MAX1549ETL Datasheet, PDF (11/35 Pages) Maxim Integrated Products – Dual, Interleaved, Fixed-Frequency Step-Down Controller with a Dynamically Adjustable Output

Dual, Interleaved, Fixed-Frequency Step-Down
Controller with a Dynamically Adjustable Output
PIN
1
2, 20,
25, 31
3
4
5
6
7
8, 9
10
11
12
13
14
NAME
GND
FUNCTION
Analog Ground. Connect backside pad to GND.
Pin Description
N.C. Not Internally Connected
REF
VCC
CC1
ILIM1
ILIM2
G0, G1
FBLANK
FSEL
2.0V Reference Voltage Output. Bypass to analog ground with a 0.1µF or greater ceramic capacitor. The
reference can source up to 100µA for external loads. Loading REF degrades output voltage accuracy
according to the REF load-regulation error. The reference shuts down when both MAX1549 outputs are
disabled.
Analog Supply Input. Connect to the system supply voltage (+4.5V to +5.5V) through a series 20Ω
resistor. Bypass V_CC to analog ground with a 1µF or greater ceramic capacitor.
Integrator Capacitor Connection. Connect a 47pF to 1000pF (470pF typ) capacitor from CC1 to analog
ground (GND) to set the integration time constant for the main MAX1549 controller (OUT1).
Current-Limit Threshold Adjustment for Controller 1. The current-limit threshold defaults to 70mV if ILIM1
is connected to V_CC. In adjustable mode, the current-limit threshold across CSH1 and CSL1 is precisely
1/10th the voltage seen at ILIM1 over a 0.5V to 2.0V range. The logic threshold for switchover to the
70mV default value is approximately V_CC - 1V.
Current-Limit Threshold Adjustment for Controller 2. The current-limit threshold defaults to 70mV if ILIM2
is connected to V_CC. In adjustable mode, the current-limit threshold across CSH2 and CSL2 is precisely
1/10th the voltage seen at ILIM2 over a 0.5V to 2.0V range. The logic threshold for switchover to the
70mV default value is approximately V_CC - 1V.
Buffered N-Channel MOSFET Gate Inputs. See Table 4.
Fault-Blanking Select Input. This four-level logic input enables or disables fault blanking and sets the
minimum forced-PWM operation time (tFBLANK). When fault blanking is enabled, the MAX1549 blanks
the PGOOD1 output and main (OUT1) controller’s OVP/UVP fault protection for the selected time period
after the controller detects a transition on G0 or G1. Additionally, the main controller enters forced-PWM
mode for the duration of tFBLANK anytime G0 or G1 changes states.
OUT1 fault protection and PGOOD1 blanking:
V_CC = 150µs, open = 100µs, REF = 50µs, GND = blanking disabled
Automatic forced-PWM transition operation (OUT1 only):
V_CC = 150µs, open = 100µs, REF = 50µs, GND = 100µs
Frequency-Select Input. This four-level logic input sets the controller’s switching frequency. Connect to
GND, REF, V_CC, or leave FSEL unconnected (open) to select the following typical switching frequencies:
V_CC = 400kHz, open = 300kHz, REF = 200kHz, GND = 100kHz
ON1
OUT1 Enable Input. Pull to GND to shut down controller 1 (OUT1). Connect to V_CC for normal operation.
The output is discharged through a 12Ω resistor between OUT1 and GND, and DL1 is forced high after
VOUT1 drops below 0.3V. A rising edge on ON1 or ON2 clears the fault-protection latch.
ON2
CSH2
OUT2 Enable Input. Pull to GND to shut down controller 2 (OUT2). Connect to V_CC for normal operation.
The output is discharged through a 12Ω resistor between OUT2 and GND, and DL2 is forced high after
VOUT2 drops below 0.3V. A rising edge on ON1 or ON2 clears the fault-protection latch.
Positive Current-Sense Input for Controller 2. Connect to the positive terminal of the current-sense
element. Figure 8 describes current-sensing options. The PWM controller does not begin a cycle unless
the current sensed is less than the current-limit threshold programmed at ILIM2.
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