test mode while overcurrent is active only during normal
operationof the device. (see OPERATION -page 13
PWM Step Down Voltage Regulator (Figure 9)The switching regulator inside the L5953 is a voltage control mode (also known as "direct duty cycle") Buck reg-
ulator: the error signal coming from the error amplifier is compared with a sawtooth to set on and off times of the
power switch.
The feedforward control is introduced to get a quickly response to input voltage changes: the sawtooh has a
fixed frequency and an amplitude variable with the battery voltage.
Continuous mode operation is recommended in order to reduce the stress of the output capacitor and of the
free-wheeling diode.
The error amplifier (EA) is a voltage amplifier whose non-inverting input is fixed to the reference voltage (1.275V
bandgap voltage) and whose inverting input and output are externally available for feedback and frequency
compensation.
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Figure 5. Linear regulators - Internal pin connections
Figure 6. Reset Internal pin Connection
Figure 7. Low Voltage Warning Block Diagram.
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Figure 8. HSD - Internal pin connections
Figure 10. SPI & IRQ Internal pin connections
